3 science activities due in 28 hours

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(1) Properties of Soil: Agriculture and Water Availability Impacts Laboratory

Prior to beginning work on this assignment, read the Properties of Soil: Agricultural and Water Availability Impacts investigation manual. This lab enables you to analyze the natural porosity and particle size of soil samples along with the chemical composition and profile of different soil types.

The Process

Take the required photos and complete all parts of the lab assignment (calculations, data tables, etc.). Use the Lab Worksheet as a resource to complete the Lab Report Template. Transfer any answers and visual elements from the Lab Worksheet into the Lab Report  Template. You will submit the Lab Report Template through Waypoint in the classroom.

The Assignment

Make sure to complete all of the following items before submission:

  • Before you begin the assignment, read the Properties of Soil: Agricultural and Water Availability Impacts manual; you may also wish to review SCI207 – The Scientific Method (Links to an external site.) presentation video.
  • Complete all activities using the materials that you supply. Photograph each activity following these instructions:
    • When taking lab photos, you need to include in each image a strip of paper with your name and the date clearly written on it.
  • Use the Lab Worksheet as a resource to complete the Lab Report Template.
  • Must use at least two credible sources outside of the textbook and lab manual.
  • Submit your completed “Lab Report” via Waypoint.

 

(2)Sustainable Living Guide Contributions: Sustaining Our Agricultural Resources

(the term selected from this assignment is – community supported agriculture)

Prior to beginning work on this assignment, read Chapters 3 and 4 in your course textbook. The purpose of this assignment is twofold: first, to enable you to explore a term (concept, technique, place, etc.) related to this week’s theme of sustaining our agricultural resources; second, to provide your second contribution to a collective project, the Class Sustainable Living Guide. Your work this week, and in the weeks that follow, will be gathered (along with that of your peers) into a master document you will receive a few days after the end of the course. The document will provide everyone with a variety of ideas for how we can all live more sustainably in our homes and communities.

To complete this assignment,

  • Select a term from the list of choices in the Week 2 – Term Selection Table located in the course. Type your name in the table, next to the word that you would like to choose.
    • Do not select a term that a classmate has already chosen; only one student per term. If you choose a term that is hyperlinked to a source, that term is one that is not mentioned in our textbook. Instead of being required to use the text as your third source for completing the assignment, you will be expected to use the hyperlinked source provided for you.
  • Download the Week 2 Assignment Template available in the course and replace the guiding text with your own words based upon your online research.
    • Please do not include a cover page. All references, however, should be cited in your work and listed at the end, following APA Style expectations.

In the template, you will

  • Define the term thoroughly, in your own words.
  • Explain the importance of the term using evidence.
  • Discuss how the term affects living things and the physical world.
  • Suggest two specific actions that can be taken to promote environmental sustainability in relation to the term.
  • Explain exactly how those actions will aid in safeguarding our environment in relation to your chosen term.
  • Provide detailed examples to support your ideas.

The Sustainable Living Guide Contributions: Sustaining Our Agricultural Resources paper

 

(3) Week 2: Ecological Footprint Footprint Update and Course Reflection

Prior to working on this journal, read Chapters 3 and 4 in your course textbook.

Throughout this course, you are keeping a journal about your experience in the class. The purpose of this activity is to enable you to reflect on your learning: what new things you have discovered, what surprises you have encountered, what topics or ideas you have found particularly challenging, and how the course is going for you. Last week you began the Environmental Footprint Reduction Project. This week you will begin using this journal as a space for a progress report on your efforts. Your entries will be evaluated in terms of how well they met the topic and length requirements, and your writing clarity. Your entries should be a minimum of one typed page each (double-spaced, Times New Roman, 12-point font) and will be submitted through Waypoint.

Complete the following:

  • In the first paragraph or two of your journal entry this week, provide a status report on your Ecological Footprint Reduction Project. Have you encountered success with implementing your intended changes? What challenges have you encountered? What have you learned so far from this activity?
  • In another one or two paragraphs, share your thoughts about the second week of class. What did you learn? What experiences stand out for you? What tasks or content did you find difficult or frustrating? What activities did you find surprising or exciting? Looking ahead, what are your intrigued or concerned by in the third week of the course?

 

Required Resources

Text

Bensel, T., & Carbone, I. (2020). Sustaining our planet. Retrieved from https://content.ashford.edu

  • Chapter 3: Managing Our Population and Consumption
  • Chapter 4: Sustaining Our Agricultural Resources

Supplemental Material

Carolina Distance Learning. (n.d.). Properties of soil: Agricultural and water availability impacts [Investigation manual]. Retrieved from https://ashford.instructure.com

  • The Properties of Soil: Agricultural and Water Availability Impacts investigation manual is available in the online classroom. This lab manual provides background information on soil properties and will assist you in your Properties of Soil: Agricultural and Water Availability Impacts Laboratory assignment.

Laboratory Supplies

Carolina Biological Supply Lab Kit  (Links to an external site.)

  • This lab kit provides lab supplies and materials for the hands-on labs that you will conduct for this course. Although the lab kit provides most of the lab supplies for the labs, there will be materials that you need to purchase independently for a few labs. Be sure to prepare a list of what you will need to purchase independently by viewing the lab investigation manuals and lab kits in advance. To see a checklist of the additional lab supplies that you will need each week for this course, access the Additional Lab Supplies Checklist.

Recommended Resources

Article

FoodPrint. (n.d.). Sustainable agriculture vs. industrial agriculture (Links to an external site.). Retrieved from https://foodprint.org/issues/sustainable-agriculture-vs-industrial-agriculture/?cid=246

  • This web page provides information about the basic elements of sustainable agriculture and may assist you in your Sustainable Living Guide Contributions: Sustaining our Agricultural Resources Assignment.
    Accessibility Statement does not exist.
    Privacy Policy (Links to an external site.)

Multimedia

Ashford University. (2018). SCI207 – The scientific method (Links to an external site.). Retrieved from https://ashford.mediaspace.kaltura.com/media/SCI207+-+THE+SCIENTIFIC+METHOD/1_5325onvq

  • This video provides information on the scientific method that will assist you in completing your Stream Morphology laboratory activity this week. This video has closed captioning.

Happen Films. (2017, May 21). Organic sustainable farming is the future of agriculture | The future of food (Links to an external site.) [Video file]. Retrieved from https://youtu.be/hWkYtZxpQUo

Web Pages

University of California Davis, Agricultural Sustainability Institute. (n.d.). What is sustainable agriculture (Links to an external site.). Retrieved from http://asi.ucdavis.edu/programs/sarep/about/what-is-sustainable-agriculture

Union of Concerned Scientists. (n.d.). What is sustainable agriculture? (Links to an external site.) Retrieved from https://www.ucsusa.org/food-agriculture/advance-sustainable-agriculture/what-is-sustainable-agriculture#.W1Ekbdgzqu4

  • This web page provides information about sustainable agricultural practices and may assist you in your Sustainable Living Guide Contributions: Sustaining our Agricultural Resources assignment.
    Accessibility Statement does not exist.
    Privacy Policy

Properties of Soil: Agricultural
and Water Availability Impacts

Investigation
Manual

ENVIRONMENTAL SCIENCE

Made ADA compliant by
NetCentric Technologies using
the CommonLook® software

Key
Personal protective
equipment
(PPE)

goggles gloves apron
follow
link to
video

photograph
results and

submit

stopwatch
required

warning corrosion flammable toxic environment health hazard

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Overview
Earth’s soil plays a major role in the world’s agriculture and has a
substantial effect on water availability in a given area. In this inves-
tigation, students will analyze the natural porosity and particle size
of soil samples along with the chemical composition and profile of
different soil types.

Outcomes
• Examine the properties of soil and their effects on agriculture

and water availability.
• Describe and identify soil horizons based on their chemical and

physical composition.
• Distinguish between the particle sizes of three different types of

soil: sand, silt, and clay.
• Determine the porosity of different soil types.
• Analyze soil samples for a variety of nutrients to determine soil

fertility.

Time Requirements
Preparation …………………………………………………………….. 5 minutes
Activity 1: Particle Size Distribution and Determination of Soil
Texture
Day 1 …………………. 20 minutes, then let sit for 24 hours
Day 2 ……………………………………………………. 30 minutes
Activity 2: Porosity of Different Soil Types …………………. 60 minutes
Activity 3: pH Test Comparison of Soil Samples ………… 30 minutes
Activity 4: Nitrogen, Phosphorus, and Potash Test Comparisons of
Soil Samples
Day 1 …………………. 20 minutes, then let sit for 24 hours
Day 2 ……………………………………………………. 60 minutes

2 Carolina Distance Learning

Table of Contents

2 Overview
2 Outcomes
2 Time Requirements
3 Background
10 Materials
11 Safety
11 Preparation
12 Activity 1
13 Activity 2
14 Activity 3
16 Submission
16 Disposal and Cleanup
17 Lab Worksheet

Background
Soil Horizons and Chemical Composition
The type of dirt that makes up the dry
surfaces of the earth has numerous effects on
humans and the environment, and vice versa.
Humans can modify the suitability of some
areas for agriculture based on prior land use.
The properties of soil also determine water
availability in a given area. Areas that contain the
most suitable soil for farming are often limited.

Certain properties of soil determine whether
an area is suitable for human activity. When
considering the properties of soil, its texture,
shape, particle aggregation, and suitability for
growth come to mind. These properties all play
a major role in determining the capability of an
area to retain water and air, which are necessary
for several agricultural processes that are vital to
human life.

It is important to understand the profile and
chemical composition of soil to understand how
they affect agriculture and water availability. For
instance, some farmlands have been plowed
for hundreds of years yet the soil has remained
very fertile. However, in other areas with a similar
history, much of the soil has been adversely
affected (over one-third of the soil in the United
States is now deemed as destroyed). With years
of continuously turning over the soil to cultivate
crops, the damage accumulates and many areas
are left vulnerable to erosion, weathering, and
deterioration of nutrient and organic material.
Why then is there such great disparity in the way
certain soils flourish? It is because of the various
layers, or horizons, of the soil.

Soils differ greatly depending on the proportion
of each of these horizons (see Figure 1). If you

were to dig a hole or drive a corer (a special
drill that uses a hollow steel tube to remove a
cylindrical dirt sample) deep into the ground to
extract a sample of soil, a visible color difference
would be evident in the soil profile, or horizon
composition. The colors of the various horizons
differ based on the organic content and mineral
composition of each soil. Each horizon can
also vary in texture, which is determined by the
makeup of sand, silt, or clay.

As shown in Figure 1:

• The O-horizon is the most nutrient-rich
part of the soil profile, mainly because of its
abundance in organic matter. This layer is
often referred to as the humus layer and is
usually dark brown or black in color.

continued on next page

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Figure 1.

Background continued
• The A-horizon, also known as topsoil, is the

next layer down. This layer contains some
organic matter in addition to a mixture of
minerals. This horizon tends to be lighter black
to brown in color.

• Further down is the B-horizon, or the subsoil.
Much of the soil in this region has undergone
some degree of weathering and is composed
almost entirely of mineral material. Its high iron
and clay content usually imparts a reddish
color.

• The C-horizon is generally composed of
weathered rock fragments and material from
the layers above.

• The lowest region is known as the R-layer
(sometimes referred to as the D-horizon),
which mostly consists of unaltered bedrock
material.

It is important to note that all these layers are
not necessarily present in every soil profile and
the proportions of each layer can vary drastically
among various soil samples. Thus, with the
farmland example earlier, much of the fertile
soil may have had thicker O- and A-horizons,
making it more suitable for agriculture even after
many years, whereas the damaged soil may
have had much thinner top layers. The ages of
these soils may make a considerable difference
as well. Older soils tend to have almost all
horizons present, and younger soils tend to have
far fewer horizons.

Identifying Soil Types: Texture and Structure
In addition to distinguishing the chemical and
biological makeup of soil, it is also important
to understand the impact of soil on water
availability in a given area. Particle size is

one of the most important aspects of soil type
descriptions that helps to determine the holding
capacity of the soil as well as its ability to filter
water. The size of soil particles determines
the soil’s texture, which can be classified into
smaller subcategories (primary units) depending
on the mineral components of the soil. Texture is
determined by the ratio of sand, silt, and clay in
the soil sample (see Table 1).

Every soil sample will have different proportions
of these primary units. Based on these
proportions, each soil sample can be further
categorized and identified. Figure 2 shows a
soil analysis chart that illustrates the different
classes of soil based on their combinations of
sand, silt, and clay. Loam is a close-to-equal
mixture of these three primary units and can be
used to identify multiple soil types.

Determining particle size (based on these
subcategories of soil texture) is the first step
in soil characterization. The next step is
determining the structure of the soil, which
defines how the individual particles aggregate.

continued on next page

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PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Soil Type Particle Size

Sand Particles with a diameter greater
than 0.05 mm

Silt Particles with a diameter between
0.002 and 0.05 mm

Clay Particles with a diameter less than
0.002 mm

Table 1.

The soil structure affects how easily air, water,
and the roots of plants are able to move within
the soil. The arrangement of soil particle
aggregates can be broken down into peds, or
secondary units of the primary soil particles—
sand, silt, and clay.

Knowing the type of soil present by first
identifying the primary and secondary particle

continued on next page

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Figure 2.

types can help determine whether the soil is
suitable for agriculture. Soil permeability (ability
of water to flow through a soil) is directly related
to the particle size (texture) and the aggregation
of those particles (structure) (see Figure 3).
Rounded, granular peds are particularly suitable
for plant growth because their structure easily
permits penetration by air, water, and roots. Clay

Background continued
and loamy soils often have blocky peds that
are angular and somewhat irregular in shape
and permit the flow of air and water. In platy
peds, however, some passageways are blocked
because the soil particles are tightly packed.
A platy soil usually has high clay content and
often occurs in areas that are frequently flooded.
These classifications are not applicable to sand
because of its inability to form aggregates; thus,
instead of clumping, it falls apart.

The roots of plants require air and water. Just
as a plant can die from lack of water, it can also
die in waterlogged soil owing to a lack of air. Soil
must retain water and permit root penetration
to support plant life. However, certain particle

sizes and arrangements of particles allows
for permeability conditions that could be
detrimental to agriculture. Therefore, particle
size and arrangement need to be identified
to determine proper soil usage. Porosity is
defined as the amount of void space between
individual soil particles. With high porosity
between particles, a greater volume of water
can permeate but might also waterlog certain
systems. Porosity is another major property
of soil that has a significant effect on water
infiltration and soil fertility, or the ability of soil
to hold sufficient nutrients for plant growth. In
the following section, nutrient availability and
chemical composition—and their effects on
different soil types—are discussed.

Processes Affecting the Fertility of Soil
Determining the productivity of the soil in a given
area is crucial. The pH value, or the number
of hydrogen ions present in the soil, is a major
indicator of soil fertility. The pH scale ranges
from 0 to 14, with a value of 7 being neutral.
Anything less than 7 is acidic, and anything
more than 7 is considered basic. This scale is
logarithmic, so if a solution has a pH of 6, it has
ten times the number of hydrogen ions (or is
ten times more acidic) than a solution with a pH
of 7 possesses. There are wide ranges of pH
for a variety of soils; for example, quartz-rich
sandstone is rather acidic, whereas limestone
tends to be basic.

Rainwater, which has a pH of approximately
5.5, has a significant impact on soil pH. The
low pH of rainwater is caused by the mixing of
water with carbon dioxide in the atmosphere.
Carbonic acid is formed when the precipitation

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PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Figure 3.

Platy

Blocky

Granular

Columnar

makes contact with the earth’s surface. As this
rainwater flows into and along soil surfaces,
it transmits many nutrients into the depths of
the soil. Iron, along with other minerals such as
calcium and magnesium, tends to flow through
the higher horizons, which are usually flourishing
with life, and continues into the lower horizons
that tend to be lacking in nutrients.

Besides pH, decomposition is another
important factor in determining the health of
soil. Organisms such as bacteria and fungi
decompose (break down) organic matter that
plants and animals produce at the surface and
deposit into the soil, allowing for the survival
of organisms deeper in the soil. The rate of
decomposition can be increased by worms and

other organisms living near the surface. These
organisms break down detritus (debris and
waste) into smaller bits that sink farther into the
soil, feeding the bacteria and fungi.

Nutrients are essential for plant growth. One
major issue regarding the health of certain soil
types in some areas is the inability of the soil to
retain sufficient nutrients. Adding fertilizers and
pesticides helps replenish crops and soil, but an
excess of these nutrients can also exert negative
effects. Macronutrients are nutrients needed at
high concentrations by all living things. Nitrogen,
potassium, phosphate, and magnesium are
examples of these nutrients necessary for plant
growth. Micronutrients—such as the metals
zinc, iron, and copper—are those needed in
smaller quantities.

Fertilizers are useful to replace macronutrients
lost from the soil. Many fertilizers,
such as manure, are either purely
or mostly organic matter; however,
numerous synthetic fertilizers have
also been developed. Nitrogen,
phosphorous, and potassium are
commonly regarded as the limiting
nutrients in crop production and are
therefore typically added to soils in
specific amounts via fertilizers.

Nitrogen is a special case; plants
require nitrogen in the form
of ammonium or nitrate, and
atmospheric nitrogen can only
be converted synthetically, or by
soil-dwelling microbes, as part of
the nitrogen cycle (see Figure 4).

continued on next page

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Figure 4.

Background continued
Additional ways in which nitrogen can enter the
soil include via the death and decomposition
of plants and by the production of nitrogenous
waste from plants being eaten by animals.
Nitrogen is vital for plant growth; it is a very
important structural component of chlorophyll,
the compound used by plants in photosynthesis
to produce oxygen and sugars. Nitrogen is
also a major component of amino acids, which
are the building blocks of proteins. Since it is
not retained by soil, excess nitrogen can leach
onto the surface or into groundwater, causing
algal blooms and a loss of oxygen. Although
nitrogen is an essential element, because it is
not retained by the soil, farmers frequently need
to reapply fertilizers containing nitrates, which in
turn can lead to environmental challenges.

Phosphorus is usually present in the form
of phosphates in the soil. Phosphate is
an important component of adenosine
triphosphate/adenosine diphosphate (ATP/ADP)
in plants and is therefore necessary for energy
transport and storage. Phosphates, along with
pentose sugars, make up the backbone of DNA
and RNA. Phosphorus availability frequently
limits plant growth and flowering; therefore, the
introduction of phosphates into soil can lead

to rapid plant growth. This element also plays
a major role in keeping the root systems of
plants strong and thriving. However, like excess
nitrates, too much phosphorus can lead to algal
blooms, which can harm aquatic ecosystems
(see details of the phosphorus cycle in Figure 5).

The last main nutrient in fertilizer is known
as potash. It is a mixture of various salts that
contain soluble potassium, which is vital for
the development of many flowers and fruits.
Potassium is required for the activation of
numerous enzymes and for the regulation of pH
as well. It also controls the opening and closing
of the stomata (pores in the leaves), which
affects photosynthesis, water and gas transport,
and temperature regulation.

In this investigation, you will conduct
experiments to determine the texture and
structure of soil samples as well as the ability of
water to permeate each sample. You will also
perform chemical tests to determine the fertility
of two soil samples.

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PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

continued on next page

www.carolina.com/distancelearning 9

Figure 5.

10 Carolina Distance Learning

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Materials
Included in the materials kit:

rapitest® Soil
Tester kit

Bag of clay,
½ c

Cheesecloth

3 Rubber
bands

6 Twist ties

Needed but not supplied:
• Sheet of white paper
• 2 Soil samples
• Distilled water
• Tap water
• Liquid hand soap
• Tool for digging soil

(trowel, large spoon,
etc.)

• Scissors
• Stopwatch (or cell

phone with a timer)
• Camera (or cell

phone capable of
taking photographs)

• 2 jars or cans,16 oz
or less

3 Plastic tubes

Graduated
cylinder, 10 mL

Graduated
cylinder, 100 mL

Plastic cup

Permanent
marker

Ruler

Test tube rack3 Test tubes

2 Pipets

Needed from the equipment kit:

Reorder Information: Replacement supplies
for the Properties of Soil: Agricultural and
Water Availability Impacts investigation can
be ordered from Carolina Biological Supply
Company, item number 580822.

Call: 800.334.5551 to order.

Needed from the
Groundwater and Surface
Water Interactions
investigation materials kit:
• 2 small handfuls of sand

from the large bag of sand

Safety
Wear your safety
goggles, gloves, and
lab apron for the duration of this investigation.

Read all the instructions for these laboratory
activities before beginning. Follow the instruc-
tions closely, and observe established laboratory
safety practices, including the use of appropriate
personal protective equipment (PPE).

Avoid contact with skin, eyes, and
mouth when working with rapitest®
Soil Tester capsules. Wear PPE at all

times when using these capsules. Wash your
hands immediately following the use of these
capsules.

Do not eat, drink, or chew gum while performing
these activities. Wash your hands with soap and
water before and after performing each activity.
Clean the work area with soap and water after
completing the investigation. Keep pets and
children away from lab materials and equipment.

Preparation
1. Read through the activities.
2. Obtain all materials.
3. Identify a location where you can easily

collect a small amount of soil out of the
ground (e.g., at the edge of your yard or at a
nearby park).

4. Using your digging tool, collect a few
handfuls of soil from about 3 inches below
the surface and place it in a plastic cup from
the equipment kit. (There should be enough
to fill the cup approximately halfway.) This
sample will be known as “Soil Sample A” and
will be used in all the activities. Before using
the sample, remove excess grasses, roots,
and other plant materials and break up any
large clumps.

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ACTIVITY

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12 Carolina Distance Learning

ACTIVITY 1
Particle Size Distribution and
Determination of Soil Texture

Day 1
1. Take three test tubes from the equipment

kit and label them “Sand,” “Clay,” and “Soil
Sample A” (one for each sample).

2. Fill each vial halfway with its designated soil
sample. For each test tube, add tap water to
about 1 cm below the top. Then add one drop
of liquid hand soap to each sample (this helps
settle the particles).

3. With gloved hands for each test tube,
place your thumb over the opening.
Shake each test tube for 30 seconds. Allow
the samples to settle overnight in the test
tube rack. Place a piece of paper over
the top of the three test tubes to prevent
contamination of the samples.

4. Hypothesize what percentages of sand, silt,
and clay you expect to find in “Soil Sample A.”
Remember: your percentages must add
up to 100%. Record your hypothesis in the
“Hypotheses” section of the Lab Worksheet.

Day 2
1. Place a sheet of white paper behind

the test tubes containing the settled
soil samples, and observe the layers that
have formed in each. Take a photograph
of the three samples with the paper behind
them. Include in your photograph a strip of
paper with your name and the date clearly
written on it. You will be uploading this
photograph to your lab report.

How to Determine Soil Composition
https://bcove.video/2N8VShc

2. Using the “Sand” and “Clay” samples as
controls, identify the layer types in “Soil
Sample A.” You may use a marker to label
each layer. See Figure 6 for guidance.

3. Use a ruler to measure the thickness (in
centimeters) of the sand, silt, and clay layers
in “Soil Sample A.” The silt layer is the layer
formed between the clay and sand layers,
owing to its particle size that is larger than
that of clay but smaller than that of sand (see
Figure 6). Record these values in Data Table 1
of the “Observations/Data Tables” section of
the Lab Worksheet.

All layers may not be visible or may vary
substantially in depth in “Soil Sample A.”

4. Measure the total depth of the soil. Be careful
to exclude the humus layer containing floating
dirt and grasses at the top of the sample (see
Figure 6). Record the total depth in Data Table
1 of the “Observations/Data Tables” section
of the Lab Worksheet.

Figure 6.

A

5. Calculate the particle size distribution of “Soil
Sample A” by dividing the depth of each
layer by the total depth of the soil, and then
multiplying that value by 100. Record the
percentages of the primary particles clay, silt,
and sand in “Soil Sample A” in Data Table 1
of the “Observations/Data Tables” section of
the Lab Worksheet.

6. Use the soil analysis chart (see Figure 2) to
determine the soil texture of “Soil Sample
A,” and record this in Data Table 1 of the
“Observations/Data Tables” section of the
Lab Worksheet.

How to Determine Soil Texture
https://bcove.video/305wPQ6

Note: In Figure 2, each corner of the triangle
represents 100% of one of the three types of
soil: silt, sand, and clay. Locate these points.
Loam is found in the center of the triangle.
Following the arrows on the sides of the tri-
angle, start by pointing to the percentage
of your soil sample that is composed of silt
(from Table 1) on the right edge of the triangle.
With your other hand, point to the percentage
composed of sand along the bottom edge.
Following the corresponding diagonal lines,
move your fingers toward each other until the
lines intersect. (If you have found the correct
intersecting lines, the percentage of clay of
your sample should line up horizontally on the
left edge from the point at which your fingers
meet). This point of intersection represents
the class of soil texture; if the point falls on a
boundary between two types, choose the one
that occupies a larger area. Also, if the per-

centage of either silt or sand is less than 10%
for your specific “Soil Sample A,” start your
fingers on clay and the existing primary parti-
cle and follow the same process.

ACTIVITY 2

Porosity of Different Soil Types
1. Ensure the remaining “Sand,” “Clay,” and

“Soil Sample A” are ready for use. In this
activity, you will be determining the porosities
(relative empty space) of three different
samples. Before you begin, hypothesize
which sample you think will have the highest
porosity and which one will have the lowest
porosity and explain why. Record your
hypothesis in the “Hypotheses” section of the
Lab Worksheet.

2. Cut two 3-cm squares from the cheesecloth.
3. Secure these two pieces

of cheesecloth over one
end of a plastic tube with a
rubber band (see Figure 7).

4. Make a mark on the tube
4 cm up from the end
covered by cheesecloth.

5. Pour one of the three
samples onto a paper
towel, and make sure any
lumps or rocks are crushed
or removed. Fill the tube
up to the 4-cm mark with
the particular sample (see
Figure 7). Use twist ties to
suspend the tube in the
100-mL graduated cylinder
(see Figure 7).

www.carolina.com/distancelearning 13

Figure 7.

continued on next page

A

ACTIVITY

14 Carolina Distance Learning

6. Start a timer as you pour 10 mL of tap
water from the 10-mL graduated
cylinder into the plastic tube in the setup.

7. Record the time (in seconds) taken for the
first drop of water to emerge from the column,
and record this data in Data Table 2 of the
“Observations/Data Tables” section of the
Lab Worksheet. For some samples, this
could happen very quickly (even as you are
pouring), so keep a close eye on the sample
as you are pouring.

8. Repeat Steps 2–7 with the two remaining
samples (using new materials for each
sample).

ACTIVITY 3
pH Test Comparison of Soil
Samples

For Activities 3 and 4, use the soil from the
initial collection in the “Preparation” section
(“Soil Sample A”). For another soil sample
(this will be called “Soil Sample B”), collect
a sample of your choice—for example,
this can be commercial potting soil, soil
from a different outdoor location, or any
remaining clay from this lab. Avoid using
any remaining sand since it carries little
nutritional value due to its large pore
space.

Ideally, the best option would be to find
another soil sample from a different outdoor
location with contrasting properties. For
example, if “Soil Sample A” was from a very
dry area without plants, try to find a very
moist soil sample that is covered with grass

ACTIVITY 2 continued

A

for “Soil Sample B.” You can also select a
deeper soil sample for comparison with the
surface-based “Soil Sample A.”

1. Propose a hypothesis concerning which
of the two samples will be the more
acidic of the two and which one the more
basic. Explain your reasoning. Record
the hypothesis and reasoning in the
“Hypotheses” section of the Lab Worksheet.

2. Open the rapitest® Soil Tester kit.
3. Wearing PPE, remove the capsules from

one of the green-capped vials (the pH test
capsules).

4. Fill the vial with “Soil Sample A” up to the
first line.

5. Carefully open one of the green capsules and
pour the powder into the vial. (Do this over
the vial to prevent any spillage.)

6. Add distilled water up to the fourth line.
7. Cap the vial, and shake it thoroughly

(about 20 seconds).
8. Allow the soil to settle for approximately

one minute.
9. Compare the color of your sample to those

on the pH color chart on the back of the
rapitest® Soil Tester kit instructions (the
“Plant Food Color Chart”) to determine the
pH of the soil sample. Record this data in
Data Table 3 of the “Observations/Data
Tables” section of the Lab Worksheet.

10. Take a photograph of your vial held
up next to the “Plant Food Color
Chart.” Include in your photograph a strip of
paper with your name and the date clearly

continued on next page

www.carolina.com/distancelearning 15

Day 2
1. Wearing PPE, remove the caps from the

purple, blue, and orange vials from the
rapitest® Soil Tester kit and remove their
capsules.

2. Using a pipet from the equipment kit, fill each
vial up to the fourth line with the supernatant
(liquid above the soil) from the “Soil Sample
A” mixture made on Day 1.

3. Carefully separate the capsules, and pour the
powder into the corresponding-colored vials.
Make sure the colors of the capsules match
the respective vials. (Perform this step over
the vial to prevent spillage of the powder).

4. Cap the vial, and shake it thoroughly (for
about 20 seconds).

5. Allow color to develop for 10 minutes.
6. Use the “Plant Food Color Chart” on the back

of the rapitest® Soil Tester kit instructions
to determine the nutrient content of the soil
sample. Record this data in Data Table 4 of
the “Observations/Data Tables” section of the
Lab Worksheet.

7. Take a photograph of your vial held up
next to the “Plant Food Color Chart.”
Include in your photograph a strip of paper
with your name and the date clearly written
on it. You will be uploading this photograph to
your lab report.

8. Rinse the vials, and repeat Steps 1–7 with the
other soil mixture (“Soil Sample B”).

A

written on it. You will be uploading this
photograph to your lab report.

11. Dump out the soil mixture into the
household trash.

12. Rinse the vial, and repeat Steps 2–11 with
the other soil sample you chose (“Soil
Sample B”).

ACTIVITY 4
Nitrogen, Phosphorus, and Potash
Test Comparisons of Soil Samples

Consider your two soil samples, particularly in
terms of where you obtained them and their
appearance. Based on the characteristics
and what they have contained so far,
hypothesize which will have a higher level of
nutrients (nitrogen, phosphorus, and potash)
and which will have a lower level. Explain why,
and record your hypothesis in the “Hypotheses”
section of the Lab Worksheet.

Day 1
1. Fill a clean jar or can with 1 part

“Soil Sample A” and 5 parts water.
Thoroughly swirl the soil and water together
for 1 minute; then allow the mixture to settle
(approximately 24 hours).

2. Repeat Step 1 with “Soil Sample B” and a
different jar or can.

ACTIVITY

16 Carolina Distance Learning

Submission
Using the Lab Report Template provided,
submit your completed report to Waypoint
for grading. It is not necessary to turn in the
Lab Worksheet.

Disposal and Cleanup
1. Rinse and dry the lab equipment from the

equipment kit, and return the materials to
your equipment kit.

2. Discard the soil samples and any other
materials from the materials kit in the
household trash. The 10 mL graduated
cylinder and plastic tubes may be recyclable.

3. Sanitize the work space, and wash your
hands thoroughly.

www.carolina.com/distancelearning 17

ACTIVITY

Lab Worksheet
Hypotheses

Activity 1.

Activity 2.

Activity 3.

Activity 4.

continued on next page

ACTIVITY

18 Carolina Distance Learning

Data Table 3.

pH Comparison of Soil Samples

Soil Sample A Soil Sample B
(Location Description: _____________________________)

pH

Data Table 4.

Nitrogen, Phosphorus, and Potash Comparison in Soil Samples

Nitrogen Phosphorus Potash

Soil Sample A

Soil Sample B

Observations/Data Tables

Data Table 1.

Particle Size Distribution and Soil Type

Depth of
Clay Layer

(cm)

Depth of
Silt Layer

(cm)

Depth of
Sand Layer

(cm)

Total
Depth
(cm)

%
Clay

%
Silt

%
Sand

Soil
Texture

Soil
Sample A

Data Table 2.

Determination of Soil Porosity

Time Taken for First Drop to Emerge from Column (s)

Sand Sample

Clay Sample

Soil Sample A

NOTES

www.carolina.com/distancelearning 19

ENVIRONMENTAL SCIENCE
Properties of Soil: Agricultural and Water Availability Impacts

Investigation Manual

www.carolina.com/distancelearning
866.332.4478

Carolina Biological Supply Company
www.carolina.com • 800.334.5551
©2019 Carolina Biological Supply Company

CB781641908 ASH_V2.2

  • Properties of Soil: Agricultural and Water Availability Impacts
    • Table of Contents
    • Overview
    • Outcomes
    • Time Requirements
    • Key
    • Background
      • Soil Horizons and Chemical Composition
      • Identifying Soil Types: Texture and Structure
      • Processes Affecting the Fertility of Soil
    • Materials
      • Included in the materials kit:
      • Needed from the equipment kit:
      • Needed but not supplied:
    • Safety
    • Preparation
    • ACTIVITY 1
      • A Particle Size Distribution and Determination of Soil Texture
        • Day 1
        • Day 2
    • ACTIVITY 2
      • A Porosity of Different Soil Types
    • ACTIVITY 3
      • A pH Test Comparison of Soil Samples
    • ACTIVITY 4
      • A Nitrogen, Phosphorus, and Potash Test Comparisons of Soil Samples
        • Day 1
        • Day 2
    • Submission
    • Disposal and Cleanup
    • Lab Worksheet
      • Hypotheses
      • Observations/Data Tables
    • NOTES

Properties of Soil: Agricultural
and Water Availability Impacts

Investigation
Manual

ENVIRONMENTAL SCIENCE

Made ADA compliant by
NetCentric Technologies using
the CommonLook® software

Key
Personal protective
equipment
(PPE)

goggles gloves apron
follow
link to
video

photograph
results and

submit

stopwatch
required

warning corrosion flammable toxic environment health hazard

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Overview
Earth’s soil plays a major role in the world’s agriculture and has a
substantial effect on water availability in a given area. In this inves-
tigation, students will analyze the natural porosity and particle size
of soil samples along with the chemical composition and profile of
different soil types.

Outcomes
• Examine the properties of soil and their effects on agriculture

and water availability.
• Describe and identify soil horizons based on their chemical and

physical composition.
• Distinguish between the particle sizes of three different types of

soil: sand, silt, and clay.
• Determine the porosity of different soil types.
• Analyze soil samples for a variety of nutrients to determine soil

fertility.

Time Requirements
Preparation …………………………………………………………….. 5 minutes
Activity 1: Particle Size Distribution and Determination of Soil
Texture
Day 1 …………………. 20 minutes, then let sit for 24 hours
Day 2 ……………………………………………………. 30 minutes
Activity 2: Porosity of Different Soil Types …………………. 60 minutes
Activity 3: pH Test Comparison of Soil Samples ………… 30 minutes
Activity 4: Nitrogen, Phosphorus, and Potash Test Comparisons of
Soil Samples
Day 1 …………………. 20 minutes, then let sit for 24 hours
Day 2 ……………………………………………………. 60 minutes

2 Carolina Distance Learning

Table of Contents

2 Overview
2 Outcomes
2 Time Requirements
3 Background
10 Materials
11 Safety
11 Preparation
12 Activity 1
13 Activity 2
14 Activity 3
16 Submission
16 Disposal and Cleanup
17 Lab Worksheet

Background
Soil Horizons and Chemical Composition
The type of dirt that makes up the dry
surfaces of the earth has numerous effects on
humans and the environment, and vice versa.
Humans can modify the suitability of some
areas for agriculture based on prior land use.
The properties of soil also determine water
availability in a given area. Areas that contain the
most suitable soil for farming are often limited.

Certain properties of soil determine whether
an area is suitable for human activity. When
considering the properties of soil, its texture,
shape, particle aggregation, and suitability for
growth come to mind. These properties all play
a major role in determining the capability of an
area to retain water and air, which are necessary
for several agricultural processes that are vital to
human life.

It is important to understand the profile and
chemical composition of soil to understand how
they affect agriculture and water availability. For
instance, some farmlands have been plowed
for hundreds of years yet the soil has remained
very fertile. However, in other areas with a similar
history, much of the soil has been adversely
affected (over one-third of the soil in the United
States is now deemed as destroyed). With years
of continuously turning over the soil to cultivate
crops, the damage accumulates and many areas
are left vulnerable to erosion, weathering, and
deterioration of nutrient and organic material.
Why then is there such great disparity in the way
certain soils flourish? It is because of the various
layers, or horizons, of the soil.

Soils differ greatly depending on the proportion
of each of these horizons (see Figure 1). If you

were to dig a hole or drive a corer (a special
drill that uses a hollow steel tube to remove a
cylindrical dirt sample) deep into the ground to
extract a sample of soil, a visible color difference
would be evident in the soil profile, or horizon
composition. The colors of the various horizons
differ based on the organic content and mineral
composition of each soil. Each horizon can
also vary in texture, which is determined by the
makeup of sand, silt, or clay.

As shown in Figure 1:

• The O-horizon is the most nutrient-rich
part of the soil profile, mainly because of its
abundance in organic matter. This layer is
often referred to as the humus layer and is
usually dark brown or black in color.

continued on next page

www.carolina.com/distancelearning 3

Figure 1.

Background continued
• The A-horizon, also known as topsoil, is the

next layer down. This layer contains some
organic matter in addition to a mixture of
minerals. This horizon tends to be lighter black
to brown in color.

• Further down is the B-horizon, or the subsoil.
Much of the soil in this region has undergone
some degree of weathering and is composed
almost entirely of mineral material. Its high iron
and clay content usually imparts a reddish
color.

• The C-horizon is generally composed of
weathered rock fragments and material from
the layers above.

• The lowest region is known as the R-layer
(sometimes referred to as the D-horizon),
which mostly consists of unaltered bedrock
material.

It is important to note that all these layers are
not necessarily present in every soil profile and
the proportions of each layer can vary drastically
among various soil samples. Thus, with the
farmland example earlier, much of the fertile
soil may have had thicker O- and A-horizons,
making it more suitable for agriculture even after
many years, whereas the damaged soil may
have had much thinner top layers. The ages of
these soils may make a considerable difference
as well. Older soils tend to have almost all
horizons present, and younger soils tend to have
far fewer horizons.

Identifying Soil Types: Texture and Structure
In addition to distinguishing the chemical and
biological makeup of soil, it is also important
to understand the impact of soil on water
availability in a given area. Particle size is

one of the most important aspects of soil type
descriptions that helps to determine the holding
capacity of the soil as well as its ability to filter
water. The size of soil particles determines
the soil’s texture, which can be classified into
smaller subcategories (primary units) depending
on the mineral components of the soil. Texture is
determined by the ratio of sand, silt, and clay in
the soil sample (see Table 1).

Every soil sample will have different proportions
of these primary units. Based on these
proportions, each soil sample can be further
categorized and identified. Figure 2 shows a
soil analysis chart that illustrates the different
classes of soil based on their combinations of
sand, silt, and clay. Loam is a close-to-equal
mixture of these three primary units and can be
used to identify multiple soil types.

Determining particle size (based on these
subcategories of soil texture) is the first step
in soil characterization. The next step is
determining the structure of the soil, which
defines how the individual particles aggregate.

continued on next page

4 Carolina Distance Learning

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Soil Type Particle Size

Sand Particles with a diameter greater
than 0.05 mm

Silt Particles with a diameter between
0.002 and 0.05 mm

Clay Particles with a diameter less than
0.002 mm

Table 1.

The soil structure affects how easily air, water,
and the roots of plants are able to move within
the soil. The arrangement of soil particle
aggregates can be broken down into peds, or
secondary units of the primary soil particles—
sand, silt, and clay.

Knowing the type of soil present by first
identifying the primary and secondary particle

continued on next page

www.carolina.com/distancelearning 5

Figure 2.

types can help determine whether the soil is
suitable for agriculture. Soil permeability (ability
of water to flow through a soil) is directly related
to the particle size (texture) and the aggregation
of those particles (structure) (see Figure 3).
Rounded, granular peds are particularly suitable
for plant growth because their structure easily
permits penetration by air, water, and roots. Clay

Background continued
and loamy soils often have blocky peds that
are angular and somewhat irregular in shape
and permit the flow of air and water. In platy
peds, however, some passageways are blocked
because the soil particles are tightly packed.
A platy soil usually has high clay content and
often occurs in areas that are frequently flooded.
These classifications are not applicable to sand
because of its inability to form aggregates; thus,
instead of clumping, it falls apart.

The roots of plants require air and water. Just
as a plant can die from lack of water, it can also
die in waterlogged soil owing to a lack of air. Soil
must retain water and permit root penetration
to support plant life. However, certain particle

sizes and arrangements of particles allows
for permeability conditions that could be
detrimental to agriculture. Therefore, particle
size and arrangement need to be identified
to determine proper soil usage. Porosity is
defined as the amount of void space between
individual soil particles. With high porosity
between particles, a greater volume of water
can permeate but might also waterlog certain
systems. Porosity is another major property
of soil that has a significant effect on water
infiltration and soil fertility, or the ability of soil
to hold sufficient nutrients for plant growth. In
the following section, nutrient availability and
chemical composition—and their effects on
different soil types—are discussed.

Processes Affecting the Fertility of Soil
Determining the productivity of the soil in a given
area is crucial. The pH value, or the number
of hydrogen ions present in the soil, is a major
indicator of soil fertility. The pH scale ranges
from 0 to 14, with a value of 7 being neutral.
Anything less than 7 is acidic, and anything
more than 7 is considered basic. This scale is
logarithmic, so if a solution has a pH of 6, it has
ten times the number of hydrogen ions (or is
ten times more acidic) than a solution with a pH
of 7 possesses. There are wide ranges of pH
for a variety of soils; for example, quartz-rich
sandstone is rather acidic, whereas limestone
tends to be basic.

Rainwater, which has a pH of approximately
5.5, has a significant impact on soil pH. The
low pH of rainwater is caused by the mixing of
water with carbon dioxide in the atmosphere.
Carbonic acid is formed when the precipitation

continued on next page

6 Carolina Distance Learning

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Figure 3.

Platy

Blocky

Granular

Columnar

makes contact with the earth’s surface. As this
rainwater flows into and along soil surfaces,
it transmits many nutrients into the depths of
the soil. Iron, along with other minerals such as
calcium and magnesium, tends to flow through
the higher horizons, which are usually flourishing
with life, and continues into the lower horizons
that tend to be lacking in nutrients.

Besides pH, decomposition is another
important factor in determining the health of
soil. Organisms such as bacteria and fungi
decompose (break down) organic matter that
plants and animals produce at the surface and
deposit into the soil, allowing for the survival
of organisms deeper in the soil. The rate of
decomposition can be increased by worms and

other organisms living near the surface. These
organisms break down detritus (debris and
waste) into smaller bits that sink farther into the
soil, feeding the bacteria and fungi.

Nutrients are essential for plant growth. One
major issue regarding the health of certain soil
types in some areas is the inability of the soil to
retain sufficient nutrients. Adding fertilizers and
pesticides helps replenish crops and soil, but an
excess of these nutrients can also exert negative
effects. Macronutrients are nutrients needed at
high concentrations by all living things. Nitrogen,
potassium, phosphate, and magnesium are
examples of these nutrients necessary for plant
growth. Micronutrients—such as the metals
zinc, iron, and copper—are those needed in
smaller quantities.

Fertilizers are useful to replace macronutrients
lost from the soil. Many fertilizers,
such as manure, are either purely
or mostly organic matter; however,
numerous synthetic fertilizers have
also been developed. Nitrogen,
phosphorous, and potassium are
commonly regarded as the limiting
nutrients in crop production and are
therefore typically added to soils in
specific amounts via fertilizers.

Nitrogen is a special case; plants
require nitrogen in the form
of ammonium or nitrate, and
atmospheric nitrogen can only
be converted synthetically, or by
soil-dwelling microbes, as part of
the nitrogen cycle (see Figure 4).

continued on next page

www.carolina.com/distancelearning 7

Figure 4.

Background continued
Additional ways in which nitrogen can enter the
soil include via the death and decomposition
of plants and by the production of nitrogenous
waste from plants being eaten by animals.
Nitrogen is vital for plant growth; it is a very
important structural component of chlorophyll,
the compound used by plants in photosynthesis
to produce oxygen and sugars. Nitrogen is
also a major component of amino acids, which
are the building blocks of proteins. Since it is
not retained by soil, excess nitrogen can leach
onto the surface or into groundwater, causing
algal blooms and a loss of oxygen. Although
nitrogen is an essential element, because it is
not retained by the soil, farmers frequently need
to reapply fertilizers containing nitrates, which in
turn can lead to environmental challenges.

Phosphorus is usually present in the form
of phosphates in the soil. Phosphate is
an important component of adenosine
triphosphate/adenosine diphosphate (ATP/ADP)
in plants and is therefore necessary for energy
transport and storage. Phosphates, along with
pentose sugars, make up the backbone of DNA
and RNA. Phosphorus availability frequently
limits plant growth and flowering; therefore, the
introduction of phosphates into soil can lead

to rapid plant growth. This element also plays
a major role in keeping the root systems of
plants strong and thriving. However, like excess
nitrates, too much phosphorus can lead to algal
blooms, which can harm aquatic ecosystems
(see details of the phosphorus cycle in Figure 5).

The last main nutrient in fertilizer is known
as potash. It is a mixture of various salts that
contain soluble potassium, which is vital for
the development of many flowers and fruits.
Potassium is required for the activation of
numerous enzymes and for the regulation of pH
as well. It also controls the opening and closing
of the stomata (pores in the leaves), which
affects photosynthesis, water and gas transport,
and temperature regulation.

In this investigation, you will conduct
experiments to determine the texture and
structure of soil samples as well as the ability of
water to permeate each sample. You will also
perform chemical tests to determine the fertility
of two soil samples.

8 Carolina Distance Learning

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

continued on next page

www.carolina.com/distancelearning 9

Figure 5.

10 Carolina Distance Learning

PROPERTIES OF SOIL: AGRICULTURAL AND WATER
AVAILABILITY IMPACTS

Materials
Included in the materials kit:

rapitest® Soil
Tester kit

Bag of clay,
½ c

Cheesecloth

3 Rubber
bands

6 Twist ties

Needed but not supplied:
• Sheet of white paper
• 2 Soil samples
• Distilled water
• Tap water
• Liquid hand soap
• Tool for digging soil

(trowel, large spoon,
etc.)

• Scissors
• Stopwatch (or cell

phone with a timer)
• Camera (or cell

phone capable of
taking photographs)

• 2 jars or cans,16 oz
or less

3 Plastic tubes

Graduated
cylinder, 10 mL

Graduated
cylinder, 100 mL

Plastic cup

Permanent
marker

Ruler

Test tube rack3 Test tubes

2 Pipets

Needed from the equipment kit:

Reorder Information: Replacement supplies
for the Properties of Soil: Agricultural and
Water Availability Impacts investigation can
be ordered from Carolina Biological Supply
Company, item number 580822.

Call: 800.334.5551 to order.

Needed from the
Groundwater and Surface
Water Interactions
investigation materials kit:
• 2 small handfuls of sand

from the large bag of sand

Safety
Wear your safety
goggles, gloves, and
lab apron for the duration of this investigation.

Read all the instructions for these laboratory
activities before beginning. Follow the instruc-
tions closely, and observe established laboratory
safety practices, including the use of appropriate
personal protective equipment (PPE).

Avoid contact with skin, eyes, and
mouth when working with rapitest®
Soil Tester capsules. Wear PPE at all

times when using these capsules. Wash your
hands immediately following the use of these
capsules.

Do not eat, drink, or chew gum while performing
these activities. Wash your hands with soap and
water before and after performing each activity.
Clean the work area with soap and water after
completing the investigation. Keep pets and
children away from lab materials and equipment.

Preparation
1. Read through the activities.
2. Obtain all materials.
3. Identify a location where you can easily

collect a small amount of soil out of the
ground (e.g., at the edge of your yard or at a
nearby park).

4. Using your digging tool, collect a few
handfuls of soil from about 3 inches below
the surface and place it in a plastic cup from
the equipment kit. (There should be enough
to fill the cup approximately halfway.) This
sample will be known as “Soil Sample A” and
will be used in all the activities. Before using
the sample, remove excess grasses, roots,
and other plant materials and break up any
large clumps.

www.carolina.com/distancelearning 11

ACTIVITY

continued on next page

12 Carolina Distance Learning

ACTIVITY 1
Particle Size Distribution and
Determination of Soil Texture

Day 1
1. Take three test tubes from the equipment

kit and label them “Sand,” “Clay,” and “Soil
Sample A” (one for each sample).

2. Fill each vial halfway with its designated soil
sample. For each test tube, add tap water to
about 1 cm below the top. Then add one drop
of liquid hand soap to each sample (this helps
settle the particles).

3. With gloved hands for each test tube,
place your thumb over the opening.
Shake each test tube for 30 seconds. Allow
the samples to settle overnight in the test
tube rack. Place a piece of paper over
the top of the three test tubes to prevent
contamination of the samples.

4. Hypothesize what percentages of sand, silt,
and clay you expect to find in “Soil Sample A.”
Remember: your percentages must add
up to 100%. Record your hypothesis in the
“Hypotheses” section of the Lab Worksheet.

Day 2
1. Place a sheet of white paper behind

the test tubes containing the settled
soil samples, and observe the layers that
have formed in each. Take a photograph
of the three samples with the paper behind
them. Include in your photograph a strip of
paper with your name and the date clearly
written on it. You will be uploading this
photograph to your lab report.

How to Determine Soil Composition
https://bcove.video/2N8VShc

2. Using the “Sand” and “Clay” samples as
controls, identify the layer types in “Soil
Sample A.” You may use a marker to label
each layer. See Figure 6 for guidance.

3. Use a ruler to measure the thickness (in
centimeters) of the sand, silt, and clay layers
in “Soil Sample A.” The silt layer is the layer
formed between the clay and sand layers,
owing to its particle size that is larger than
that of clay but smaller than that of sand (see
Figure 6). Record these values in Data Table 1
of the “Observations/Data Tables” section of
the Lab Worksheet.

All layers may not be visible or may vary
substantially in depth in “Soil Sample A.”

4. Measure the total depth of the soil. Be careful
to exclude the humus layer containing floating
dirt and grasses at the top of the sample (see
Figure 6). Record the total depth in Data Table
1 of the “Observations/Data Tables” section
of the Lab Worksheet.

Figure 6.

A

5. Calculate the particle size distribution of “Soil
Sample A” by dividing the depth of each
layer by the total depth of the soil, and then
multiplying that value by 100. Record the
percentages of the primary particles clay, silt,
and sand in “Soil Sample A” in Data Table 1
of the “Observations/Data Tables” section of
the Lab Worksheet.

6. Use the soil analysis chart (see Figure 2) to
determine the soil texture of “Soil Sample
A,” and record this in Data Table 1 of the
“Observations/Data Tables” section of the
Lab Worksheet.

How to Determine Soil Texture
https://bcove.video/305wPQ6

Note: In Figure 2, each corner of the triangle
represents 100% of one of the three types of
soil: silt, sand, and clay. Locate these points.
Loam is found in the center of the triangle.
Following the arrows on the sides of the tri-
angle, start by pointing to the percentage
of your soil sample that is composed of silt
(from Table 1) on the right edge of the triangle.
With your other hand, point to the percentage
composed of sand along the bottom edge.
Following the corresponding diagonal lines,
move your fingers toward each other until the
lines intersect. (If you have found the correct
intersecting lines, the percentage of clay of
your sample should line up horizontally on the
left edge from the point at which your fingers
meet). This point of intersection represents
the class of soil texture; if the point falls on a
boundary between two types, choose the one
that occupies a larger area. Also, if the per-

centage of either silt or sand is less than 10%
for your specific “Soil Sample A,” start your
fingers on clay and the existing primary parti-
cle and follow the same process.

ACTIVITY 2

Porosity of Different Soil Types
1. Ensure the remaining “Sand,” “Clay,” and

“Soil Sample A” are ready for use. In this
activity, you will be determining the porosities
(relative empty space) of three different
samples. Before you begin, hypothesize
which sample you think will have the highest
porosity and which one will have the lowest
porosity and explain why. Record your
hypothesis in the “Hypotheses” section of the
Lab Worksheet.

2. Cut two 3-cm squares from the cheesecloth.
3. Secure these two pieces

of cheesecloth over one
end of a plastic tube with a
rubber band (see Figure 7).

4. Make a mark on the tube
4 cm up from the end
covered by cheesecloth.

5. Pour one of the three
samples onto a paper
towel, and make sure any
lumps or rocks are crushed
or removed. Fill the tube
up to the 4-cm mark with
the particular sample (see
Figure 7). Use twist ties to
suspend the tube in the
100-mL graduated cylinder
(see Figure 7).

www.carolina.com/distancelearning 13

Figure 7.

continued on next page

A

ACTIVITY

14 Carolina Distance Learning

6. Start a timer as you pour 10 mL of tap
water from the 10-mL graduated
cylinder into the plastic tube in the setup.

7. Record the time (in seconds) taken for the
first drop of water to emerge from the column,
and record this data in Data Table 2 of the
“Observations/Data Tables” section of the
Lab Worksheet. For some samples, this
could happen very quickly (even as you are
pouring), so keep a close eye on the sample
as you are pouring.

8. Repeat Steps 2–7 with the two remaining
samples (using new materials for each
sample).

ACTIVITY 3
pH Test Comparison of Soil
Samples

For Activities 3 and 4, use the soil from the
initial collection in the “Preparation” section
(“Soil Sample A”). For another soil sample
(this will be called “Soil Sample B”), collect
a sample of your choice—for example,
this can be commercial potting soil, soil
from a different outdoor location, or any
remaining clay from this lab. Avoid using
any remaining sand since it carries little
nutritional value due to its large pore
space.

Ideally, the best option would be to find
another soil sample from a different outdoor
location with contrasting properties. For
example, if “Soil Sample A” was from a very
dry area without plants, try to find a very
moist soil sample that is covered with grass

ACTIVITY 2 continued

A

for “Soil Sample B.” You can also select a
deeper soil sample for comparison with the
surface-based “Soil Sample A.”

1. Propose a hypothesis concerning which
of the two samples will be the more
acidic of the two and which one the more
basic. Explain your reasoning. Record
the hypothesis and reasoning in the
“Hypotheses” section of the Lab Worksheet.

2. Open the rapitest® Soil Tester kit.
3. Wearing PPE, remove the capsules from

one of the green-capped vials (the pH test
capsules).

4. Fill the vial with “Soil Sample A” up to the
first line.

5. Carefully open one of the green capsules and
pour the powder into the vial. (Do this over
the vial to prevent any spillage.)

6. Add distilled water up to the fourth line.
7. Cap the vial, and shake it thoroughly

(about 20 seconds).
8. Allow the soil to settle for approximately

one minute.
9. Compare the color of your sample to those

on the pH color chart on the back of the
rapitest® Soil Tester kit instructions (the
“Plant Food Color Chart”) to determine the
pH of the soil sample. Record this data in
Data Table 3 of the “Observations/Data
Tables” section of the Lab Worksheet.

10. Take a photograph of your vial held
up next to the “Plant Food Color
Chart.” Include in your photograph a strip of
paper with your name and the date clearly

continued on next page

www.carolina.com/distancelearning 15

Day 2
1. Wearing PPE, remove the caps from the

purple, blue, and orange vials from the
rapitest® Soil Tester kit and remove their
capsules.

2. Using a pipet from the equipment kit, fill each
vial up to the fourth line with the supernatant
(liquid above the soil) from the “Soil Sample
A” mixture made on Day 1.

3. Carefully separate the capsules, and pour the
powder into the corresponding-colored vials.
Make sure the colors of the capsules match
the respective vials. (Perform this step over
the vial to prevent spillage of the powder).

4. Cap the vial, and shake it thoroughly (for
about 20 seconds).

5. Allow color to develop for 10 minutes.
6. Use the “Plant Food Color Chart” on the back

of the rapitest® Soil Tester kit instructions
to determine the nutrient content of the soil
sample. Record this data in Data Table 4 of
the “Observations/Data Tables” section of the
Lab Worksheet.

7. Take a photograph of your vial held up
next to the “Plant Food Color Chart.”
Include in your photograph a strip of paper
with your name and the date clearly written
on it. You will be uploading this photograph to
your lab report.

8. Rinse the vials, and repeat Steps 1–7 with the
other soil mixture (“Soil Sample B”).

A

written on it. You will be uploading this
photograph to your lab report.

11. Dump out the soil mixture into the
household trash.

12. Rinse the vial, and repeat Steps 2–11 with
the other soil sample you chose (“Soil
Sample B”).

ACTIVITY 4
Nitrogen, Phosphorus, and Potash
Test Comparisons of Soil Samples

Consider your two soil samples, particularly in
terms of where you obtained them and their
appearance. Based on the characteristics
and what they have contained so far,
hypothesize which will have a higher level of
nutrients (nitrogen, phosphorus, and potash)
and which will have a lower level. Explain why,
and record your hypothesis in the “Hypotheses”
section of the Lab Worksheet.

Day 1
1. Fill a clean jar or can with 1 part

“Soil Sample A” and 5 parts water.
Thoroughly swirl the soil and water together
for 1 minute; then allow the mixture to settle
(approximately 24 hours).

2. Repeat Step 1 with “Soil Sample B” and a
different jar or can.

ACTIVITY

16 Carolina Distance Learning

Submission
Using the Lab Report Template provided,
submit your completed report to Waypoint
for grading. It is not necessary to turn in the
Lab Worksheet.

Disposal and Cleanup
1. Rinse and dry the lab equipment from the

equipment kit, and return the materials to
your equipment kit.

2. Discard the soil samples and any other
materials from the materials kit in the
household trash. The 10 mL graduated
cylinder and plastic tubes may be recyclable.

3. Sanitize the work space, and wash your
hands thoroughly.

www.carolina.com/distancelearning 17

ACTIVITY

Lab Worksheet
Hypotheses

Activity 1.

Activity 2.

Activity 3.

Activity 4.

continued on next page

ACTIVITY

18 Carolina Distance Learning

Data Table 3.

pH Comparison of Soil Samples

Soil Sample A Soil Sample B
(Location Description: _____________________________)

pH

Data Table 4.

Nitrogen, Phosphorus, and Potash Comparison in Soil Samples

Nitrogen Phosphorus Potash

Soil Sample A

Soil Sample B

Observations/Data Tables

Data Table 1.

Particle Size Distribution and Soil Type

Depth of
Clay Layer

(cm)

Depth of
Silt Layer

(cm)

Depth of
Sand Layer

(cm)

Total
Depth
(cm)

%
Clay

%
Silt

%
Sand

Soil
Texture

Soil
Sample A

Data Table 2.

Determination of Soil Porosity

Time Taken for First Drop to Emerge from Column (s)

Sand Sample

Clay Sample

Soil Sample A

NOTES

www.carolina.com/distancelearning 19

ENVIRONMENTAL SCIENCE
Properties of Soil: Agricultural and Water Availability Impacts

Investigation Manual

www.carolina.com/distancelearning
866.332.4478

Carolina Biological Supply Company
www.carolina.com • 800.334.5551
©2019 Carolina Biological Supply Company

CB781641908 ASH_V2.2

  • Properties of Soil: Agricultural and Water Availability Impacts
    • Table of Contents
    • Overview
    • Outcomes
    • Time Requirements
    • Key
    • Background
      • Soil Horizons and Chemical Composition
      • Identifying Soil Types: Texture and Structure
      • Processes Affecting the Fertility of Soil
    • Materials
      • Included in the materials kit:
      • Needed from the equipment kit:
      • Needed but not supplied:
    • Safety
    • Preparation
    • ACTIVITY 1
      • A Particle Size Distribution and Determination of Soil Texture
        • Day 1
        • Day 2
    • ACTIVITY 2
      • A Porosity of Different Soil Types
    • ACTIVITY 3
      • A pH Test Comparison of Soil Samples
    • ACTIVITY 4
      • A Nitrogen, Phosphorus, and Potash Test Comparisons of Soil Samples
        • Day 1
        • Day 2
    • Submission
    • Disposal and Cleanup
    • Lab Worksheet
      • Hypotheses
      • Observations/Data Tables
    • NOTES

Week 2 Assignment Template

Sustainable Living Guide Contributions, Part Two of Four:

Sustaining our Agricultural Resources

Instructions: Using the term that you have selected from the list provided in the classroom, please complete the following three-paragraph essay. Write a minimum of 5 to 7 well-crafted, original sentences per paragraph. In your response, you are expected to cite and reference, in APA format, at least two outside sources in addition to the class text. The sources must be credible (from experts in the field of study); at least one scholarly source (published in a peer-reviewed academic journal) is strongly encouraged. Delete all instructions before submitting your work to Waypoint.

Your Term: [type your term here]

[First Paragraph: Thoroughly define your term, using your own words to do so. In your definition, be sure explain why the term is important to know. Be as specific as possible and provide examples as necessary to support your ideas.]

[Second Paragraph: Discuss how the term affects living beings (including humans) and/or the physical environment. Provide examples as needed.]

[Third Paragraph: Suggest two clear, specific actions that you and the other students might take to promote environmental sustainability in relation to this term. Be creative and concrete with your suggestions. For example, you might recommend supporting a particular organization that is active in the field of your term. Explain exactly how those actions will aid in safeguarding our environment in relation to your chosen term.]

References: Following your essay, list all references you cited, in APA format.

After proofreading your assignment carefully, please submit your work to Waypoint for evaluation.

3 Managing Our Population and Consumption

sculpies/iStock /Getty Images Plus

Learning Outcomes

After reading this chapter, you should be able to

• Explain how and why the human population has changed over time.
• Define determinants of population change.
• Interpret an age-structure pyramid.
• Deconstruct how the demographic transition model explains population growth over time.
• Analyze the effectiveness of direct and indirect efforts to control population growth.
• Compare and contrast China’s and Thailand’s population policy.
• Describe how population size, affluence, and technology interact to impact the environment.

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70

Section 3.1 Population Change Through Time

At 2 minutes before midnight on Sunday, October 30, 2011, a 5.5-pound baby girl named Dan-
ica May Camacho was born in a government-run hospital in Manila, Philippines. Danica May
was just one of thousands of babies born in the Philippines that day and just one of hundreds
of thousands born around the world each day. Yet Danica May’s birth represented a milestone
for reasons that her parents could never have imagined. The United Nations Population Divi-
sion decided to symbolically designate Danica May as the world’s 7 billionth person and to
declare October 31, 2011, as the Day of Seven Billion to call attention to the issue of world
population growth. Danica May was greeted with a burst of camera flashes, applause from
hospital staff and United Nations officials, and a chocolate cake with the words “7B Philip-
pines” on it. Her stunned parents also received gifts and a scholarship grant for her future
education.

Was Danica May Camacho actually the world’s 7 billionth person? We will likely never know.
For the United Nations, determining the exact date and precise birth location of the world’s
7 billionth person was beside the point. The fact remains that about 250 babies are born
somewhere in the world every minute. This translates to 360,000 births every day and over
130 million new people on the planet every year. Because humans are dying at less than half
that rate—104 deaths per minute, 150 thousand per day, and 55 million per year—global
population is currently growing at a rate of roughly 75 million per year. In other words, we
are adding the equivalent of a new Germany or Vietnam to the global population each year.
Since Danica May symbolized the 7 billionth person in late 2011, the global population has
continued to grow to over 7.7 billion. Over 700 million more people have joined the human
family in time for Danica May’s seventh birthday.

Whether global population will continue to grow at this rate, slow, or even decline in the
decades ahead has enormous implications for the environment. The number of people on the
planet, combined with the resource and material consumption patterns of those people, are
key drivers of environmental change and an important subject in the study of environmental
science. This chapter will first review how human population has changed over time, increas-
ing gradually over tens of thousands of years before going from 1 billion to over 7 billion in
just the past 200 years. We’ll then examine human population growth using the science of
demography, the study of population changes and trends over time. Demography will help
us better understand how and why population has changed, and it also allows us to examine
what might happen to population in the future. This will be followed by a discussion of popu-
lation policy and fertility control, utilizing case studies of countries around the world that
have responded in different ways to changing population patterns. Finally, we will consider
how population growth, combined with resource and material consumption patterns, affects
the natural environment. We’ll see that absolute numbers of people in a given population are
just one factor in determining the impact that population will have on the environment.

3.1 Population Change Through Time

Recall from Chapters 1 and 2 that many environmental scientists describe the period we live
in as the Anthropocene, or the age of humans. Human activities are now the dominant influ-
ence on the environment, the oceans, the climate, and other Earth systems. We have converted
large areas of the planet’s surface to cities, suburbs, farms, and other forms of development.

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71

Section 3.1 Population Change Through Time

The waste products of our modern industrial society, including radioactive and other long-
lived wastes, can be detected in even some of the most remote locations of the globe. Our
activities are fundamentally altering the chemical composition of the world’s atmosphere,
oceans, and soils. And we are now driving other species to extinction at rates that are 100 to
1,000 times greater than “normal” or background rates of extinction.

It may come as some surprise then to consider that for much of human history our very sur-
vival as a species was in question. We can divide human history into three broad periods: the
preagricultural, the agricultural, and the industrial.

Preagricultural Period
The preagricultural period of human history dated from over 100,000 years ago to about
10,000 years ago. During this time, humans developed primitive cultures, tools, and skills
and slowly migrated out of Africa to settle Europe, Asia, Australia, and the Americas. Disease,
conflict, food insecurity, and environmental conditions kept human numbers low, perhaps as
low as 50,000 to 100,000 across the entire planet. That’s about the same as today’s population
of a small city in the United States, such as Albany, New York; Trenton, New Jersey; Roanoke,
Virginia; or Tuscaloosa, Alabama. By the end of the preagricultural period about 10,000 years
ago, the human population across the globe had risen to roughly 5 million to 10 million, about
the same as New York City today.

Agricultural Period
The agricultural period of human history, starting about 10,000 years ago, set the stage for
more rapid growth in human numbers. The domestication of plants and animals, selective
breeding of nutrient-rich crops, and the development of technologies like irrigation and the
plow greatly increased the quantity and security of food supplies for the human population.
By the year 5000 BCE (7,000 years ago), there were perhaps 50 million people on the planet.
By 2,000 years ago, that number may have risen to 300 million, about the same as the popu-
lation of the United States today. Despite the advances brought on by the agricultural revo-
lution, population growth remained low due to warfare, disease, and famine. For example,
between 1350 and 1650, a series of bubonic plagues known as the Black Death ravaged much
of Europe, killing as much as one third of the continent’s population. High birth rates helped
offset high mortality rates, and by the end of the agricultural period 200 years ago, global
population stood at close to 1 billion (Kaneda & Haub, 2018).

Industrial Period
The introduction of automatic machinery around the middle of the 18th century ushered in
the industrial period, the period we are still in today. A combination of factors has caused
dramatic increases in the human population during this time. The Industrial Revolution led to
sharp increases in food production. Advances in science resulted in improved medicines and
medical care. Better understanding of communicable diseases prompted improvements in
sanitation and water quality. All of these developments helped extend life expectancy, reduce

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72

Section 3.1 Population Change Through Time

mortality rates, and decrease infant mortality. However, because birth rates did not drop at
the same time, human population began to grow more dramatically (see Figure 3.1). While
it took all of human history—over 100,000 years—to reach a global population of 1 billion
around the year 1800, it took only about 120 years to double that number to 2 billion in 1927.
Thirty-three years later, in 1960, world population reached 3 billion. Since 1960 another bil-
lion people have been added to the population every 12 to 14 years—1974, 1987, 1999, and
2011 (Population Reference Bureau, 2018).

Figure 3.1: Human population growth

The human population began to increase dramatically starting in the industrial period.

Based on data from “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content
/uploads/2018/08/2018_WPDS.pdf).

5 million

8000
BCE

5000
BCE

100
CE

1250
CE

1400
CE

1600
CE

1650
CE

1850
CE 19

30

19
74

19
99

2
01

1

2
01

9

8

7

6

5

4

3

2

1

0

Year

Preagricultural
period

Agricultural
period

Industrial
period

H
u

m
an

p
o

p
u

la
ti

o
n

(
b

ill
io

n
s)

7 billion

7.7 billion

6 billion

4 billion

2 billion

1.1 billion
470 million

350 million
400 million

300 million
50 million

545 million

Predicting when the 8, 9, or 10 billionth person will be added to the world’s population
depends on assumptions about human fertility and health trends. The decisions that young
people make today about when and if to marry, whether to use contraception and family
planning, and how many children to have will influence future changes to the population. The
United Nations Population Division (2017) now projects that world population will grow to
8.6 billion by 2030, 9.8 billion by 2050, and 11.2 billion by 2100. Whether we hit the 11.2 bil-
lion mark in 2100, far surpass it, or never actually reach it at all will depend in large part on
decisions made by what is known as the “largest generation.” As of 2018, well over 40% of
the world’s population was younger than 25 years old, and nearly 2 billion people were under
age 15 (United Nations Population Division, 2017). How the decisions made by these young
people will affect future global population is the focus of Section 3.2.

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73

Section 3.2 Demographics

3.2 Demographics

The science of demography focuses on the statistical study of human population change. The
word demography is derived from the Greek words demos (“people”) and graphy (“field of
study”). A demographer is a person who studies demography, and demographers focus their
research on demographic trends and statistics. As complex as the study of human populations
may seem, it really boils down to understanding a handful of variables and measures that
together determine changes in human numbers.

Birth and Death
The most basic determinants of a change in any given population are birth rates and death
rates. Demographers measure births and deaths in a very specific way, using what they call
crude birth rates and crude death rates. The crude birth rate (CBR) is the number of live
births per 1,000 people in a given population over the course of 1 year. Likewise, the crude
death rate (CDR) is the number of deaths per 1,000 people in a given population over the
course of 1 year.

The best way to illustrate how CBR and CDR interact to determine population change is
through a simple example. Imagine a small village or town cut off from the outside world. At
the start of the year, there were 1,000 people in this village, but over the next 12 months, 20
children were born and 8 people died. How do these numbers translate into CBR and CDR?
What does this mean for the overall population and rate of population growth? In this case,
the CBR would be 20 and the CDR would be 8. The rate of population growth, what demogra-
phers call the rate of natural increase—birth rates minus death rates, excluding immigra-
tion and emigration—would be CBR – CDR, or 20 – 8 = 12, or 1.2% of the population of 1,000,
leaving the population of the village at the end of the year to be 1,012.

Migration
In reality, towns and villages are typi-
cally not cut off from the outside world, so
demographers also consider immigration
and emigration as factors in population
change. Immigration is people moving
into a given population, while emigration
is people moving out of that population. As
with the rate of natural increase, demogra-
phers determine the net migration rate
as the difference between immigration and
emigration per 1,000 people in a given pop-
ulation over the course of 1 year.

Karen Kasmauski /SuperStock
When calculating population change,
immigration and emigration must also
be considered.

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74

Section 3.2 Demographics

Fertility
Another important statistic that demographers focus on is the total fertility rate (TFR). The
TFR is the average number of children an individual woman will have during her childbear-
ing years (currently considered to range from age 15 to 49). In preindustrial societies, fertil-
ity rates were often as high as 6 or 7. This was due to a number of factors. Since most were
engaged in labor-intensive agriculture, large families were considered an asset. Because so
many children died in infancy or childhood, women tended to have more children to ensure
that at least some would survive. Earlier age at marriage, lack of contraception, and cultural
factors also played a role in high fertility rates. Yet human populations grew slowly or not at
all in preindustrial societies because death rates were also high.

It may seem like fertility rates (TFR) and birth rates (CBR) are measuring the same thing,
but that’s not the case. Recall that CBR is the number of births per 1,000 people in a given
population over 1 year. TFR is the average number of children an individual woman will have
during her childbearing years. A given population could be characterized by a high TFR and
a low CBR if there were very few women of childbearing age. Likewise, there could be a low
TFR and a high CBR if a large percentage of the population were women of childbearing age.

Age-Structure Pyramids
The link between fertility rates, the age structure of a population, and overall birth rates
has led demographers to develop a visual tool they call an age-structure pyramid. Age-
structure pyramids, also called population pyramids, are a simple way to illustrate graphi-
cally how a specific population is broken down by age and gender. Each rectangular box in an
age-structure pyramid diagram represents the number of males or females in a specific age
class—the wider the box is, the more people there are.

Age-structure pyramid diagrams for Uganda, the United States, and Japan are shown in Figure
3.2. Demographic data on CBR, CDR, TFR, immigration, and emigration for these countries are
listed in Table 3.1. Demographers looking at these three age-structure pyramids could tell you
immediately that Uganda is experiencing high rates of population growth, the United States
is growing slowly or is stable, and Japan’s population is in decline. How do they know this?

Table 3.1: Demographic data for Uganda, the United States, and Japan

Country
CBR

(per 1,000)
CDR

(per 1,000) TFR

Net migration
rate

(per 1,000)

Rate of natural
increase

(percentage)

World 19 7 2.4 N/A 1.2

Uganda 41 9 5.4 –1 3.2

United States 12 9 1.8 3 0.3

Japan 8 11 1.4 1 –0.3

Source: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content/uploads
/2018/08/2018_WPDS.pdf).

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75

Section 3.2 Demographics

Figure 3.2: Age-structure pyramids for Uganda, the United States,
and Japan

The age-structure pyramids for these three countries can tell us what to expect of each country’s
population growth.

Data from “International Data Base,” by US Census Bureau, 2018 (https://www.census.gov/data-tools/demo/idb/informationGateway.php).

Uganda – 2018Male Female

4.0 4.03.2 3.22.4 2.41.6 1.60.8 0.80

100+
95–99
90–94
85–89
80–84
75–79
70–74
65–69
60–64
55–59
50–54

40–44
45–49

35–39
30–34

20–24
25–29

15–19
10–14
05–09
00–04

04.8 4.8

United States – 2018

Age Group Population (in millions)Population (in millions)

Age Group Population (in millions)Population (in millions)

Age Group Population (in millions)Population (in millions)

Male Female

15 1512 129 96 63 30

100+
95–99
90–94
85–89
80–84
75–79
70–74
65–69
60–64
55–59
50–54

40–44
45–49

35–39
30–34

20–24
25–29

15–19
10–14
05–09
00–04

018 18

Japan – 2018Male Female

5 54 43 32 21 10

100+
95–99
90–94
85–89
80–84
75–79
70–74
65–69
60–64
55–59
50–54

40–44
45–49

35–39
30–34

20–24
25–29

15–19
10–14
05–09
00–04

06 6

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76

Section 3.2 Demographics

Uganda
In the case of Uganda, the large numbers of people in the age classes for 0–4, 5–9, and 10–14
years suggest that the fertility rate and birth rate must be high, and the data in Table 3.1
confirms this. When the TFR is much higher than 2, it means that women in that population
are having more children than are needed to “replace” the parents and maintain a certain
population. This is why demographers typically refer to 2 as the replacement rate. Uganda’s
fertility rate of 5.4 means that, on average, each woman of childbearing age in that country is
giving birth to more than 5 children over her lifetime. And because this number is far higher
than the replacement rate of 2, Uganda’s population is growing at an annual rate of 3.2%.

Even if fertility rates in Uganda were to be immediately reduced to around 2, the population
would continue to grow for a few more decades because there are so many female children
below age 15. This large number of young girls who have yet to enter their childbearing years
creates built-in momentum for population growth, which demographers refer to as demo-
graphic momentum.

United States
The situation in the United States looks quite different than that of Uganda. Instead of being
wide at the bottom, the age-structure pyramid for the United States is fairly even for ages
between 0 and 70 or 75. This suggests that fertility rates in the United States must be close to
the replacement rate and that birth rates and death rates are roughly similar to each other. The
data in Table 3.1 confirms this. The fertility rate in the United States of 1.8 even suggests that
the United States is below the replacement rate. If fertility rates in the United States remain
at current levels, and if net migration stays the same or declines, the population growth rate
in the United States will approach zero and possibly even turn negative in the years ahead.

Japan
On the complete opposite end of the spectrum from Uganda is Japan. Japan’s age-structure
pyramid actually gets wider at the middle and upper portions, suggesting that fertility rates
are well below replacement levels and that overall population is stable or declining. Table 3.1
confirms this. The TFR in Japan is currently 1.4, and the CBR of 8 is lower than the CDR of 11.
Overall, Japan’s population is currently declining at a rate of –0.3% annually, with moderate
levels of positive net migration helping slow the rate of population decline.

Learn More: Visualizing Population Growth

After reviewing all of the demographic terms and concepts, it might seem challenging to try
to put them together and get a picture of how human populations change over time. This
very simple video developed by National Public Radio at the time when world population
hit 7 billion does a very good job of helping show how populations can change over time in
response to just a handful of changing demographic factors—namely birth rates and death
rates. See if the concepts presented help reinforce the material you just finished reading.

https://www.npr.org/2011/10/31/141816460/visualizing-how-a-population-grows-to-7-billion

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77

Section 3.3 The Demographic Transition

3.3 The Demographic Transition

For most of human history, both birth rates and death rates were relatively high, resulting in
slow population growth. It was not until the time of the Industrial Revolution that this rough
balance between birth and death rates begin to shift dramatically. Life expectancies increased
and infant mortality and overall death rates declined—but birth rates generally remained
high. In other words, the sudden increase in global population from 1 billion to over 7 bil-
lion in just 200 years was not because people started having more children, but because of
a divergence or widening gap between birth rates and death rates as fewer people died. At
first, most of this population increase was concentrated in the more industrialized, developed
countries, where advances in food supply, medicine, and sanitation were more widespread.
By the second half of the 20th century, this population growth began occurring in developing
countries as these advances became available there as well.

Demographers use a model called the demographic transition to explain and understand the
relationship between changing birth rates, death rates, and total population (see Figure 3.3).
Phase 1 of the demographic transition model shows how human populations in preindustrial
societies were generally characterized by high birth and death rates. These tended to cancel
out one another and resulted in a fairly stable population. In Phase 2, as death rates begin
to decline and birth rates remain high, the population increases. In Phase 3, as populations
become more urbanized and as expectations of high infant mortality decline, birth rates also
begin to drop. However, birth rates still exceed death rates, resulting in a continued natural
increase in the population. Not until Phase 4 of the demographic transition do birth rates and
death rates begin to converge again, and overall population begins to show signs of stabilizing.

Figure 3.3: The demographic transition

The four stages of demographic transition show the change in population growth that a country
experiences over time as it develops and industrializes.

Phase 1:
Preindustrial

Phase 2:
Transitional

Phase 3:
Industrial

Phase 4:
Postindustrial

50

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78

Section 3.3 The Demographic Transition

Contributing Factors
It’s instructive to review some of the main factors that trigger changes in birth and death rates
and move countries through various stages of the demographic transition.

A population’s death rate will generally begin to drop when three things happen.

1. The food supply increases and becomes more stable.
2. Sanitation practices, such as sewage treatment, improve.
3. Advances in medicine, such as the development and use of antibiotics, occur.

All these factors were prevalent in developed countries during the latter part of the 19th
century and into the 20th century, and death rates declined accordingly. For example, death
rates in the United States were roughly 29.3 for every 1,000 people in 1850, and the average
life expectancy at birth at that time was only about 40. By 1900 death rates had dropped to
17.2, and life expectancy at birth had increased to about 50. After U.S. death rates spiked to
almost 20 during a global influenza outbreak in 1918, they continued to drop to 8.4 by 1950,
roughly where they remain to this day, along with an average life expectancy of 78.7 (Arias,
Xu, & Kochanek, 2019).

While we might expect birth rates to drop at roughly the same rate and at the same time as
death rates, birth rates often remain high due to cultural factors, a desire for large families
in rural households, and expectations of high infant mortality. Over time, however, cultural
attitudes toward family size can change. Likewise, the need for a large family decreases as a
population urbanizes and fewer people are engaged in labor-intensive agriculture. Finally,
infant and child mortality rates fall as sanitation and medical care improve.

Developed Countries Versus Developing Countries
The United States and other developed countries were well into Phase 2 or 3 of the demo-
graphic transition by the start of the 20th century. Today these countries are in Phase 4, with
very low fertility rates, low birth rates, and low death rates. In contrast, many developing
countries were still in Phase 1 or 2 of the demographic transition as late as 1950. These coun-
tries had not seen the advances in medicine, food supply, clean water, and sanitation that the
developed countries had achieved. In addition, many developing countries were still largely
rural and dependent on agriculture, a situation that tends to promote high fertility and large
family size. As a result, developing countries were characterized by high birth and death rates.
From roughly 1950 onward, however, developing countries began to enter Phases 2 and 3 of
the demographic transition, and their populations increased rapidly as a result. Today some
developing countries, especially in Asia, are approaching or have already reached Phase 4 of
the demographic transition. Meanwhile, others—especially in sub-Saharan Africa—could still
be categorized as being in Phase 2 or 3.

Table 3.2 provides comparative demographic data for the world as a whole and for seven
countries in different stages of the demographic transition. The West African country of Mali
can still be said to be in Phase 2 of the demographic transition. Fertility and birth rates are
still high, but improved access to medicine, sanitation, and food has dropped death rates to

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79

Section 3.3 The Demographic Transition

almost the world average. As a result, Mali’s population is growing at a rapid rate of 3.5% and
will double every 20 years if the growth rate remains the same. Senegal, also in West Africa,
and Egypt in North Africa are moving from Phase 2 to Phase 3 of the demographic transition
as fertility rates and birth rates have begun to decline in recent years. India is now solidly
in Phase 3 of the demographic transition, since fertility rates have dropped to 2.3 and birth
rates to 20 per 1,000. However, because India has a relatively young population—the age-
structure pyramid is wider at the bottom—there is some built-in demographic momentum.
As a result, India, already the second most populous country in the world after China, will
become the most populous around the year 2022. The Southeast Asian nation of Malaysia is
further along in the demographic transition than India. Meanwhile, countries like Denmark
and South Korea are clearly already in Phase 4, a situation characterized by low fertility, low
birth and death rates, and stable or even declining populations.

Table 3.2: Demographic data for countries in different phases

Country CBR CDR TFR

Rate of
natural

increase

Demographic
transition

phase

World 19 7 2.4 1.2 3/4

Mali 45 10 6.0 3.5 2

Senegal 33 6 4.6 2.7 2/3

Egypt 27 6 3.4 2.1 2/3

India 20 6 2.3 1.4 3

Malaysia 16 5 1.9 1.1 3/4

Denmark 11 9 1.8 0.2 4

South Korea 7 6 1.1 0.1 4

Sources: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content/uploads
/2018/08/2018_WPDS.pdf); “International Data Base,” by US Census Bureau, 2018 (https://www.census.gov/data-tools/demo
/idb/informationGateway.php).

Because virtually all developed countries are in Phase 4 of the demographic transition, and
because most developing countries are still in Phases 2 or 3, demographers predict with
confidence that virtually all the world’s population growth in the decades ahead will be in
developing countries (see Figure 3.4). Close to 60% of that global increase in population will
take place in Africa, with smaller increases in Asia and the Americas. Europe’s population is
projected to decline by about 16 million—not surprising, given the low fertility rates in most
European countries. These are all projections, however. How much population growth will
actually occur, and how fast we reach 8, 9, or 10 billion, will depend on how quickly devel-
oping countries move through the demographic transition. The speed of a country’s demo-
graphic transition will ultimately depend on the decisions made by young people in those
countries. Section 3.4 will cover the role of population policy in affecting those decisions and
“speeding up” the demographic transition.

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80

Section 3.4 Population Policy and Fertility Control

3.4 Population Policy and Fertility Control

As recently as the 1950s, an average woman anywhere on the planet gave birth to almost 6
children during her childbearing years. That global average has now declined to 2.4, with
average fertility rates ranging from 1.6 in developed countries to 2.7 in developing countries.
The United Nations predicts that average global fertility rates will continue to decline toward
a replacement rate of 2 in the decades ahead and that, as a result, world population could
stabilize by the end of this century at around 11 billion.

However, slight changes in fertility rates can have a profound impact on demographic trends.
An increase in average fertility of just 0.5 children per woman could lead to a global popula-
tion of over 15 billion by 2100. Likewise, a decrease in average fertility of 0.5 would result in
a global population of 6.2 billion by 2100, over 1 billion less than today. Any effort to influence
fertility rates, whether direct or indirect, can have a significant impact on future population
trends. Efforts to control and influence population change usually invite controversy since
they affect highly individual and personal behavior. Population policy is also often subject to
scrutiny and criticism on religious and moral grounds. This section reviews the major factors
that appear to influence fertility rates and the policy efforts to change them.

Figure 3.4: World population, 1950–2100

Demographers expect much of the world’s population growth to come from developing countries, as the
population in more developed countries stabilizes or even declines.

Data from “World Population Prospects: The 2017 Revision,” DVD edition, by United Nations, Department of Economic and Social Affairs,
Population Division, 2017 (https://population.un.org/wpp/Download/Standard/Population).

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1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 20602050 2070 2080 2090 2100

Year

Less developed countries

More developed countries

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81

Section 3.4 Population Policy and Fertility Control

Direct Versus Indirect Factors
Broadly speaking, factors that influence fertility are either direct or indirect. Direct factors are
those that have an immediate and tangible impact on a woman’s decision or ability to have
children. These mainly include the availability and affordability of contraception and family
planning services. In some countries, such as China, contraceptive availability has also been
linked with government incentives (and disincentives) to encourage couples to have fewer
children (see the case study in Section 3.5). The availability of family planning services, com-
bined with incentives to have fewer children, has led to dramatic reductions in fertility rates
in China, from roughly 5 children per woman in the 1970s to only 1.8 today.

In contrast, indirect factors are those that change the context within which women and couples
make decisions about fertility and family size. For example, increasing girls’ access to educa-
tion results in lower fertility rates (see Figure 3.5). Young women who are better educated
tend to marry later and have greater employment opportunities, both of which help reduce
fertility. On average, globally, women with no formal education have 4.5 children. Those
who have some schooling have an average of 3 children, and those who have some second-
ary schooling have an average of only 1.9 children. For women with advanced schooling, the
average fertility rate drops to 1.7. In this case, investment in providing increased educational
opportunities can be thought of as an indirect form of population control.

Figure 3.5: Education and fertility rates, 2012–2016

Data from select developed and less developed countries show a clear relationship between female
education and fertility rates.

Data from UNESCO Institute for Statistics, Data Center, n.d. (http://data.uis.unesco.org).

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Percent enrollment in secondary school

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82

Section 3.4 Population Policy and Fertility Control

Early Population Policies
As discussed earlier, by 1950 most developing countries were still in Phase 1 or 2 of the demo-
graphic transition. In the decades that followed, rapid improvements in medicine, sanitation,
food supply, and water quality dramatically lowered death rates in these countries and trig-
gered an exponential increase in population. The overall population of developing countries
doubled from 1.7 billion in 1950 to 3.4 billion by 1980. Faced with a ballooning population
and concerned with issues like food security, public services, and health, many developing
countries undertook a variety of direct efforts to reduce fertility and slow population growth.
China’s one-child policy was the most publicized, but other countries like Brazil, Mexico,
Iran, and Indonesia have also attempted to reduce fertility through monetary incentives and
increased availability of contraceptives and family planning services.

India attempted a much more coercive approach in the 1970s. India’s government declared
emergency rule in 1975 and ordered local governments to set quotas for forced steriliza-
tions—vasectomies for men and tubal ligation for women—for couples with more than three
children. Couples who failed to undergo sterilization after their third child were threatened
with fines and imprisonment, and in some cases police were sent to round up men and women
and force them to undergo sterilization. In the last 6 months of 1976 alone, more than 6.5 mil-
lion people were sterilized in India, and it’s estimated that thousands may have died from
infections associated with the surgery (Hartmann, 1995). The sterilization campaign proved
so unpopular that it triggered protests and riots in various regions of the country. By 1977
public displeasure with the sterilization program helped lead to the electoral defeat of the
ruling party and a backlash against family planning programs in general in India.

The Shift to an Indirect Approach
The year 1994 was a turning point in the field of population policy. In that year the United
Nations International Conference on Population and Development (ICPD) was held in Cairo,
Egypt. The ICPD was attended by close to 20,000 delegates representing government agencies,
NGOs, and the media. The conference is widely credited with shifting the focus of population
policy from direct and sometimes coercive
measures to broader efforts to address the
basic needs of the world’s poorest residents.

The ICPD resulted in a consensus program
of action containing over 200 recommen-
dations and goals in the areas of women’s
health, development, and social welfare.
These included providing universal access
to primary education for girls and increased
access to secondary and higher education for
girls and women; providing universal access
to reliable, affordable, and safe family plan-
ning services; reducing infant and maternal
mortality; and increasing women’s access
to employment opportunities and financial
credit. Many delegates to the ICPD believed

Pavel Rahman/Associated Press
Family planning programs, such as this one in
Bangladesh, are an opportunity for women to
learn about contraception and other family
planning services.

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83

Section 3.4 Population Policy and Fertility Control

that these actions would increase women’s status in society and result in greater empower-
ment of women in making decisions about their own fertility.

Compared with earlier population policies, the ICPD recommendations emphasized indi-
rect means of reducing fertility. Increased levels of education delay both the age of marriage
and the age at which a woman has her first child. This narrows the reproductive window for
women and results in lower fertility rates on average. Providing safe and affordable family
planning services will also have an obvious impact on fertility.

Reducing infant mortality might seem to be a counterintuitive way to address population
growth. However, fertility rates are usually highest in societies with high infant mortality,
since parents seek to compensate for the expected loss of some of their children. Reducing
infant and child mortality through better health care provides some assurance to parents that
their children will survive to adulthood, and it reduces fertility rates in the process.

Finally, providing women with employment and small business opportunities has also been
demonstrated to reduce fertility (Phan, 2013; Upadhyay et al., 2014). Efforts in this area often
take the form of micro-credit or micro-lending programs that lend small amounts of money
to individuals or groups of women to start their own business. Giving women more economic
independence carries over to decisions about fertility, empowering them to resist spousal
and societal pressure for large families. (For more on this, check out Apply Your Knowledge:
What Is the Connection Between Female Employment and Fertility Rates?)

Apply Your Knowledge: What Is the Connection Between
Female Employment and Fertility Rates?

Looking at some fertility rate data from around the world will help us learn more about
some of the indirect factors that influence population growth and allow us to practice some
strategies for analyzing data sets.

Figure 3.6 shows two charts with data on TFRs and factors that may be influencing those
rates around the world. The charts contain data points from several different countries so
that we can explore female employment and CO2 emissions as possible influencing factors.
Based on these charts, do you think female employment and CO2 emissions are influencing
TFRs? If so, can you explain how? Can you use this information to come up with any
population management strategies?

You might notice that these figures both seem to show strong trends in the data. It appears
that countries with higher female employment tend to have lower fertility rates. It also
appears that countries with greater CO2 emissions tend to have lower fertility rates. Best fit
lines (also called trend lines), like the ones seen in our figures, can be helpful tools for finding
relationships like these. By definition, a best fit line traces a path through the middle of a data
set. When a best fit line slopes upward or downward and most of the data points fall close to
the line, this suggests that the two measurements are related somehow. Researchers say that
the data is correlated when one of these relationships exists. In this example, it is safe to say
that female employment and CO2 emissions both appear to be correlated with fertility rates.

(continued)

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84

Section 3.4 Population Policy and Fertility Control

Apply Your Knowledge: What Is the Connection Between
Female Employment and Fertility Rates? (continued)

Figure 3.6: Female employment, CO2 emissions, and fertility

Total fertility rates plotted against female employment (a) and CO2 emissions (b).

Data from “Children per Woman (Total Fertility Rate),” by Gapminder, n.d. (http://gapm.io/dtfr); “ILOSTAT,” by International
Labour Organization, 2019 (https://www.ilo.org/ilostat); “Fossil-Fuel CO2 Emissions,” by Carbon Dioxide Information Analysis
Center, 2017 (http://cdiac.ornl.gov/trends/emis/meth_reg.html).

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(a)

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(continued)

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85

Section 3.4 Population Policy and Fertility Control

Overall, these indirect approaches also tend to reduce poverty, and there are clear statistical
links between reduced poverty and lower fertility. The fundamental argument behind the
ICPD program of action is that “development is the best contraceptive,” as Indian politician
Dr. Karan Singh once said (as cited in Mathai, 2008, para. 3). Investments in education, health
care, sanitation, and economic opportunity are promoted as paying a “double dividend.” Not
only do they serve to lower fertility rates, they also meet social justice objectives of providing
a better life for the world’s poorest citizens.

Both direct and indirect efforts to lower fertility have been successful. With the exception
of mainly countries in sub-Saharan Africa, fertility rates have fallen to near or even below
the replacement rate in the majority of developing countries. But even as this has happened,
there has been something of a shift in the debate over population growth and the environ-
ment. More and more observers are pointing to high material consumption rates in devel-
oped countries as the greatest threat to the global environment, as opposed to high popula-
tion growth rates in developing countries. That debate is covered in Section 3.6, after the
comparative case study of family planning approaches in Section 3.5.

Apply Your Knowledge: What Is the Connection Between
Female Employment and Fertility Rates? (continued)

We often expect to see correlated data when there is a cause-and-effect relationship at play.
For example, our female employment and fertility data are correlated, and there is also a
strong theory for how female employment might cause a decrease in a region’s fertility
rates. More women working means that more women are financially independent. With
more financial freedom, more women might choose to delay or avoid getting married and
having children.

This cause-and-effect relationship can also be supported with studies that have explored
female employment in greater depth. In one recent example, researchers studied rural
communities in Senegal. By surveying them about their family sizes and lifestyle choices, the
researchers found that the relationship held up (Van den Broeck & Maertens, 2015).

When we have correlated data and supporting evidence of a cause-and-effect relationship,
we might conclude there is a causal relationship between the two measurements in a data
set. Causal relationships can be very useful from a policy standpoint. If we determined that
a causal relationship exists between female employment and fertility, we might develop job-
training programs and fair hiring regulations to exploit this relationship.

It is critical to realize that correlated data does not necessarily imply a causal relationship.
As researchers, we have to remember the mantra “correlation is not causation” so that we
do not draw conclusions based on relationships that do not exist. On the second chart, it
appears that the countries with greater emissions have lower fertility rates. However, there
is no obvious explanation for how CO2 emissions might impact reproduction. Countries often
undergo changes that impact both CO2 emissions and fertility rates at the same time, but this
does not mean that CO2 emissions are causing reproductive changes. As a result, we have
no reason to believe that we can change fertility rates by encouraging people to burn more
fossil fuels.

When analyzing data sets, you need more than a statistical correlation in order to identify a
causal relationship. You also need a strong theory and supporting evidence.

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86

Section 3.5 Case Study: Population Policies in China and Thailand

3.5 Case Study: Population Policies in China and Thailand

China has perhaps the most well-known and controversial population control program in the
world. China is currently the world’s most populous nation, with a 2019 population of 1.39
billion people, roughly one fifth of the world’s total. But it’s possible that China’s population
would be closer to 2 billion today had it not taken steps to reduce fertility and birth rates
more than 40 years ago. After suffering through famines that killed as many as 30 million
people in the 1960s, China launched a number of family planning campaigns that culminated
in a one-child-per-family policy in 1979. This policy relied on a variety of rewards and pun-
ishments to encourage compliance. Families with only one child were provided with better
access to health care, education, housing, and employment opportunities. Families with more
than one child lost these privileges and were also subject to fines. There were some excep-
tions to and differences in application of this policy. For example, rural couples were more
likely to be allowed a second child compared to urban couples. By 2015 China had begun to
relax the one-child rule, and all couples are now allowed to have two children.

While China’s one-child policy was successful in rapidly reducing the country’s fertility
rates—from over 5 in 1970 to 1.8 today—it has also been criticized on human rights and
other grounds. Zealous enforcement in the policy’s early years often resulted in forced abor-
tions and mass sterilizations such as those that occurred in India. In 1991, 12.5 million Chi-
nese citizens underwent sterilization, oftentimes against their will and under threat of vio-
lence and official brutality. A cultural preference for sons has also led to high rates of selective
abortions of female fetuses, large numbers of female babies being given up for adoption, and
even female infanticide—the deliberate killing of a child within its first year. China has per-
haps the most unbalanced male–female sex ratio in the world, with approximately 115 boys
for every 100 girls. As a result, millions of Chinese men have been unable to find a spouse and
have children. In China these men are known as guang gun-er, or literally “bare branches,”
since they are branches of a family tree that are unable to bear fruit.

As China was instituting its one-child policy, the Southeast Asian nation of Thailand was
adopting a very different approach to population policy. Like China, in 1970 Thailand had
high fertility rates (almost six children per
woman) and a population that was increas-
ing by more than 1 million people every
year. The Thai minister of health at the time,
Mechai Viravaidya, launched a humorous
public relations campaign to increase the
availability and use of contraceptives. He
founded the Population and Community
Development Association (PDA) to carry
out this work. PDA workers crisscrossed
the country handing out condoms, holding
family planning education clinics, spon-
soring condom balloon-blowing contests,
and painting birth control advertisements
on buses, billboards, and even the sides
of water buffalo. The PDA used humor to
encourage a more open discussion in polite
Thai society about the use of contraception.

Jerry Redfern/LightRocket/Getty Images
The Population and Community Development
Association in Thailand aims to educate
the population about family planning by
making contraception more accessible and
encouraging positive discussions.

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87

Section 3.6 Population Growth and Material Consumption

The association combined this campaign with projects to promote economic development
and education in order to encourage families to consider having fewer children. By just about
any measure, Mechai’s campaign could be considered a success. Thailand’s fertility rate is
now only 1.5, and condoms are now affectionately known in that country as mechais in honor
of Mechai’s work.

3.6 Population Growth and Material Consumption

The link between population growth and environmental degradation would seem obvi-
ous. More people consume more energy, food, water, and resources. More people also gen-
erate more pollution and waste products. For these reasons, efforts to slow and eventually
halt global population growth are often near the top of the agenda for many environmental
organizations.

However, the relationship between population size and environmental impact is not always
so clear. Some of the most sparsely inhabited regions are subject to some of the worst environ-
mental degradation in the world, such as widespread deforestation in the Brazilian Amazon
jungle. Meanwhile, some of the most densely populated regions, such as the island of Java in
Indonesia or Machakos District in Kenya, have been practicing relatively sustainable resource
management for decades or even centuries. This section will shift the discussion from a focus
on demography and population policy to a review of the ways in which population levels and
population change affect environmental conditions.

Population, Affluence, and Technology
In 1968, as the global population was swiftly climbing from 3 billion to 4 billion and beyond,
ecologist Paul Ehrlich wrote a book titled The Population Bomb. Ehrlich argued that runaway
population growth would result in increased starvation, social unrest, and even the collapse
of some societies as human numbers exceeded the carrying capacity of the local environment.
Ehrlich argued for quick and decisive action to limit further population growth, including
some of the more drastic and direct population policies described in Section 3.4. In the years
that followed the publication of The Population Bomb, the most dramatic predictions in the
book did not materialize. Advances in agriculture and increased global trade in food products
averted the kinds of widespread famines and food shortages that Ehrlich predicted, although
small-scale famines were still a reality. In addition, Ehrlich, working in partnership with fel-
low ecologist John Holdren, began to consider how other factors beyond just the numbers of
people could be affecting environmental conditions.

By the mid-1970s Ehrlich and Holdren were arguing that high rates of material consumption
and affluence in wealthy countries may actually play a greater role in global environmental
degradation than growing populations in poorer countries. They developed a simple equa-
tion called the IPAT formula (pronounced i-pat) to illustrate this argument. The I in the for-
mula stands for the environmental impact of a given population. Impact is a function of three
factors: population size (P), average affluence (A) or consumption rates per person, and the
kinds of technology (T) available.

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88

Section 3.6 Population Growth and Material Consumption

While poorer countries with high rates of population growth may be impacting the envi-
ronment through the P factor, wealthy countries have a larger impact through the A fac-
tor of affluence and consumption. The technology, or T, factor manifests in different ways.
For example, affluence allows a population to invest more resources in things like pollution
control and energy efficiency technology, potentially reducing environmental impact. At the
same time, affluence could also result in fundamental changes in the kinds of technologies
used by the average citizen, sometimes with profoundly negative effects on the environment.
For example, as countries like China and India have become more affluent, many individu-
als have shifted from relying on bicycles to relying on motorcycles and automobiles. Close to
Home: Examining Consumption provides another example of how affluence and consumption
affect the environment.

monkeybusinessimages/iStock /Getty Images Plus
In the image on the right, a father and daughter in rural India enjoy electricity for the first
time. There is a wide variance in consumption patterns between the wealthiest and poorest
people on the planet.

stockimagesbank/iStock/Getty Images Plus

Close to Home: Examining Consumption

Many adult Americans begin their day with a cup of coffee, but this morning ritual can have
significant environmental repercussions. In fact, many of our lifestyle choices consume
resources and affect the environment in ways that are hard to see.

Coffee is the most popular beverage in the world, but coffee beans cannot be grown just
anywhere. Crops do best in equatorial regions with consistent sunlight, and many varieties
require higher altitudes to thrive. As a result, a handful of regions with suitable conditions
are growing coffee for the entire world, and this can put a big strain on water and soil in
these environments. Coffee plants are also more productive when they are “sun cultivated”
rather than grown in natural, shaded environments, so many of these locations are cutting
down forests to maximize sunlight.

(continued)

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89

Section 3.6 Population Growth and Material Consumption

Close to Home: Examining Consumption (continued)

Even though growing regions are heavily impacted by global coffee consumption, they do not
always receive the majority of the benefits. On average, coffee growers receive about 10%
of coffee revenue (Blacksell, 2011), and many producers can barely meet their daily needs.
Low wages also encourage producers to grow coffee as cheaply and as quickly as possible,
without taking the long-term health of their environment into account.

As more consumers have become aware of these issues, the coffee industry has responded
with new products. Fair trade coffees try to ensure that growers get paid adequately for

their coffee beans, and more retailers
are offering shade-grown varieties
that can result in less environmental
destruction. Several organizations
now provide certifications to help
consumers identify these better
alternatives. The Smithsonian Bird
Friendly certification ensures that
forests are protected during coffee
production. The Rainforest Alliance
certification indicates that growing
practices and compensation both meet
strict sustainability standards. Fair
trade options might have a Fair Trade
USA symbol, and many organic options
are identified with the familiar USDA
stamp from the U.S. Department of
Agriculture.

Affluence is an important factor in determining how much coffee gets consumed and
how much environmental damage occurs as a result, but it also influences where these
environmental impacts occur. Compare the Worldmapper map on global coffee production
and the Worldmapper map on global coffee consumption. According to this data, who do
you think is enjoying the majority of the world’s coffee, and who do you think is suffering the
worst of its environmental impacts?

What is striking about these maps is that several of the largest coffee-producing regions are
not major consumers. Growers in places like Vietnam, Honduras, and Colombia have found
that their coffee harvests provide the greatest benefit when they are sold to consumers in
more affluent nations like the United States, Germany, and Japan. The places that consume
coffee often do not experience the environmental consequences. Meanwhile, less affluent
regions are taking on environmental burdens for economic gain.

Coffee is not the only form of consumption that has spatially removed consequences. Food,
clothing, electronics, and many other daily consumables have a good chance of affecting
environments in some other part of the world. It is important that we understand how these
production chains operate so that we can begin to develop better ways of meeting our daily
needs. Can you come up with any strategies for reducing the impacts of your consumption
patterns? Are you aware of any goods that are produced in more environmentally friendly
ways than others? Are there ways of keeping our environmental impacts a little closer to
home? Finally, are there ways you can consume less and still have the lifestyle you desire?

andresr/E+/Getty Images Plus
A coffee plantation in Colombia. Fair trade
coffee growers ensure that their workers are
paid adequately.

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90

Section 3.6 Population Growth and Material Consumption

The IPAT formula helps us consider and analyze the wide gap that exists in resource con-
sumption patterns between the wealthiest and the poorest people on the planet. For example,
it’s estimated that the world’s richest 500 million people, representing just 7% of the global
population, produce 50% of worldwide carbon dioxide pollution. In contrast, the poorest 50%
of the global population produce just 7% of worldwide carbon dioxide pollution. Meanwhile,
an average citizen of a country like the United States consumes nearly 40 times the amount
of energy that typical person in Bangladesh consumes. These kinds of statistics illustrate that
overpopulation may be less of a concern than overconsumption. What the IPAT formula really
helps us do is see how the factors of population, affluence, and technology interact and inter-
relate to determine the overall environmental impact of a given population.

Revisiting the Environmental Footprint
Recall from Chapter 1 that an environmental footprint is a measure of how much land and
water is required to produce the resources and absorb the waste products of a given person
or group of people. Environmental footprints can be calculated at the level of the individual,
family, business, university, city, state, or nation—or even the entire world. In one sense, the
environmental footprint measure is the outcome of the IPAT formula. By calculating the envi-
ronmental footprint for a specific country, we can see how the combination of population size,
affluence/consumption, and technology choices shape that country’s impact on the environ-
ment. And by looking at the differences in environmental footprints across countries, we can
gain a better idea of whether population or affluence/consumption is the biggest factor in
shaping the environmental footprint of that nation.

Global Footprint Network Approach
The Global Footprint Network (GFN) is a research organization that calculates and publishes
data on environmental footprints for different countries around the world. The GFN also
works to find ways for countries, organizations, and even individuals to reduce their envi-
ronmental footprints and have less of an impact on the environment. The GFN examines the
environmental footprint from both the demand side and the supply side. On the demand side,
the environmental footprint accounts for our consumption of plant-based food and fiber, live-
stock/animals, fish products, timber/forest products, space for buildings and infrastructure,
and the space needed to absorb our wastes, especially carbon dioxide emissions. On the sup-
ply side, biocapacity is a measure of the productivity of the land and resources available to
provide for human needs. In short, the environmental footprint measures the “demand for
nature” of a given population, while biocapacity measures the “supply of nature” available to
that population on a sustainable basis.

By comparing a population’s environmental footprint to its biocapacity, the GFN approach can
determine whether that group of people is running an ecological deficit or if the group still has
an ecological reserve. An ecological deficit occurs when a population consumes resources
and generates wastes at a rate that exceeds what its ecosystems can provide or absorb on a
sustainable basis. In contrast, an ecological reserve occurs when a population’s biocapacity
exceeds its footprint: The population is consuming resources and generating wastes at a rate
that is within what its ecosystems can provide or absorb on a sustainable basis.

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91

Section 3.6 Population Growth and Material Consumption

Recall from Chapter 1 that natural capital is both the resources and services provided by
nature. Also recall that sustainability is development that occurs in a way that does not
deplete or use up natural capital. Essentially then, when a nation or group of people has an
environmental footprint that exceeds its biocapacity—that is, when it is running an ecological
deficit—it has to either import natural capital from other places or liquidate its own natural
capital. In other words, measuring environmental footprints against biocapacity is one way to
determine whether a population is operating in a way that is sustainable.

Comparing Different Countries
There are multiple ways to compare environmental footprints between countries and popu-
lations, but comparing the average footprint of citizens of different countries will help us
examine how population size interacts with levels of affluence and consumption to determine
a country’s impact on the environment. Table 3.3 lists 25 different countries and the average
environmental footprint and biocapacity per person, the total environmental footprint and
biocapacity per country, the ecological deficit or reserve, and data on fertility rates, popula-
tion growth, and total population per country. Note that Table 3.3 lists the countries in order
of the size of their environmental footprint per person, starting with the smallest (Haiti). You
can also explore the Ecological Footprint Per Person map at the Global Footprint Network’s
Ecological Footprint Explorer.

Lee Lorenz/Cartoon Collections

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92

Section 3.6 Population Growth and Material Consumption

Table 3.3: Environmental footprint and population data for 25 countries

Country

Environ-
mental
footprint
(ha/
person)

Bio-
capacity
(ha/
person)

Total envi-
ronmental
footprint
(million ha)

Total bio-
capacity
(million
ha)

Ecological
deficit or
reserve
(million
ha) TFR

Popu-
lation
growth
rate

Total
popula-
tion
(millions)

World 2.75 1.63 20,509 12,169 –8,340 2.4 1.2 7,621.4

Haiti 0.68 0.32 7 4 –3 3.0 1.7 10.8

Bangladesh 0.84 0.41 137 66 –71 2.1 1.4 166.4

Zambia 0.95 1.88 16 31 15 5.2 3.1 17.7

Uganda 1.06 0.48 44 20 –24 5.4 3.2 44.1

Nepal 1.07 0.56 31 16 –15 2.3 1.4 29.7

India 1.17 0.43 1,547 566 –981 2.3 1.4 1,371.3

Tanzania 1.22 1.02 68 57 –11 5.2 3.3 59.1

Philippines 1.33 0.55 137 57 –80 2.7 1.5 107.0

Cuba 1.78 0.81 20 9 –11 1.6 0.2 11.1

El Salvador 2.06 0.6 13 4 –9 2.3 1.3 6.5

Vietnam 2.12 1.02 201 96 –105 2.1 0.9 94.7

Peru 2.24 3.68 71 117 46 2.4 1.4 32.2

Thailand 2.49 1.18 171 82 –89 1.5 0.2 66.2

Brazil 2.81 8.7 584 1,807 1,223 1.7 0.8 209.4

South
Africa

3.15 0.96 176 54 –122 2.4 1.2 57.7

China 3.62 0.96 5,195 1,374 –3,821 1.8 0.5 1,393.8

Malaysia 3.92 2.26 122 70 –52 1.9 1.1 32.5

Japan 4.49 0.58 574 74 –500 1.4 –0.3 126.5

Germany 4.84 1.62 397 133 –264 1.6 –0.2 82.8

Saudi
Arabia

6.23 0.42 201 14 –187 2.4 1.4 33.4

Australia 6.64 12.27 160 296 136 1.7 0.6 24.1

Denmark 6.8 4.17 39 23 –16 1.8 0.2 5.8

Canada 7.74 15.12 281 549 268 1.5 0.3 37.2

United
States

8.1 3.65 2,611 1,175 –1,436 1.8 0.3 328.0

Luxem-
bourg

12.91 1.24 7 0.7 –6 1.4 0.3 0.6

Sources: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content
/uploads/2018/08/2018_WPDS.pdf); “Ecological Footprint Explorer,” by Global Footprint Network, 2018 (http://data
.footprintnetwork.org/#/compareCountries).

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93

Section 3.6 Population Growth and Material Consumption

On average, across the entire world, each person has an environmental footprint of 2.75 hect-
ares (ha), or roughly 7 acres. In other words, each of the 7.7 billion people on the planet
needs an equivalent of about 7 acres to provide the resources he or she needs and absorb the
waste products he or she generates. However, this average masks significant variations in the
environmental footprint between nations and peoples. For example, in countries like Haiti,
Bangladesh, and Zambia, the environmental footprint per person is less than 1 hectare (2.47
acres). In contrast, in countries like Luxembourg, the United States, and Canada, the environ-
mental footprint per person is over 7 hectares (or 17.3 acres).

While there are reasons to be concerned, from an environmental standpoint, about coun-
tries like Tanzania, Zambia, and Uganda because of their high fertility and population growth
rates, their environmental footprints provide a somewhat different perspective. Based on the
environmental footprint data presented in Table 3.3, an average American uses the Earth’s
resources and natural capital at a rate that is 7 to 8 times greater than an average Zambian,
Ugandan, or Tanzanian. The environmental footprint concept allows us to broaden our focus
beyond just the absolute numbers of people in a given country and also to consider the
resource and material consumption patterns of the people in that country.

Table 3.3 also provides data on the average biocapacity available per person, as well as the
total environmental footprint and available biocapacity for each of the countries listed. Com-
paring the average environmental footprint to the average biocapacity, or a country’s total
environmental footprint to its available biocapacity, allows us to see which countries are
operating an ecological deficit.

Globally, the average environmental footprint is 2.75 hectares, whereas biocapacity is only
1.63 hectares. This suggests that we are running a global ecological deficit. Some of the coun-
tries with relatively low environmental footprints also have quite limited biocapacity. For
example, Haiti, the Philippines, India, and Cuba all have environmental footprints that are
less than 2 hectares per person, but in each case their average biocapacity per person is even
lower, suggesting that all these countries are running an ecological deficit. In contrast, some
of the countries with relatively high ecological footprints also have higher biocapacity. Aus-
tralia and Canada, in particular, both have footprints that are large but still lower than their
biocapacity, suggesting that they still have some ecological reserve. Both of these countries
have large land areas and relatively low populations, making them something of an exception
to the rule. You can also explore the Ecological Deficit/Reserve map at the Global Footprint
Network’s Ecological Footprint Explorer.

Learn More: Worldmapper

Typically, maps are used to show us where a city, state or country is located relative to other
locations. But at the website https://worldmapper.org/, maps are used to display information
about countries beyond just their physical location. Worldmapper does this by distorting the
size of a country to represent a characteristic of that country’s economy or population. For
example, the Close to Home: Examining Consumption feature references Worldmapper maps of
coffee consumption and production, which illustrate that coffee is consumed in different places
from where it is produced. Other maps related to the environment and the IPAT equation
include representations of carbon dioxide emissions, biodiversity hotspots, and human
development. Visit https://worldmapper.org and have a look at the world in a whole new way.

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94

Bringing It All Together

Global Consequences
The GFN estimates that over 80% of the world’s population lives in countries that are run-
ning ecological deficits. The GFN also estimates that the global ecological deficit is so bad that
at our current rates of consumption, waste generation, and natural capital usage, we would
require the equivalent of 1.7 Earths to meet our needs without running a deficit. Since we are
obviously not in a position to import resources or biocapacity from other planets, this can
only mean that we are liquidating natural capital faster than it can regenerate. This does not
meet the standard for sustainability, and it means that we are undermining our own future in
the process.

To call attention to this situation, the GFN established what it calls Earth Overshoot Day every
year. Earth Overshoot Day is the date each year when human consumption of natural capital
exceeds what’s available on a sustainable basis for that year. Ideally, humanity should use no
more than what it needs each year by December 31. In 2000 Earth Overshoot Day came in
late September, meaning humanity had used all of the resources and natural capital available
for 2000 on a sustainable basis by late September. Today our population and resource con-
sumption has grown so that Earth Overshoot Day now falls on August 1. Resource and natural
capital consumption that occurs from then until the end of the year represents natural capital
liquidation and a further move away from sustainability.

Bringing It All Together

Every environmental issue and topic that the remaining chapters of this book will cover is
affected in some way by population change and rates of resource and material consumption.
Global population has grown from under 1 billion in 1800 to over 7.7 billion today and is
projected to increase to around 11 billion by 2100. The addition of 10 billion more people
over a 300-year period has ushered in the Anthropocene, the age of humans. High rates of
material and resource consumption among the more affluent members of global society
have furthered the far-reaching impacts that humans are having on the global environment.

As the focus shifts in subsequent chapters to specific environmental issues and concerns,
keep in mind some of the key lessons from this chapter. First, despite dramatic declines in
fertility rates worldwide, human population growth continues apace. Second, it’s impor-
tant to consider levels of affluence and consumption, in addition to absolute numbers of
people, in assessing the overall environmental impact of a given population. Third, it will
take enormous progress in both slowing and stabilizing population as well as in reducing
resource and material consumption if we are to try to achieve sustainable development. At
present, in an ecological sense, we are living way beyond our means, and we are able to do
this only because we are consuming and depleting natural capital resources at rates that are
not sustainable. In essence, we are selling off our natural assets to maintain our current way
of life. This cannot go on forever. As we shift to a discussion of food, forests, water, oceans,
energy, and atmosphere, try to challenge yourself to think what you as an individual, and we
as a broader society, can do to shift to a more sustainable approach to resource and environ-
mental management.

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95

Bringing It All Together

Additional Resources

Demographics

There are a number of online sources that allow you to see how world population is chang-
ing every second of every day. The first two links listed below are basic population clocks,
while the third provides a more in-depth dashboard view of the data. Note that there are
slight discrepancies in the population clock numbers. Why do you think that might be? Dif-
ferent methods? Different assumptions? Different sources of data?

• https://www.census.gov/popclock/
• https://www.worldometers.info/world-population/
• https://www.unfpa.org/data/world-population-dashboard

You can find a lot of basic demographic data and other useful information about population
trends and issues at these websites.

• https://www.prb.org/
• https://www.un.org/en/development/desa/population/index.asp
• https://www.census.gov/topics/population.html

The Demographic Transition

This website provides an interactive lab/simulator that allows you to change the demo-
graphic characteristics (such as birth and death rates) of a sample population and see what
the resulting effects would be.

• http://www.learner.org/courses/envsci/interactives/demographics/demog.html

Population Policy and Fertility Control

There are many good TED Talks on the subject of population and the environment, but here
are three that are definitely worth watching, including one on Thailand’s “Mr. Condom.”

• Hans Rosling: Global Population Growth, Box by Box:

• Hans Rosling: The Good News of the Decade?:

• Mechai Viravaidya: How Mr. Condom Made Thailand a Better Place:

It’s been 25 years since the ICPD conference in Cairo, Egypt, but that event is still remem-
bered as a turning point in how the world viewed population growth and development. You
can learn more about the ICPD and what it accomplished at these sites.

• https://www.prb.org/whatwascairothepromiseandrealityoficpd
• https://www.unfpa.org/icpd

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96

Bringing It All Together

These links provide a good background on China’s one-child policy and how that policy has
recently begun to change.

• https://www.washingtonpost.com/world/asia_pacific/beijings-one-child-policy-is
-gone-but-many-chinese-are-still-reluctant-to-have-more/2019/05/02/c722e568
-604f-11e9-bf24-db4b9fb62aa2_story.html

• https://www.theguardian.com/world/2019/mar/02/china-population-control-two
-child-policy

The PBS series NOVA aired an interesting series called World in the Balance. The website for
this series has some interesting links, including a story about how government propaganda
was used to change minds about fertility and family planning in certain countries (“Popula-
tion Campaigns”) and how material consumption differs among families in different coun-
tries (“Material World”).

• https://www.pbs.org/wgbh/nova/worldbalance

The United Nations Population Fund published an interesting report that looks at future
population trends from the perspective of a 10-year-old girl.

• https://www.unfpa.org/sites/default/files/sowp/downloads/The_State_of_World
_Population_2016_-_English.pdf

Population Growth and Material Consumption

The Global Footprint Network, with the slogan “measure what you treasure,” is the go-to site
for all kinds of information on the environmental footprint concept, footprint data, and what
the world can do to bring its footprint in line with biocapacity.

• https://www.footprintnetwork.org

Key Terms
age-structure pyramid A graphical
illustration of how a specific population
is broken down by age and gender. Also
known as a population pyramid.

agricultural period The period in
human history that dates from about
10,000 years ago to about 200 years
ago. The domestication of plants and
animals, selective breeding of nutrient-rich
crops, and development of technologies
like irrigation and the plow greatly
increased the quantity and security of
food supplies for the human population.

crude birth rate (CBR) The number of
live births per 1,000 people in a given
population over the course of 1 year.

crude death rate (CDR) The number
of deaths per 1,000 people in a given
population over the course of 1 year.

demographic momentum The tendency
for a population to continue growing even
after its fertility rate declines, due to the
number of young people in the population.

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97

Bringing It All Together

demographic transition A model used by
demographers to explain and understand
the relationship between changing birth
rates, death rates, and total population.

demography The statistical study
of human population change.

ecological deficit A condition that occurs
when a population consumes resources
and generates wastes at a rate that exceeds
what its ecosystems can provide or absorb
on a sustainable basis; when a population’s
footprint exceeds its biocapacity.

ecological reserve A condition that occurs
when a population consumes resources and
generates wastes at a rate that is within
what its ecosystems can provide or absorb
on a sustainable basis; when a population’s
biocapacity exceeds its footprint.

emigration The act of people
moving out of a given population.

immigration The act of people
moving into a given population.

industrial period The period in human
history brought about by the introduction
of automatic machinery, starting
around the mid-18th century for some
countries and continuing into today.

IPAT formula An equation developed
by Paul Ehrlich and John Holdren that
illustrates that environmental impact
(I) is a function of population size (P),
average affluence (A) or consumption,
and choices in technology (T).

net migration rate The difference
between immigration and emigration
per 1,000 people in a given population
over the course of 1 year.

preagricultural period The period
in human history that dates from over
100,000 years ago to about 10,000 years
ago. During this time, humans developed
primitive cultures, tools, and skills and
slowly migrated out of Africa to settle
Europe, Asia, Australia, and the Americas.

rate of natural increase The rate of
population growth; in a given population,
birth rates minus death rates, excluding
immigration and emigration.

replacement rate The number of
children, or total fertility rate (TFR),
needed to “replace” the parents and
maintain a certain population.

total fertility rate (TFR) The
average number of children an
individual woman will have during
her childbearing years (currently
considered to range from age 15 to 49).

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4 Sustaining Our Agricultural Resources

branex/iStock/Getty Images Plus

Learning Outcomes

After reading this chapter, you should be able to

• Describe the origins and history of agriculture.
• Compare and contrast modern, industrialized agriculture with traditional agriculture.
• Explain what constitutes healthy soil and how it affects plant life.
• Describe the impact of chemical pesticides on the environment.
• Describe the impact of synthetic fertilizers on the environment.
• Describe the ways industrialized agriculture is dependent on water and fossil fuels.
• Analyze how animal production and concentrated animal feeding operations create

environmental problems.
• Describe how sustainable farming strategies differ from unsustainable ones.
• Evaluate the choices you can make to promote sustainable agriculture practices.
• Outline some high-tech, sustainable farming techniques.
• Describe the arguments for and against genetically modified organisms.

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100

Section 4.1 The Origins and History of Agriculture

In October 2018 the scientific journal Nature published a major research report that pre-
sented a troubling picture of the future of food, agriculture, and the environment (Spring-
mann et al., 2018). The authors of the report—including scientists from the United States,
Europe, and Australia—argue that, based on current trends, we will see an increase of 50% to
90% in the negative environmental impacts of food production by the year 2050.

Their prediction is based on three key factors. First, as presented in Chapter 3, global popu-
lation is expected to increase from roughly 7.7 billion people today to almost 10 billion by
2050. Second, the demand for food is actually growing faster than the population is, as ris-
ing incomes in countries like China result in more demand for meat and other animal pro-
teins, which require more resources to produce. And third, current agricultural practices are
already a significant contributor to major environmental problems like deforestation, air and
water pollution, and global climate change.

The Nature report used the planetary boundaries concept described in Chapter 2 to argue
that we need to change the way we produce, distribute, and consume food if we are to feed
10 billion people and not ravage the environment. We already use half of Earth’s ice-free
land surface for grazing livestock and growing crops to feed animals, and 77% of the Earth’s
land surface has already been developed or modified by human activities, up from just 15%
a century ago. Every year, more and more forests, including biodiversity-rich tropical rain
forests, are cleared for agriculture. Agriculture uses roughly 70% of global freshwater sup-
plies. Meanwhile, roughly one third of global food production ends up being discarded as
waste each year. This last fact is especially troubling, given that roughly 3 billion people are
malnourished and that 1 billion suffer from outright food scarcity and shortages.

Given these trends, and given the fact that agriculture and food production are essential
human activities, the Nature report focuses on the need to reduce the environmental impact
of current agricultural practices. This chapter will contrast the unsustainable approaches
to agriculture, which currently dominate, with sustainable approaches that we will need to
adopt in the decades ahead. It starts with a brief review of the origins and history of agricul-
ture and how it has shaped human history through time. This is followed by a review of the
basics of soil, climate, and plant growth. We then examine how current agricultural practices
are affecting the environment and why these practices are not sustainable. This is followed
by a discussion of sustainable agricultural practices, including ideas presented in the Nature
report, designed to help us stay within key planetary boundaries. Finally, the chapter will
explore the somewhat controversial issue of genetic engineering and genetically modified
organisms.

4.1 The Origins and History of Agriculture

As discussed in Chapter 3, most of human history occurred during what could be called the
preagricultural period. Modern humans, or Homo sapiens, have been in existence for roughly
250,000 years, and for 95% of that period, they relied mainly on hunting and gathering to
meet their needs for food and sustenance.

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101

Section 4.1 The Origins and History of Agriculture

The Beginnings of Agriculture
Beginning about 10,000 years ago, however, human societies started to develop and rely
on agriculture to meet their needs for food and sustenance. Agriculture is an approach to
land management designed to grow domesticated plants and raise domesticated animals
for food, fuel, and fiber. Anthropologists believe that this transition from hunter-gatherer to
crop domestication and cultivation occurred for a couple of reasons. First, the climate was
going through a natural warming cycle after a period of glaciation, and warmer and wetter
conditions were more conducive to agriculture. Second, population growth among hunter–
gatherer communities may have reached a point at which wild food sources were becoming
scarce. Crop domestication and agriculture allowed these communities to grow more food on
a given amount of land, and the first crops that were domesticated were easy to grow, dry, and
store. Early agriculturists also began to settle in specific locations and to domesticate animals
like dogs, goats, sheep, and pigs. Eventually, these more settled communities grew into small
villages and even cities, and over the next 8,000 years, the human population of the planet
grew from a few million to hundreds of millions of people.

Beyond crop selection and plant and animal domestication, other developments and tech-
nological advances helped increase agricultural productivity over time. The domestication
of cattle was soon followed by the invention of the plow, allowing early farmers to cultivate
more land using less human energy. Evidence of irrigation—the deliberate diversion of
water to crops—dates back at least 5,000 years, and this helped expand the area under culti-
vation. Improvements in metal production, crop storage, and transportation also contributed
to increased agricultural productivity over thousands of years.

Despite these developments, however, agriculture in the year 1500, 1600, or 1700 would
have looked similar to what was being practiced 2,000 to 3,000 years before that. Increased
land under cultivation allowed for more food production and population growth, but these
increases occurred slowly over centuries and millennia.

The Modernization of Agriculture
That situation began to change around the begin-
ning of the industrial period, roughly 200 years
ago. The world population was hitting the 1 billion
mark, and the Reverend Thomas Malthus argued
that human population was growing faster than
food production. The result, Malthus predicted,
would be increasing starvation, famine, and dis-
ease, as well as social collapse, as human num-
bers outstripped food supply. However, despite
some devastating famines in places like Ireland
and India, food production was generally able to
keep up with a growing population. New lands
that had been colonized were put into agricultural
production (especially in the Americas), and the
invention of agricultural machinery made farming
more efficient.

summersetretrievers/iStock/Getty Images Plus
Early farming machines, such as the
steam-driven thresher pictured here,
changed agricultural practices during
the Industrial Revolution.

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102

Section 4.1 The Origins and History of Agriculture

At the same time, scientific advances in fields like chemistry, plant genetics, and soil science
boosted crop productivity per unit of land. In particular, breakthroughs in the production of
synthetic fertilizer in the late 19th century, especially in the production of nitrogen fertilizer
on an industrial scale, enabled continued increases in food production. Fertilizers are sub-
stances that add nutrients to the soil, thereby encouraging plant growth. While traditional
farmers had long made use of available organic material for fertilizer, it’s estimated that with-
out the development, mass production, and use of synthetic nitrogen fertilizers, the world’s
population would never have exceeded 4 billion (Smil, 1997).

The Green Revolution
By the 1960s world population had reached 3 billion people, and another 1 billion were being
added every 12 to 14 years. Massive famines in China, sub-Saharan Africa, and southern Asia
claimed millions of lives and led to a return of Malthusian thinking about population and food
security, whereby everyone has access to an adequate and reliable food supply. It was at this
time that ecologist Paul Ehrlich published The Population Bomb, warning of mass starvation
and upheaval due to human population growth. However, a series of advances in agricultural
production that came to be known as the Green Revolution also occurred.

The Green Revolution was not the result of a single scientific breakthrough or technological
development but rather the collective result of a number of changes in the way humans grew
food. Plant breeders developed new, high-yielding varieties of wheat, rice, and corn that pro-
duced as much as four times the amount of grain per acre as conventional varieties. Expanded
use of irrigation systems, synthetic fertilizer, and chemical herbicides and pesticides allowed
farmers to grow even more crops on the same fields. The results of these changes were dra-
matic. From 1960 to 2014 global production of the five main cereal crops—corn, rice, wheat,
barley, and sorghum—increased by an estimated 280% and yields by an estimated 175%,
while the land area devoted to cereal production increased by only 16% (Ritchie, 2017).

The Challenges of Today
Today we may need another Green Revolution to keep up with continued population growth,
changes in diet, and the environmental impacts of modern, industrialized approaches to agri-
culture. The impressive increases in yield achieved in the first few decades of the Green Revo-
lution have begun to level off. At the same time, we continue to add roughly 75 million new
people to the planet each year. Perhaps more importantly, many of the agricultural practices
that emerged during the Green Revolution—including the heavy use of irrigation, synthetic
fertilizers, and chemical pesticides—are taking a severe toll on the environment.

Rapid advances in science and technology have allowed us to feed a population that has
grown from 1 billion to over 7.7 billion in just 200 years. However, there is overwhelming
evidence that our current approaches to feeding the world are pushing us close to or beyond
planetary boundaries and environmental limits. Clearly, feeding the world as human popula-
tion reaches 8, 9, or 10 billion will require a change if we are to once again avoid the worst
Malthusian predictions of the past.

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103

Section 4.2 Characteristics of Industrial Agriculture

4.2 Characteristics of Industrial Agriculture

The Green Revolution ushered in what is now known as industrial agriculture. These indus-
trialized approaches have enabled food production to keep pace with population growth, but
they differ in fundamental ways from the traditional farming practices that were in place
for almost 10,000 years. To better understand the environmental impacts of industrialized
agriculture and identify more sustainable alternatives to farming, it’s instructive to com-
pare industrial agriculture with what is known as traditional agriculture. Agriculture is a
necessary part of human civilization, and the challenge will be to combine the technological
advances of industrialized agriculture with the sustainable practices of traditional agricul-
ture to feed a growing human population.

Linear
First, whereas traditional agricultural practices are based on cyclical systems common in
nature, industrial farming is highly linear and modeled on industrial systems. Industrial agri-
culture is sometimes referred to as “factory farming” because it is focused mainly on inputs
(pesticides, fertilizers, seeds, water) and outputs (corn, wheat, soybeans, meat). The primary
goals are to increase production and yield while decreasing costs of production.

A traditional farm will likely raise a variety
of crops and be home to animals like horses,
cows, pigs, chickens, goats, and so on. These
animals’ waste products in the form of
manure are used as fertilizer on crops, some
of those crops are fed to animals, and the
cycle begins again.

In contrast, an industrial farm will likely
focus on raising a single crop. The farmers
“import”—rather than generate on their
own farms—seeds, fertilizers, pesticides,
herbicides, water, and energy for equipment
to grow that crop. In the United States and
other developed countries, much of the pro-
duction from these types of farms is soy and
corn that is then fed to animals (mainly cows, chickens, and pigs). The animals are then fed to
people, and waste products from both the animal production facilities and people are treated
in sewage treatment facilities before finally ending up in water bodies (in the case of liquids)
or landfills (in the case of solids). After that, the farmer goes back and “imports” a whole new
set of inputs to start the process all over again.

Designed to Maximize Output
Second, whereas traditional agriculture focuses on the production of a wide variety of crops,
animals, and other products, industrialized farming is designed to maximize the output of a
narrow range of crops.

fotokostic/iStock/Getty Images Plus
While traditional farms grow a variety of
crops, industrial farms almost always raise one
single crop.

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Section 4.2 Characteristics of Industrial Agriculture

A diversity of crops and animals, sometimes referred to as polyculture farming, better
assures the farm family of meeting its needs. At the same time, as will be discussed later in
the chapter, this diversity mimics natural systems and is thus better for the environment.
Traditional farming also generally includes the management of some trees, a practice known
as agroforestry. Trees provide fuel, fruit, nuts, building material, and help with on-farm water
retention and management.

In contrast, nearly all large-scale agriculture today is based on planting a single crop over
large areas of land to maximize productivity. Whereas in the past a typical farm might pro-
duce as many as 10 different agricultural products for market, today a farm is more likely to
grow a single crop like corn or soybeans. Agricultural mechanization combined with heavy
inputs of agricultural chemicals allows a single farmer to grow the same crop on thousands
of acres of land, something that would have been unimaginable just a few generations ago.

This kind of agriculture, known as monoculture farming, raises a number of concerns. The
overreliance on a small number of genetically similar crop varieties increases the risk that a
widespread insect infestation, crop disease, or fungal infection could wipe out a major global
food source. In addition, large-scale monoculture farming tends to reduce the number of
farmers and farm families living in rural areas. Some observers have associated this phenom-
enon with the loss of community and economic diversity in these areas (Union of Concerned
Scientists, 2019).

Reliant on External Inputs
Finally, whereas traditional agriculture tends to be self-sustaining, industrialized farming is
heavily reliant on external inputs to survive. Today’s industrial farmers depend on chemical
pesticides and herbicides to control insects and weeds and must apply increasing amounts of
synthetic fertilizers to maintain crop yields. Industrial farmers also require large amounts of
water and fossil fuel energy resources. The environmental impact of these realities will be the
focus of much of this chapter, and the chapter will also explore how ideas and practices from
traditional agriculture can be incorporated into modern farming to make it more sustainable.
Table 4.1 offers a brief comparison of industrial and traditional agriculture.

Table 4.1: Industrial vs. traditional agriculture

Industrial Traditional

Focuses on maximizing yield (monoculture) Focuses on a diversity of species and products
(polyculture)

Results in higher rates of soil erosion and land
degradation

Maintains soil quality and long-term soil health

Relies on synthetic fertilizers and chemical
pesticides

Relies on organic fertilizers and natural approaches
to pest management

Requires heavy use of irrigated water Minimizes water use by matching crops to regional
climate

Heavily uses fossil fuels Uses minimal fossil fuels

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105

Section 4.3 The Importance of Soil

4.3 The Importance of Soil

When most people think of the term soil, they automatically think dirt. And for most people,
dirt is considered useless and something to be avoided whenever possible. In reality, soil is
much more than dirt, and it is soil that forms the foundation of virtually all land-based food
production around the world. Because soil health is so critical to agriculture, sustainable agri-
culture almost always implies sustainable management of soils. Traditional farming practices
tend to carefully manage soil fertility to ensure the ability to grow crops year after year. How-
ever, industrialized farming tends to depend on inputs of synthetic fertilizers to compensate
for declining soil quality.

What Is Soil?
Soil generally consists of five components:

1. mineral matter (sand, gravel, silt, and clay)
2. dead organic material (e.g., decaying leaves and plant matter)
3. soil fauna and flora (living bacteria, worms, fungi, and insects)
4. water
5. air

Variations in the levels of these components lead to many different types of soils and soil
conditions. Soils that are sandy drain quickly, whereas soils with high clay content hold water
and become sticky. Soils with high levels of organic matter tend to be soft and good for plants,
whereas compacted soils with few air spaces are less conducive to plant growth. High levels
of soil fauna and flora are also generally better able to support plant growth, since these liv-
ing organisms help decompose dead organic matter and make nutrients available to plants.

Most people are surprised that there can be so many living organisms in soil. Far from being
lifeless dirt, a small handful of soil can contain millions of bacteria and thousands of fungi
and algae (Ingham, 2019). Soils are also habitat for earthworms, ants, mites, sow bugs, centi-
pedes, and other decomposers that make nutrients available to plants.

Because soils consist of both living organisms and nonliving material that interact to form
a more complex whole, they meet the definition of an ecosystem. When we think of soils as
ecosystems in and of themselves, we can begin to see why many of the agricultural practices
discussed later in the chapter are not sustainable. Soil compaction from heavy farm machin-
ery, regular plowing and manipulation of soils, heavy applications of synthetic fertilizers and
chemical herbicides and pesticides, and overuse of irrigation all undermine long-term soil
health and threaten the future of agriculture.

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106

Section 4.3 The Importance of Soil

How Is Soil Made?
New soils can form over time and thus might be considered a renewable resource. However,
because soil formation is such a slow process, it might be better to think of soils as a finite,
limited resource. Soil formation occurs primarily as a result of two basic processes: weather-
ing and the deposition and decomposition of organic matter such as leaves.

Weathering is the process of larger rocks being worn away or broken down into smaller par-
ticles by physical, chemical, and biological forces. Physical weathering occurs through wind,
rain, and the expansion and contraction of rocks due to changes in temperature. Chemical
weathering is caused when water, gases, or other substances chemically interact with larger
rocks and break them apart. Biological weathering is caused by living organisms, such as
when tree roots grow and grind against rocks.

The deposition and decomposition of organic matter occurs when living organisms drop
waste or debris or die. When animals deposit waste or when plants shed leaves and branches,
this organic material gets added to the soil. Likewise, when plants, animals, and other living
organisms die and drop to the ground, decomposers and detritivores break them down and
incorporate that organic material into the soil.

The processes of weathering and deposition and decomposition are influenced mainly by
climate, topography, and time, allowing soils to form faster in some locations than in others.
For example, an inch of new soil can take 50 to 100 years to develop in a healthy grassland
ecosystem, whereas the same inch of soil might take 100,000 years to develop in a desert or
tundra ecosystem.

Soil scientists recognize that soil develops into distinct layers, and they refer to each of these
layers as a soil horizon. For our purposes, we can consider five different soil horizons: O, A,
B, C, and D. The O (organic) horizon is at the very top and is made up of decomposing plant
matter and animal waste that is sometimes referred to as humus. Below this is the A horizon,
which is made up of organic matter and mineral particles.

The A horizon is where most of the living soil organisms reside, and the upper portions of
the A horizon are generally referred to as topsoil. Most plant roots are established in the A
horizon, which is why soil health is often based on the condition of topsoil.

Below the A horizon is the B horizon, also known as subsoil, and below that is the C horizon,
which consists of weathered rock. Finally, the D horizon is known as bedrock (see Figure 4.1).

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107

Section 4.3 The Importance of Soil

Figure 4.1: Soil horizons

Farmers are most concerned with the fertility of the topsoil, or A horizon.

IkonStudio/iStock/Getty Images Plus

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108

Section 4.4 The Problem of Chemical Pesticides

Soil and Plant Life
Soil conditions have a lot to do with their ability to support plant life and agriculture, and the
term soil fertility defines those conditions. Among the most important factors influencing
soil fertility are nutrient levels, soil pH (a measure of the acidity or alkalinity of soil), and soil
structure.

We know from Chapter 2 that nutrients like phosphorous and nitrogen can be limiting factors
in plant growth. The amount of these and other nutrients in soils is dependent in part on the
amount of organic material that is deposited and decomposed in that area. This is why the
living organisms (e.g., bacteria, fungi, worms) that are found in soil—and act as decompos-
ers—are so important to soil fertility.

Soil pH is determined by many factors, including the amount of organic material added to
soils, the mineral composition of soil particles, and temperature and precipitation levels in
that area. Some plants thrive in more acidic soils, whereas others do better in soils that are
less acidic or even alkaline. Farmers utilize different soil additives to make soils more or less
acidic, depending on the type of crops they want to grow.

Lastly, soil structure refers to how much air is in the soil or how compact it is. Plant roots
and the living soil fauna and flora that improve soil fertility need oxygen and other gases
to survive, so well-aerated soils tend to be better for plant growth. In contrast, when soils
are compacted or compressed, such as through repeated pressure from tractors and heavy
farm equipment, they tend to become less aerated and less conducive to plant growth. Highly
compacted soils also decrease the ability of water to infiltrate and enter the ground, and as
this water runs off the surface, it can carry soil with it. The displacement of this valuable
resource—often caused by water or wind—is known as soil erosion.

4.4 The Problem of Chemical Pesticides

For as long as humans have farmed, they have had to contend with crop damage and compe-
tition from insects, fungus, and weeds. Early agriculturists made some use of chemicals like
sulfur—as well as salt, smoke, and other deterrents—to ward off pests, but for the most part,
traditional farming relied on more passive approaches to minimize crop loss. For example,
by growing a variety of crops and rotating where those crops are grown on the farm, tra-
ditional agriculturists created conditions that were not as favorable for the outbreak and
growth of pest populations. Likewise, traditional polyculture farming tends to promote and
provide habitat for pest predators like spiders, beetles, predatory mites, and mantids like
the praying mantis that feed on pests that can damage crops.

On the other hand, monoculture farming creates ideal conditions for pest and weed infesta-
tions. Because most insect pests are crop specific, and because monoculture farming grows
the same crop season after season over large areas of land, insect pests are able to establish
and spread in large numbers.

Agricultural pests are organisms that damage or consume crops intended for human use.
Agricultural weeds are plants that compete with crops. Of course, weeds and pests don’t

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109

Section 4.4 The Problem of Chemical Pesticides

necessarily see it this way, because they are
living organisms attempting to survive. Nev-
ertheless, weeds compete with agricultural
crops for sunlight, water, and nutrients, and
pests can damage or destroy plant roots,
stems, leaves, flowers, and fruit. As a result,
industrialized agriculture makes use of a
wide variety and a large quantity of chemi-
cals to control weeds and pests. Insecticides
kill insects, and herbicides kill weeds. There
are also fungicides that kill fungus, as well as
rodenticides that kill rodents. These chemi-
cals are collectively known as pesticides.

The agricultural chemical industry has
developed thousands of pesticides in the past 50 to 60 years, and it’s estimated that we apply
close to 454 million kilograms (1 billion pounds) of pesticides in the United States each year
(Alavanja, 2009). Roughly 80% of this pesticide is applied to farm fields, with the other 20%
applied to backyard lawns, gardens, golf courses, and parks. It’s also estimated that over 95%
of all corn and soybean crops planted in the United States are treated with herbicides each
year (Wechsler & Fernandez-Cornejo, 2016), whereas cotton is probably the most intensive
user of chemical insecticides (Cubie, 2006).

Biomagnification
One of the earliest chemical pesticides to come into widespread use was a compound known
as dichloro-diphenyl-trichloroethane, or DDT. First developed in the late 1930s, DDT was seen
to be an inexpensive, stable, and highly effective insecticide that was also relatively nontoxic
to humans and other mammals. Because DDT was a broad-spectrum insecticide, meaning it
could kill a wide variety of insects, it quickly became popular among farmers for controlling
crop pests, as well as mosquitoes and household insect pests.

After more than a decade of widespread use, however, in the 1950s it began to become appar-
ent that DDT might be causing unintended environmental consequences. Because DDT is a
long-lived and stable compound, it gradually built up in soils and water bodies. Because DDT
is fat soluble and attaches itself to body fats when ingested, it was also building up in popula-
tions of wild fish, birds, reptiles, and other organisms.

This poses a particular problem for animals near the top of the food chain. For example, DDT
sprayed on agricultural fields will eventually flow into streams or lakes, where it could be
ingested by tiny zooplankton. These organisms are then eaten by small fish, thereby accu-
mulating all the DDT in the zooplankton. Small fish are then eaten by larger fish that are then
eaten by birds of prey, like falcons, bald eagles, and pelicans.

Recall from Chapter 2 that only about 10% of the energy consumed at one trophic level is
available to the next level. This means that birds of prey, like the bald eagle, have to eat a lot
of fish to have sufficient energy. As birds eat, the DDT in fish becomes more and more concen-
trated in the birds.

fotokostic/iStock/Getty Images Plus
Industrial agriculture relies heavily on
pesticides to ward off pests.

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110

Section 4.4 The Problem of Chemical Pesticides

The increasing concentration of a chemical pesticide at higher levels of the food chain is
known as biomagnification. By the late 1950s and early 1960s, populations of birds of prey
were declining dramatically, and the cause was linked to high concentrations of DDT. It turns
out that DDT was not killing the birds outright but rather altering the way calcium was metab-
olized in their bodies. This resulted in a thinning of bird eggshells and low survival rates
for chicks. The 1962 publication of the book Silent Spring by ecologist Rachel Carson drew
attention to this unfolding disaster and eventually helped lead to the banning of DDT in most
developed countries.

Resistance
Today the agricultural chemical industry has learned some lessons from the experience with
DDT. Newer varieties of pesticides are designed to be short lived and less stable in the envi-
ronment so that they break down quickly after use. They are also designed to be more tar-
geted at specific species and applied at specific times when target pests are most vulnerable.
Nevertheless, a number of other environmental problems still remain with widespread pes-
ticide use.

First, because insects breed rapidly, they can develop genetic resistance to insecticides within
a relatively short time. In other words, the insecticide will wipe out most of the pests ini-
tially—but the ones that survived will multiply, and the insecticide will become less effective
with each successive generation (see Figure 4.2). Likewise, weeds can also develop resistance
to herbicides over time. Heavy applications of chemical pesticides will initially help control
insects and weeds, but over time they prove less and less effective as these organisms develop
a resistance.

It’s estimated that since the start of widespread chemical pesticide use in the late 1940s, over
500 species of insects (Gut, Schilder, Isaacs, & McManus, 2015) and 500 species of weeds
(Heap, 2019) have developed chemical resistance, prompting what is known as pest resur-
gence. Farmers are then forced into what some call a “pesticide treadmill” or a “pesticide
arms race” and must spend money on either larger doses of pesticides or new varieties of the
chemicals. And despite the fact that synthetic pesticide use has seen a 50-fold increase since
1950 and that today’s pesticides are 10 to 100 times more toxic to pests than those used in
the past (Roser & Ritchie, n.d.; Gross, 2019), it’s estimated that we still lose over 40% of major
crops to pests and crop diseases each year—a higher proportion than in 1950 (Elliott, 2015;
Fernandez-Cornejo et al., 2014).

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111

Section 4.4 The Problem of Chemical Pesticides

Figure 4.2: Pesticide resistance

Pests can develop resistance to pesticides over time. In this figure, the red bugs are the resistant
individuals. Notice how, with each subsequent generation, the number of resistant pests increase.
Eventually, the entire population will be resistant.

Based on “Managing the Community of Pests and Beneficials,” by L.Gut, A. Schilder, R. Isaacs, and P. McManus, in J. Landis and J. Sanchez
(Eds.), Fruit Crop Ecology and Management, 2002, East Lansing, MI: Michigan State University.

First generation Second generation

Pesticide
application

After pesticide
application

Pesticide
application

Pests
reproduce

After pesticide
application

Time

P
e
s
t

p
o

p
u

la
ti

o
n

Pesticide
application

Pesticide
application

Pesticide
application

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112

Section 4.4 The Problem of Chemical Pesticides

Threat to Biodiversity
Another major environmental problem
associated with the widespread use of
chemical pesticides in agriculture is the
impact these chemicals have on nontarget
species and biodiversity. The case of DDT
and its impact on birds like the bald eagle
was an early and high-profile example of
this problem. Today there continue to be
concerns over the impact of pesticides on
natural predators, other wildlife, and bio-
diversity generally, even if it doesn’t involve
a species as well known as the bald eagle.
Some of the nontarget species whose popu-
lations are reduced or eliminated by chemi-
cal insecticides include the spiders, beetles,
and mantids that help control insect pests
in traditional agricultural systems.

One particular area of concern involves the impacts that some pesticides appear to be hav-
ing on bee colonies around the world. A newer class of chemical compounds developed in
the 1990s known as neonicotinoid pesticides are now the most widely used form of insec-
ticides globally. These chemicals appear to be responsible for significant declines in honey-
bee populations in agricultural regions and for the complete collapse of honeybee colonies
through a process known as “colony collapse disorder.” This development is a significant
concern because honeybees provide a critical ecosystem function by pollinating many major
vegetable and fruit crops, including tomatoes, peppers, apples, and almonds. In addition to
impacting honeybees, neonicotinoid pesticides appear to be negatively affecting a variety of
bird and fish species as well.

Threat to Human Health
Lastly, chemical pesticides can pose a threat to human health. The World Health Organization
(WHO) estimates that every year, at least 3 million agricultural workers are directly poisoned
through improper handling of and exposure to chemical pesticides, which results in over
250,000 deaths a year (WHO, n.d.a). Every year, the Environmental Working Group (EWG)
publishes a Shopper’s Guide to Pesticides in Produce, which estimates levels of pesticide
residues found on fruits and vegetables sold in grocery stores around the United States. The
2019 EWG list ranked strawberries, spinach, kale, nectarines, apples, grapes, peaches, cher-
ries, pears, tomatoes, celery, and potatoes as the “dirty dozen” in terms of levels of pesticide
residues (EWG, 2019a). While the link between exposure to pesticide residues from food and
cancer or other health problems is complicated, a number of studies suggest that people with
less exposure have fewer of these problems (Baudry et al., 2018; Chiu et al., 2018).

It’s also estimated that well over 90% of chemical pesticides sprayed on crops never reach the
target insects they were intended for (Duke, 2017). Instead, they drift through the air, run off
into streams and lakes, or seep into groundwater—water found underground in soil or in the

iStock/Thinkstock
Pesticides can harm nontarget species, such
as the praying mantis, reducing their numbers
and creating unforeseen environmental
consequences.

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113

Section 4.5 The Problem of Synthetic Fertilizers and Poor Soil Management

pores and crevices of rock. These chemicals can then be inhaled by people or ingested through
drinking water. Agricultural chemicals like glyphosate (trade name Roundup), malathion, and
atrazine have been found in municipal water supplies and in private wells, especially in heav-
ily agricultural areas. These and other chemicals have been linked to human health problems
such as infertility, low sperm count, and prostate and testicular cancers.

Overall, chemical pesticides have become a virtual necessity in industrialized agriculture
because of the perfect conditions created for pests and weeds in monoculture farming. How-
ever, the heavy use of these chemicals is proving less effective over time as insect pests and
weeds develop greater resistance to them. Furthermore, herbicides and pesticides are having
negative impacts on nontarget species of animals and are also implicated in a variety of nega-
tive human health impacts.

Learn More: Shopping for Produce

You can learn more about the EWG’s Shopper’s Guide to Pesticides in Produce, and what you
can do to reduce pesticide exposure in your own life, here.

• https://www.ewg.org/foodnews

4.5 The Problem of Synthetic Fertilizers and Poor
Soil Management

Just as industrialized, monoculture farming requires chemical pesticides, it also relies on
synthetic fertilizers. Raising the same crop year after year quickly depletes soils of specific
nutrients and requires the application of synthetic fertilizers to maintain crop yields. Tra-
ditional farmers use substances already produced on their farms, applying animal manure
or compost or plowing under old crops to enhance soil fertility. In contrast, industrialized
farmers apply over 109 million metric tons of synthetic nitrogen fertilizer alone to crop
fields each year (Pearce, 2018b). This dependence on synthetic fertilizers is a symptom of
the linear approach to agriculture, which views soil as simply one input to the production
process, rather than the complex, living ecosystem that it actually represents. Heavy fertil-
izer use and poor soil management can result in serious environmental problems, including
pollution of groundwater supplies, nutrient runoff and eutrophication, and soil erosion and
land degradation.

Water Pollution
Industrialized farming operations tend to spray more chemical pesticides than needed and
also tend to apply more fertilizer than plants can make use of. This excess nitrogen fertilizer
in the form of nitrate can make its way through soils and into groundwater deposits. This
nitrate pollution can persist in the water supply and build up over time as more and more
nitrogen fertilizer gets applied to farm fields. While nitrate pollution in groundwater is not a

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114

Section 4.5 The Problem of Synthetic Fertilizers and Poor Soil Management

major health threat for adults, it can cause low oxygen levels in the blood of infants and chil-
dren and result in a potentially fatal condition known as “blue baby syndrome.” Large areas
of the agricultural Midwest, including much of Iowa, Nebraska, and Kansas, have both high
levels of nitrogen fertilizer application and vulnerable aquifers that provide drinking water
to the general population. As a result, many of these areas are at high risk of groundwater
contamination by nitrate.

In addition to groundwater pollution, excess fertilizer from farms can contribute to the pollu-
tion problem known as eutrophication (recall the case study in Section 2.4). Excess nitrogen
and phosphorous fertilizers run off of farm fields (as well as residential lawns, golf courses,
and parks) into bodies of water, where they fertilize aquatic plant growth and create algae
blooms. This aquatic plant life, or phytoplankton, builds up and eventually sinks to the bot-
tom, where it is decomposed by bacteria that use up the dissolved oxygen in the water. This
results in low oxygen or hypoxic conditions that can lead to the death and displacement of
fish and other aquatic life and eventually to the formation of low oxygen areas known as dead
zones. As we learned in Section 2.4, the Gulf of Mexico dead zone is the largest such area in the
United States, and the formation of this dead zone is linked directly to the large quantities of
nitrogen and phosphorous flowing from the agricultural Midwest into the Gulf.

Topsoil Erosion
While some soil erosion occurs naturally, industrialized agricultural practices greatly speed
up this process.

Water is the primary cause of soil erosion from most farm fields. Because most forms of
industrialized agriculture involve plowing and clearing the land of vegetation, even small
amounts of rain can move soil particles off a field, since there are no roots or organic material
to hold them in place. Mechanization and the use of heavy farm equipment compacts soils and
requires more frequent plowing and manipulation of soils, which can worsen erosion and fur-
ther deplete the soil of nutrients. This type of gradual, almost imperceptible loss of topsoil is
known as sheet erosion. Heavier rains can create small streams of water or rivulets that wash
even greater amounts of soil off fields in a process known as rill erosion. In more extreme
cases these small streams of water can merge to form large streams that can gouge out large
channels from fields in a process known as gully erosion. Soil erosion not only reduces soil
fertility and crop productivity, it also creates water pollution and sedimentation problems in
rivers, streams, and lakes.

Lucagal/iStock/Getty Images Plus NeilBradfield/iStock/Getty Images Plus Adnan Cetin/iStock/Getty Images Plus
There are different types of soil erosion: sheet (left), rill (center), and gully (right).

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115

Section 4.6 The Dependence on Water and Nonrenewable Energy

In addition to water, heavy winds can loosen and blow topsoil off farm fields, especially in
places that are dry and flat. The 1930s Dust Bowl in prairie areas of the United States and
Canada was a result of drought conditions and removal of trees and other ground cover to
expand farm area. While not as dramatic as images from the 1930s, windblown soil erosion
continues to be a major problem in the United States today, and scientists cannot rule out
the return of dust bowl conditions in periods of severe drought. In drier regions of Asia and
Africa, overgrazing of livestock and clearance of vegetation is allowing desert areas to expand
in a process known as desertification. Over the past 3 decades, China has lost a land area the
size of Indiana to desertification as the Gobi Desert encroaches into areas that were previ-
ously suitable for some forms of agriculture.

Air Pollution and Climate Change
Excessive use of nitrogen fertilizer can also contribute to air pollution. Ammonia gas from
nitrogen fertilizer application can contribute to haze great distances from where the fertil-
izer is being applied. Nitrous oxide gas can also form in soils fertilized with nitrogen fer-
tilizer. Nitrous oxide is a local/regional air pollutant and also contributes to global climate
change and even ozone depletion (discussed in Chapter 8). It’s estimated that two thirds of
global nitrous oxide emissions from human activities are a result of agriculture. Ammonia
and nitrous oxide can react with other compounds in the atmosphere to form fine particulate
pollution. These particulates are responsible for haze and are also a public health risk when
inhaled into the lungs. Wind erosion of farmlands can carry soil particles into the air and also
contribute to particulate pollution.

Overall, heavy application of agricultural fertilizers and poor soil management practices are
resulting in the degradation of two key forms of natural capital: water and soil. Excess fertil-
izer can seep into groundwater or run off into surface water and result in drinking water pol-
lution, eutrophication, and aquatic dead zones. Soil erosion by water and wind can reduce soil
quality and contribute directly to water pollution.

4.6 The Dependence on Water and Nonrenewable Energy

Unlike traditional agricultural systems that make relatively limited use of external inputs
and are powered primarily by energy from the sun (photosynthesis), modern industrialized
agriculture is heavily reliant on external inputs of water and fossil fuel energy resources.
Traditional agricultural systems and approaches are generally tailored to local conditions.
For example, farmers in regions with less precipitation and more frequent droughts know
to depend to a greater extent on crops that require less water and that are drought resistant.
Likewise, the cyclical approaches used in traditional agriculture—including the use of animal
manure, composting, and crop rotation—are designed to make the most of resources that are
already on the farm, rather than importing them.

In contrast, the highly linear approach to industrialized agriculture enables farmers to ignore
local climate conditions and essentially import large amounts of water and fossil fuel energy
to produce a monoculture crop.

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Section 4.6 The Dependence on Water and Nonrenewable Energy

Impact of Water Consumption
Agriculture is the single largest user of
water globally, accounting for roughly 80%
of all water use in the United States and over
90% in most western states (USDA, 2019).
Large-scale irrigation systems allow mod-
ern farmers to grow crops in certain regions
where it would otherwise not be possible
to do so, such as rice production in desert
regions of Arizona. Roughly 40% of world
food production comes from land that is
artificially irrigated (Food and Agriculture
Organization of the United Nations, 2014),
and demand for irrigation water is pro-
jected to continue to increase in the future.

One area of concern associated with agriculture’s heavy dependence on water is the overex-
traction of groundwater. Overextraction occurs when water is pumped out of an underground
aquifer (an underground layer of water-bearing rock) at a rate that exceeds natural recharge
or replenishment of that supply. If you think of an underground aquifer as a bathtub or basin
filled with water, the rate of extraction would be water going down the drain, while the rate
of recharge would be water coming out of the tap and into the basin. Obviously, if more water
is going down the drain than coming from the tap, the water level in the basin will go down.
That is exactly what is happening in many key agricultural areas around the world today,
especially in parts of North Africa, southern Asia, China, and the United States. Many aquifers
in these regions contain “fossil water” that was deposited there over geological timescales.
Heavy extraction of water from these deposits is not offset by new water recharge, and as a
result water levels are dropping dramatically. As water levels drop, the land above it can sink
or subside. Overextraction of groundwater in coastal areas can also allow salt water from the
sea to intrude into freshwater aquifers, making them unsuitable for residential or agricultural
uses.

Another environmental problem associated with overuse of irrigation water in agriculture
is soil salinization. Most irrigation water contains small or trace amounts of salts from the
rocks in underground aquifers. When irrigation water is applied to farm fields, some of the
water evaporates, leaving a tiny residue of salt behind. Over time, as more and more water
gets added to a field and evaporates, more of the salt particles can build up in the soil. Soil
salinization can lower crop yields and damage or even kill some crop plants. It’s estimated
that over 20% of all irrigated cropland, mostly in dry areas, is impacted by soil salinization
and that the damage to crop productivity is over $25 billion each year (United Nations Uni-
versity, 2014).

Impact of Fossil Fuel Consumption
Energy use in agriculture is both direct and indirect. Direct energy consumption includes the
diesel fuel, propane, electricity, and other forms of energy used to power tractors, harvest-
ers, pumps, lights, driers, and other forms of farm equipment. Indirect energy consumption

Songbird839/iStock/Getty Images Plus
Agriculture accounts for as much as 90% of
all water use in some western states of the
United States.

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Section 4.7 The Issues With Animal and Meat Production

includes the energy used to transport crops, process foods, and produce the fertilizers and
other agricultural chemicals used in farming. It’s estimated that direct and indirect forms of
energy consumption in agriculture account for 19% of all energy use in the United States each
year (Pimentel, 2006).

Agriculture’s contribution to global climate change results from emissions of greenhouse
gases like carbon dioxide, methane, and nitrous oxide. Carbon dioxide emissions from agri-
culture happen directly as a result of burning diesel, propane, and other fossil fuels to power
farm machinery and equipment. Carbon dioxide is also released when forests are cut and
burned to make way for agricultural production. Agriculture is also a major producer of meth-
ane from livestock operations and rice farming, as well as nitrous oxide from fertilizer use.
Overall, it’s estimated that the global food system—including growing, processing, and trans-
porting crops—is responsible for up to one third of human-caused greenhouse gas emissions
(Gilbert, 2012).

4.7 The Issues With Animal and Meat Production

The global meat and dairy industry is massive and growing. Worldwide, the livestock sector
produces roughly 120 million metric tons of poultry, 120 million metric tons of pork, 72 mil-
lion metric tons of beef and veal, 15 million metric tons of meat from sheep and goats, and 827
million metric tons of milk and milk products each year (Food and Agriculture Organization
of the United Nations, 2018a). If divided equally among all of the people around the world,
this would result in an average global consumption of roughly 42 kilograms (92 pounds) of
meat per person and 107 kilograms (237 pounds) of milk and milk products per person per
year. In reality, levels of meat and milk consumption are highly uneven. For example, the aver-
age American or Australian eats over 90 kilograms (200 pounds) of meat per year, the aver-
age person in China or Vietnam eats about 50 kilograms (110 pounds) a year, and the average
Ethiopian, Indian, or Bangladeshi eats less than 4 kilograms (9 pounds) per year (Organisa-
tion for Economic Co-operation and Development & Food and Agriculture Organization of
the United Nations, 2018a). Producing meat and dairy products has a large environmental
footprint, and as developing countries become wealthier, it’s expected that their citizens will
incorporate more of these foods into their diets. This will likely aggravate some of the major
environmental issues associated with meat and dairy production, including managing animal
waste, preventing pollution, and dealing with antibiotic resistance.

Feeding Our Food
Before we discuss the direct environmental impact of the meat and dairy industries, it’s
important to understand the basic inefficiencies in our current system. To start, a signifi-
cant portion of the commercial crops grown on industrialized farms around the world is fed
directly to animals rather than to humans. In the United States, after excluding corn grown for
ethanol production, 50% of corn is fed to cattle, pigs, and chickens (USDA, 2015b). Over 70%
of the soybeans grown in the United States are for animal feed, mostly for chicken production
(USDA, 2015c).

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Section 4.7 The Issues With Animal and Meat Production

When looked at this way, we can link virtually all of the environmental problems associated
with agriculture to animal and meat production. Heavy use of chemical pesticides, overap-
plication of fertilizers, soil erosion and land degradation, water pollution and aquatic dead
zones, air pollution, and global climate change can all be linked to the agricultural production
of crops like corn and soy that are fed to animals.

In addition, feeding grains to animals that are then fed to humans is an inefficient way to feed
the world. Farm animals are fed well over 1 billion metric tons of grain a year, and roughly
80% of all farmland is utilized for raising animals or growing crops to feed animals (Food
and Agriculture Organization of the United Nations, 2019). And yet meat and dairy account
for just 18% of calories and 37% of protein consumed by humans each year. For example, it
takes as much as 24 kilograms (53 pounds) of grain in the form of animal feed to produce 1
kilogram (2.2 pounds) of beef. For pork, that figure is roughly 4 to 1, and for chicken about
3 to 1, as illustrated in Figure 4.3 (Wirsenius, Azar, & Berndes, 2010). This basic inefficiency
associated with meat production and consumption lies at the heart of debates over how to
feed a global population on track to hit 10 billion in the next few decades.

Waste Management Problems
Many of the environmental and health issues associated with large-scale, industrialized
approaches to meat production have to do with how these animals are raised. Today most
of the chicken, pork, and beef consumed in developed countries like the United States origi-
nates from what are known as concentrated animal feeding operations (CAFOs). The
USDA defines a CAFO as an animal feeding operation with at least 1,000 “animal units” con-
fined for at least 45 days a year. Because
an “animal unit” equates to 454 kilograms
(1,000 pounds) of live animal weight, the
USDA definition of a CAFO describes an
animal feeding operation that has at least
1,000 cattle, 2,500 pigs, 55,000 turkeys, or
125,000 chickens. In 2016 it was estimated
that there were just under 20,000 CAFOs in
the United States (USDA, n.d.).

One benefit of CAFOs is that they bring
many animals together in one concentrated
location instead of requiring a larger land
area for grazing. This has the potential to
cut down on overgrazing and soil erosion.
However, concentrating so many animals
together in a small space can create seri-
ous problems with waste management. For example, an average cow can produce about 30
kilograms (66 pounds) of manure per day, or 11 metric tons each year. A CAFO with 1,000
cows (most CAFOs are much larger than this) produces as much waste as a city of 10,000
people. Nationwide, annual production of animal waste from the meat industry is as much as
20 times greater than waste produced by humans (Hribar, 2010).

DarcyMaulsby/ iStock/Getty Images Plus
Modern meat production has many negative
environmental effects, from fertilizer use to
water pollution and waste management.

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119

Section 4.7 The Issues With Animal and Meat Production

Figure 4.3: Feeding our food

Feeding grains to animals to then be fed to humans is an inefficient way to feed the world.

Data from “How Much Land Is Needed for Global Food Production Under Scenarios of Dietary Changes and Livestock Productivity
Increases in 2030?” by S. Wirsenius, C. Azar, C., and G. Berndes, 2010, Agricultural Systems, 103 (https://www.sciencedirect.com/science
/article/pii/S0308521X1000096X).

3.5 kg

2.3 kg

Beef 1kg

Pork 1kg

Chicken 1kg

Eggs 1kg

Milk 1kg1.1 kg

2.7 kg

24.0 kg

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120

Section 4.7 The Issues With Animal and Meat Production

Environmental and health problems stem from both the sheer volume of waste and how
this waste is handled. Typically, animal waste from CAFOs is mixed with water to form a liq-
uid slurry and simply stored in open pits or lagoons to decompose over time. In traditional
approaches to agriculture, this waste could potentially serve as valuable fertilizer for crops.
However, in the case of CAFOs, there is often simply too much waste in one location to be uti-
lized on local farm fields. Also, because animals in CAFOs are often fed antibiotics and grain
treated with pesticides, their waste is often so contaminated that it is dangerous to apply it to
the soil. Nevertheless, it’s estimated that about half of the animal waste collected from CAFOs
is applied to nearby farm fields.

Some of this manure slurry runs off of fields and into nearby rivers, streams, and other water-
ways, where it can cause eutrophication and also contaminate drinking water supplies with
bacteria and pathogens. Some manure slurry stored in open pits and lagoons can seep through
the soil and into groundwater deposits. In other cases heavy rains and flooding can cause
these waste lagoons to overflow or even break open, dumping massive amounts of concen-
trated animal waste into nearby rivers and streams. When Hurricane Florence hit North Caro-
lina in September 2018, hundreds of hog farm manure lagoons either overflowed or failed
completely, severely contaminating nearby drinking water supplies (Pierre-Louis, 2018).

In addition to water pollution, CAFO waste management practices contribute to air pollution.
Manure lagoons and open pits found in CAFOs emit many different types of gases, including
some—like ammonia and hydrogen sulfide—that can be hazardous to human health in the
immediate area. Many of these gaseous emissions from CAFOs are also foul smelling, and they
can reduce quality of life and property values for nearby residents.

CAFOs are also a major source of greenhouse gas emissions (especially methane) that con-
tribute to global climate change. These methane emissions come both from the digestive sys-
tems of cows being raised for meat and from the breakdown of organic wastes in the manure
lagoons found in CAFOs. It’s estimated that raising livestock is responsible for about 36% of
methane emissions worldwide and for about 18% of all greenhouse gas emissions (U.S. Envi-
ronmental Protection Agency, 2019). As demand for meat and dairy increases worldwide,
these greenhouse gas emissions are also expected to increase and further worsen rates of
global climate change.

Antibiotic Resistance
Because CAFOs confine so many animals together in a relatively small space, they create ideal
conditions for the spread of infections and diseases among the animals. As a result, CAFOs
have historically made heavy use of antibiotics to try to prevent illness and to treat animals
that are already sick. It’s estimated that roughly 70% of “medically important” antibiotics
used in the United States each year are for animal production (Dall, 2016). However, recent
changes in federal guidelines governing antibiotic use in animals, combined with growing
public concern over the dangers of antibiotic resistance, appear to be resulting in declines in
antibiotic use in animal feeding operations (Dall, 2018).

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121

Section 4.7 The Issues With Animal and Meat Production

While in the short term this antibiotic use helps cut down on disease and increases productiv-
ity, it has a serious long-term consequence. Just as the overuse of pesticides and herbicides
has led to the development of resistant insects and weeds, overuse of antibiotics results in the
rise of antibiotic-resistant bacteria and disease organisms (see Figure 4.4). These antibiotic-
resistant bacteria can contaminate human food supplies as the animals are slaughtered and
can spread to drinking water supplies when manure lagoons overflow or seep into ground-
water. The Centers for Disease Control and Prevention (CDC, 2018) has now established clear
links between heavy antibiotic use in CAFOs and a rapid rise in antibiotic-resistant bacteria,
including salmonella and E. coli. As a result, the CDC and other public health experts have
been calling for a phase-out of routine antibiotic use in animal feeding operations, while the
meat industry has resisted and pointed to the benefits of antibiotic use on productivity.

Figure 4.4: Antibiotic resistance from farm to table

Antibiotic resistance has serious repercussions for human health.

“Antibiotic Resistance and Food Safety,” by Centers for Disease Control and Prevention, 2018 (https://www.cdc.gov/foodsafety/challenges
/antibiotic-resistance.html).

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Section 4.8 Moving Toward Sustainable Agriculture

4.8 Moving Toward Sustainable Agriculture

Our modern, industrialized agriculture system produces a staggering amount of food at rela-
tively low costs to consumers. On average, Americans spend less than 10% of their income
on food, half of what we spent a generation ago and far less than what people in other coun-
tries spend to feed themselves (USDA, 2018a). Despite this success, it’s quite likely that no
other human activity has as much of a destructive impact on the environment as agriculture.
Whereas traditional approaches to agriculture were based on maintaining and enhancing
natural capital, modern industrialized agriculture is designed around approaches that rely
on exploitation and depletion of those resources. There are concerns that our food’s costs to
society are not reflected in the prices we pay. Unless we fundamentally change the way we
grow, distribute, and consume food, we can only expect that the negative environmental and
health impacts of our food system will get worse as the population continues to increase.

The remainder of this chapter will examine how to meet the food and nutritional needs of
a growing population in ways that are sustainable. But what does it mean for agriculture
to be sustainable? Definitions of sustainable agriculture can be both simple and complex.
At a basic level, sustainable agriculture is farming that meets our needs in ways that do
not undermine critical natural capital systems and the ability of future generations to meet
their own needs. Once we get beyond this basic definition, however, we see that sustainable
agriculture involves issues of science, technology, the environment, economics, social equity,
government policy, and personal choices and preferences. Researchers have concluded that
no single approach or technological breakthrough will be enough to move us toward sustain-
able agriculture. Instead, we need an “all of the above” strategy that combines many different
approaches and practices (Springmann et al., 2018; Searchinger, Waite, Hanson, & Rangana-
than, 2018). The ideas in this chapter should not be considered in isolation or as “magic bul-
lets” for solving the environmental and health impacts of industrialized agriculture. Rather,
these practices and approaches should be viewed as being most effective when implemented
in a synergistic or combined fashion.

Many of the on-farm practices that are promoted as “sustainable” are ones that were common
in traditional agriculture and practiced for hundreds or thousands of years. These practices
are designed to build and maintain healthy soil, manage water effectively, minimize air and
water pollution, and promote a diversity of species and organisms on the farm and in sur-
rounding areas. That being said, simply returning to traditional agricultural practices used
before the Green Revolution might not be possible or practical at this stage. The key will be to
take some of the wisdom and knowledge built up over thousands of years of practicing tradi-
tional agriculture and combine that with the scientific and technical knowledge that enabled
the Green Revolution.

Crop Rotation and Intercropping
Crop rotation is the practice of planting different crops on the same piece of land every few
years. A related method is intercropping, or strip cropping, wherein a mix of different crops
are grown in the same area, as opposed to the monocropping of industrialized agriculture.

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Section 4.8 Moving Toward Sustainable Agriculture

Crop rotation and intercropping help maintain soil fertility because different crops have dif-
ferent nutrient needs for growth. Some crops can even enhance soil fertility and reduce the
need for fertilizers. For example, a farmer can grow corn—a nitrogen-intensive crop—in a
field one year and the following year grow legumes, which add nitrogen to the soil.

Crop rotation and intercropping also help reduce pest outbreaks, since pests tend to be crop
specific. By changing the crops grown in one field year to year or alternating the spacing of
crops in a single year through intercropping, pests are not given an opportunity to establish
themselves and spread over the area, which thereby reduces the need for pesticides.

Cover Crops
Common cover crops, such as alfalfa and clover, are planted on farm fields during the off-
season. Letting a field lay bare can lead to soil erosion through wind and rain. Using cover
crops can prevent erosion by helping hold the soil in place. Some cover crops can also enhance
soil fertility and reduce the need for fertilizers by returning nitrogen to the soil. Cover crops
prevent the influx of weeds and pests and reduce the need for pesticides.

Cover crops can simply be plowed into the soil at the start of the next growing season, where
they continue to enhance soil quality and nutrient levels as they break down and decompose.
Alternatively, these crops can be left on the field permanently and mowed like a lawn for ani-
mal feed. This latter approach is known as perennial agriculture because it involves leaving
these crops in place year after year.

Contour and Terrace Farming
Traditional agriculturists have adapted to
farming on hilly and steep land by practic-
ing contour farming and terracing. Contour
farming involves plowing sideways across
a hillside, following the natural contour of
the land. This creates small ridges or fur-
rows that trap soil as it slides down the hill,
preventing soil erosion and creating a series
of contoured strips along the side of the hill.

Terracing is used on even steeper terrain
and involves cutting into the hillside to cre-
ate a series of steps or platforms that can
hold soil and irrigation water in place to
grow crops. Terracing is a common feature
of rice cropping in mountainous regions of
Southeast Asia, where this approach has
been practiced for thousands of years.

naihei/iStock/Getty Images Plus
Farmers who live in steep areas rely on
techniques such as terracing, in which a series
of platforms are cut into the hillside to allow
crops to grow.

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Section 4.8 Moving Toward Sustainable Agriculture

Low-Till and No-Till Farming
Plowing, or tilling, fields for planting helps aerate the soil and cut down on weeds, but it
also leaves the surface bare, thereby increasing soil erosion, water evaporation, and water
demand. Low-till farming and no-till farming take a different approach, inserting seeds
directly into undisturbed soil. Instead of plowing up a field after each harvest, farmers leave
their fields covered in plants at all times. They use a device known as a no-till drill to make a
shallow cut in the soil, drop in seeds, and cover them. Low-till and no-till farming minimize
soil erosion, allow more organic material to accumulate on the surface, and help maintain
soil moisture much better than plowed soils. These approaches are commonly referred to as
conservation tillage.

Integrated Pest Management
Integrated pest management (IPM) is an approach to managing agricultural pests with
few or zero chemical pesticides. Note IPM’s goal of managing agricultural pests rather than
eliminating them. In IPM, tactics are tailored to the specific pest problem a farmer faces, as
opposed to simply dousing a field in chemical pesticides and killing everything in it. IPM strat-
egies might include the use of biological methods (introducing natural predators), altered
planting practices (crop rotation, intercropping), and even mechanical devices to vacuum
pests off of crops.

IPM has been used successfully in many different types of agricultural systems in every part
of the world. Apple farmers in Massachusetts, soybean farmers in Brazil, vegetable farmers in
Cuba, and banana farmers in Costa Rica have dramatically reduced pesticide use while main-
taining or even improving crop productivity through the use of IPM.

One of the most dramatic IPM triumphs was with rice agriculture in Indonesia. Throughout
the 1970s and 1980s, as more and more Indonesian farmers were adopting Green Revolution
rice varieties, the government heavily subsidized the purchase and use of chemical pesticides
to control outbreaks of brown planthoppers that threatened the rice crop.

However, over time, planthopper populations became resistant to many common forms of
pesticide. As farmers applied increasing amounts of the chemicals to try to control this pest,
they only succeeded in wiping out populations of beneficial insects (such as spiders) that
naturally preyed on the planthoppers.

By the late 1980s the Indonesian government took drastic action, banning most pesticides,
eliminating subsidies for others, and instituting a widespread IPM education program to
teach farmers how to control the brown planthopper using biological methods. By all mea-
sures this change in approach was a success. Pesticide use dropped by as much as 75%, while
rice yields actually increased slightly over time (Thorburn, 2015).

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125

Section 4.9 Considering Farm Policy, Economics, and Personal Choices

Integrating Crops and Livestock
A growing number of farmers are returning to the traditional integrated crop–livestock sys-
tems, in which a variety of crops and animals are raised on the same farm and animal wastes
are used as fertilizer. Recall that industrialized agriculture is a linear process that tends to
keep crop production and animal production separate, thereby removing a solution—using
animal wastes as fertilizer—and instead creating two problems: a need for synthetic fertilizer
and the disposal of massive amounts of waste.

Integrated crop–livestock systems are sometimes referred to as agroecology, permaculture, or
low-input farming. These systems are often complex and cyclical and require careful planning
and practice. However, when done well, integrated crop–livestock systems greatly enhance
soil fertility, reduce the need for synthetic fertilizers, raise animals in more humane and less
environmentally destructive ways, and help diversify local and regional farm economies.
Many of these integrated crop–livestock farming systems have benefited from strong local
consumer support, as discussed in the next section.

Each of these six traditional on-farm practices—crop rotation and intercropping, cover crops,
contour and terrace farming, low-till and no-till farming, IPM, and integrated crop–livestock
systems—has been demonstrated to reduce environmental impacts, increase crop yields, and
save farmers money. However, all six also take careful planning, knowledge, and patience to
implement. It’s also the case that many of the decisions that farmers make about what to grow
and how to grow it are influenced by government policy, economic factors, and the prefer-
ences and personal choices that consumers make every time they purchase food. These issues
are the subject of Section 4.9.

4.9 Considering Farm Policy, Economics,
and Personal Choices

Like any other business or enterprise, farmers make decisions about what to grow, how to
grow it, and where to market it based in large part on the policy environment and market
conditions in which they operate. In the United States and other developed countries, gov-
ernment policy has a significant impact on decisions that farmers make about what and how
to farm. Likewise, farmers would be foolish not to consider or be influenced by consumer
preferences, choices, and tastes. Therefore, in attempting to move toward more sustainable
approaches to agriculture, it’s important to examine how we might influence policy, economic
factors, and consumer choices in ways that encourage farmers and other actors in the food
system to operate more sustainably.

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Section 4.9 Considering Farm Policy, Economics, and Personal Choices

Farm Policy
By its very nature, farming is a somewhat risky enterprise. Weather-related disasters like
droughts, floods, tornadoes, and hurricanes can wipe out an entire season’s worth of labor
and investment. For these reasons, governments in developed countries tend to be heavily
involved in the farm economy. Some of this government spending goes to support agricul-
tural research and development at universities and scientific institutes, food inspection and
safety, infrastructure like rail and irrigation systems, and education and outreach programs
for farmers. However, the bulk of this government spending—close to $500 billion a year
from the top 21 food-producing countries worldwide—goes to direct and indirect subsidies
to farmers and farm enterprises (Worldwatch Institute, 2014). Direct subsidies are payments
made directly to farmers by the government, whereas indirect subsidies include things like
crop insurance and price supports that are designed to help keep farming operations finan-
cially viable.

Proponents of these subsidy payments argue that they are necessary to help farmers man-
age the risk inherent in this line of work and that they benefit small family farms and local
economies. Detractors point to a number of serious problems with this subsidized approach.

Issues With Subsidies
First, subsidies allow farmers to sell their crops overseas below the cost of production. When
cheap exports of corn, wheat, or rice are sold in poorer, developing countries, they undercut
local farmers and drive them out of business, since governments in these countries cannot
afford to subsidize their own farmers. This creates a cycle of dependence in which local food
production drops, more cheap food is imported, and local food production drops further.

Second, farm subsidies can be linked to some of the environmental problems described ear-
lier. Subsidies tend to encourage farmers to overproduce, which brings more land than is
needed into production, including lands prone to erosion (Edwards, 2018). As production
increases, so does the use of fertilizers and pesticides, as well as the environmental problems
associated with their application. In addition, since subsidies are usually targeted at a narrow
range of “commodity crops” (like corn and soybeans), they tend to discourage crop rotation
and intercropping since farmers are encouraged to maximize acreage planted with the sub-
sidized crops (Edwards, 2018).

Lastly, there is little evidence that subsidies are important in protecting family farms and sup-
porting local farm economies. Instead, the bulk of farm subsidies go to support some of the
largest and most financially secure farm operations. The U.S. government spends over $20
billion a year on farm subsidies, and it’s estimated that over 70% of that amount goes to just
10% of America’s farm operations (Edwards, 2018; EWG, 2019b). In 2017 there were a total
of 389 farm operations in the United States that each received at least $1 million in govern-
ment subsidies, including 11 operations that received between $5 million and $9.9 million
each (Andrzejewski, 2018). Likewise, millions of dollars in farm subsidy checks are mailed
to addresses in Chicago, Houston, New York, and even Beverly Hills every year—not exactly
locations that fit the definition of a local farm economy (Andrzejewski, 2018).

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Section 4.9 Considering Farm Policy, Economics, and Personal Choices

Alternative Approaches
Instead of a farm subsidy program that undercuts farmers in poor countries, actually encour-
ages farmers to practice unsustainable agriculture, and enriches farmers and farm operations
that are already financially secure, these billions of tax dollars could be used in other ways.

Sustainable agriculture advocates argue that simply eliminating these subsidy programs
could go a long way toward getting farmers to rethink what they grow and how they grow it.
Alternatively, some of the billions of dollars spent annually on farm subsidy payments could
be directed to programs that reward farmers for practicing conservation farming and sustain-
able agriculture.

Ultimately, such a change involves political decisions, since the beneficiaries of current sub-
sidy programs have a lot of political influence. But there is strong evidence that such a change
in policy can reduce government spending, bring environmental benefits, and actually sup-
port those farmers and farm communities most in need of help. Therefore, it’s possible to
imagine a political alliance across the ideological left–right spectrum that could advocate for
such a change.

Consumer Choices and Preferences
Perhaps more than any other factor, individual consumer preferences and decisions can have
the biggest impact on how fast we move toward sustainable agriculture. What we choose to
buy and eat, and where we choose to buy it, sends direct signals to farmers and other busi-
nesses in the food system.

Choosing Locally Sourced Foods
Currently, the U.S. commercial food system is dominated by large-scale, industrialized farm-
ing and food distribution enterprises. Food produced by these businesses often travels long

Learn More: Farm Subsidies in Your State

Research by the EWG and a group called Open the Books sheds light on how farm subsidy
programs in the United States are mostly enriching financially secure farm operations
and wealthy farmers while doing little to assist the vast majority of smaller, family farm
operations. You can see how farm subsidies have been allocated in your state from 1995
to 2017 by visiting the EWG Farm Subsidy Database (https://farm.ewg.org) and clicking
on your state. You can also see how many of the 389 farm operations that received over
$1 million in 2017 are in your state by exploring the appendix of the Open the Books report
Harvesting U.S. Farm Subsidies (https://issuu.com/openthebooks/docs/usfarmsubsidies_08
072018?e=31597235/63670406).

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Section 4.9 Considering Farm Policy, Economics, and Personal Choices

distances before reaching its ultimate consumer. It’s estimated that a typical food item sold
in a conventional American grocery store travels 2,400 to 4,000 kilometers (1,500 to 2,500
miles) before being purchased (Worldwatch Institute, n.d.). The environmental impact of all of
those “food miles”—combined with the environmental impacts of industrialized agriculture
discussed earlier in this chapter—is driving many consumers to reconsider their food pur-
chases in terms of both what they buy and where they buy it. This trend has been described
as the “local foods movement” and the “farm-to-table movement,” and people who buy and
consume more locally produced foods are described as “locavores.” What these efforts have in
common is an emphasis on purchasing locally produced foods that are in season.

Consumers can connect with local farmers in a few different ways. Farmers’ markets—where
local farmers gather to sell their products directly to consumers—have become much more
common in many areas of the United States in recent years. In the mid-1990s there were
fewer than 1,800 farmers’ markets across the country. That number rose to almost 4,700 by
2008 and to well over 8,000 today (Farmers Market Coalition, 2019). Farmers’ markets help
support small-scale local farms, involve much less transportation and packaging, and offer
consumers fresh fruits, vegetables, and meats in place of many of the highly processed foods
found in supermarkets.

Consumers can also connect with local farmers through a community-supported agricul-
ture (CSA) program. In a typical CSA program, a consumer pays up front for a “share” of a
local farmer’s crops or farm products (including meat and eggs). In return, the consumer
receives a regular delivery of fruits, vegetables, and other products from that farm over the
course of the growing season. CSA programs often offer consumers the opportunity to visit
and even volunteer to work on the farm they are supporting. This helps bring people in closer
contact with where their food comes from, how it’s grown, and what’s involved in bringing
food from the farm to the table. While estimates of the number of CSA programs are harder
to come by, a 2015 USDA report estimated that there were over 167,000 U.S. farms that pro-
duced and sold food for local markets through farmers’ markets, CSA programs, and other
local food initiatives (USDA, 2015a).

One other example of the move toward local
foods is the rise of urban farming. Urban
farming repurposes unused space—such
as rooftops, vacant lots, and even roadside
medians—in heavily populated city areas.
In the United States, urban farming pro-
grams often grow out of need, since many
inner-city areas are food deserts—areas
where it is difficult to purchase affordable,
good-quality fresh food. Urban gardens and
urban farming programs are now wide-
spread in most major cities of the United
States, including New York, Chicago, Detroit,
Cleveland, Memphis, Baltimore, and Atlanta.

To find out more about local food options in your area, check out Close to Home: Developing a
Local Diet.

BrasilNut1/iStock/Getty Images Plus
A shift toward local foods includes urban
farming, which repurposes unused space in
heavily populated areas.

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129

Section 4.9 Considering Farm Policy, Economics, and Personal Choices

Close to Home: Developing a Local Diet

There are a number of environmental benefits associated with eating local foods. Fruits,
vegetables, and other perishables do not need to be transported very far or preserved for
very long when they are produced close to consumers. As a result, local food options often
result in less energy use and fewer greenhouse gas emissions. Crops that are well adapted
to local climates also require fewer chemical inputs and less water management during
production.

Local foods provide a number of social benefits as well. They build community by fostering
relationships between growers and consumers. Some also argue that local food systems
increase food security by diversifying food production. In our global food system, crops are
often produced on a small number of very large farms. This means that diseases, natural
disasters, and market disruptions that impact one region can have consequences for food

availability all over the world. Local food
systems, on the other hand, must rely on a
large number of smaller food producers, so
consumers have other options if a few farms
have a bad year.

Purchasing local food can also help local
economies generate wealth. Rather than
sending money to a grower on the other side
of the world, local foods support local farmers.
These individuals can then use that wealth to
support other community organizations and
local businesses.

Local foods address several dimensions of
sustainability, and arguments like these have
convinced a lot of people to reconsider their

eating habits and join the local food movement. Most just try to incorporate a few local
options into their diet, but some try to survive mostly or entirely on locally produced foods—
all the more impressive when you consider that very few fruits and vegetables are available
year-round in most locations.

To explore what it would mean to eat a local diet in your location, take a look at the Seasonal
Food Guide website that summarizes local produce availability. After selecting your location,
scroll through the different harvesting seasons and note the foods that might be seasonally
available. Do you think you could create a diet that incorporates more local produce? Are
there certain times of the year when eating local becomes much more difficult? What are
some strategies that you could use to continue eating the local foods you love even when they
are not in season?

To get your hands on some local ingredients, explore Local Harvest, an online directory
of local food growers and vendors. Many regions have one or more farmers’ markets that
gather several growers in one convenient location. Individual farms in your region might also
offer subscriptions to CSAs that provide you with an assortment of goods over the course
of a growing season. Of course, the most local option of them all is to grow your own food
around your home. If this sounds exciting to you, the USDA has a variety of home gardening
resources that might help.

kasto80/iStock/Getty Images Plus
Buying food from local farmers
helps local economies and fosters
relationships within the community.

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130

Section 4.9 Considering Farm Policy, Economics, and Personal Choices

Choosing Organic
Yet another way individual consumers can push for sustainability in our food system is
through organic foods. Organic food is produced through methods that comply with the fed-
eral standards of organic farming. Because organic farming requires that farmers forgo the
use of synthetic pesticides and fertilizers, among other requirements, it is generally better for
the environment than conventional approaches to agriculture. More and more Americans are
choosing to purchase foods that are certified organic, with organic food sales now valued at
over $35 billion annually in the United States alone (USDA, 2017).

However, organic farming is not always the most sustainable option. For example, should you
buy organic apples shipped more than 4,000 kilometers (2,500 miles) across the country or
locally grown but nonorganic apples? The more sustainable choice might be to go with the
latter.

Choosing Less Meat
A final dietary decision consumers can make is how much meat to consume, which can have
a significant effect on the sustainability of our food system. A typical Western diet is high in
sugar, fats, refined carbohydrates, meat, and dairy. Not only is this diet a problem in terms of
personal health, it also tends to have a greater environmental impact than other diet types.

The World Resources Institute (WRI) estimates that beef production accounts for almost half
of U.S. agricultural land use and greenhouse gas emissions from farming while only providing
for 3% of the calories consumed by Americans (Ranganathan et al., 2016). This is because of
the basic inefficiency associated with converting grains to animal protein. A shift from beef
to less intensive forms of meat like chicken or reducing meat consumption overall can bring
significant environmental gains and help consumers reduce their environmental footprint.
Much less agricultural land is required to support a more vegetarian diet, which translates
into less energy and water use as well. Even small moves toward lowering meat consump-
tion can have a big impact. One study estimated that if every American picked 1 day a week
to avoid meat (such as a “meatless Monday”), it would reduce greenhouse gas emissions at
a level equivalent to taking 30 million to 40 million cars off the road for 1 year (Center for
Biological Diversity, 2019).

Food Loss and Waste
Food loss refers to food that is discarded
before it even reaches the consumer; that is,
during the production, processing, and dis-
tribution phases. Food waste refers to food
that is discarded directly by consumers,
restaurants, or other institutions like hospi-
tals and schools. It’s estimated that world-
wide approximately 1.6 billion metric tons
of food—one third of all food produced—
is lost or wasted every year. This wasted
food is estimated to be worth $1.2 trillion

peder77/iStock/Getty Images Plus
Every year, one third of all food produced
worldwide is wasted.

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131

Section 4.10 The Role of Science and Technology

annually; at the same time, close to 1 billion people around the world face food scarcity and
shortages. In the United States the annual rate of food loss and waste is actually higher (40%)
than the global rate, and it’s estimated that an average American family of four throws away
526 kilograms (1,160 pounds) of food every year (Lipinski et al., 2013).

Food loss and waste is challenging to address because the global food distribution system
is complex, and waste occurs at every stage of that system. A 2013 WRI report found that
food loss and waste differed significantly from country to country. In the poorer countries of
Africa, Latin America, and Asia, between one half and three fourths of all food waste occurs
at the production stage and the handling and storage stage of the food distribution system.
This is due in large part to a lack of adequate infrastructure in the form of roads, refriger-
ated warehouses, and other modern food storage facilities. In contrast, in North America and
Europe, well over half of all food loss and waste occurs at the consumption stage and can be
tied directly to the behaviors of individual consumers and businesses like restaurants and
caterers (Lipinski et al., 2013).

The WRI report recommends various programs and initiatives to help cut down on food loss
and waste. These include

• food redistribution programs that send food that would otherwise be wasted to food
banks and shelters;

• increased access for poor farmers to food storage facilities;
• standardized and clear food date labeling (such as “use by,” “sell by,” and “best

before” labels) to reduce unnecessary disposal of food that hasn’t spoiled;
• consumer awareness campaigns to teach strategies for reducing food waste; and
• reduced portion sizes in restaurants.

Two examples of these kinds of efforts come from the United Kingdom and New York City.
From 2007 to 2010, the United Kingdom implemented the Waste and Resources Action Pro-
gramme, which achieved a 13% reduction in household food waste and an additional 9%
reduction in food waste at the retail stage. These savings came through simple and com-
monsense strategies that not only cut waste but also helped consumers and businesses save
money. These efforts included education campaigns targeted at consumers on reducing food
waste, as well as programs for businesses to channel food that might otherwise be discarded
to charities or composting facilities (Waste and Resources Action Programme, n.d.). In New
York City a program known as Rescuing Leftover Cuisine organizes hundreds of volunteers
every day to collect food that would otherwise be thrown away by restaurants, grocery stores,
and other businesses and distributes that food to shelters, soup kitchens, and social service
agencies. The program estimates that since 2013 it has rescued close to 1.3 million kilograms
(2.8 million pounds) of food and provided over 2.3 million meals to people in need (Rescuing
Leftover Cuisine, 2019).

4.10 The Role of Science and Technology

This section will examine how science and technology are enabling agriculture to be more
productive, efficient, and environmentally friendly—another option in our “all of the above”
approach to meeting the food and nutritional needs of 10 billion people. The section will

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132

Section 4.10 The Role of Science and Technology

review a variety of approaches—including use of the Global Positioning System (GPS), drones,
and robots in farming—that fall under the definition of “precision farming” or “site-specific
crop management.” The section will also consider two approaches to growing food that do
not require the use of soil: aquaponics and hydroponics. The section will conclude with a case
study of how the tiny country of the Netherlands has become a world leader in sustainable
agriculture and agricultural productivity, in part through the widespread adoption of a vari-
ety of precision farming approaches.

Precision Farming
Throughout the world, more and more farmers are adopting high-tech approaches to manag-
ing their crops. This includes using GPS, satellite imagery, soil moisture sensors, drones, and
even robots to provide them with real-time data on crop and field conditions. Farmers use
this data to make more precise decisions, like when and where to irrigate, whether pesticides
or fertilizers are needed for certain crops, and when the ideal time is to harvest a crop. Thus,
this type of high-tech farming is known as precision agriculture.

For example, almond farmers in water-scarce regions of California rely on networks of small
moisture sensors buried in the soil throughout their orchards to determine when and where
water is needed. The sensors feed data to an automated water pumping system that delivers
just the right amount of water to just the right location.

Likewise, corn farmers can now make use of a device known as a Rowbot that applies precise
amounts of fertilizers to the crop based on data provided by soil and crop sensors. Aerial
drones can be mounted with sensors that can detect whether some plants are diseased or
need nutrients, and that data can be used to target spraying or fertilizer application to spe-
cific locations. These technologies improve on the conventional practice of simply irrigat-
ing or spraying pesticides and fertilizers across an entire field without any consideration for
site-specific differences in conditions across the farm. The goal of this high-tech, precision
agriculture is to increase productivity, decrease the use of inputs like water and agricultural
chemicals, and minimize the impact of agriculture on the environment. All of these outcomes
have the added benefit of improving a farmer’s profitability.

Farming Without Soil
Hydroponics and aquaponics are ways to grow crops without the use of soil. Hydroponics
grows plants by suspending them with their roots placed in a water–mineral nutrient solu-
tion. Aquaponics builds on this idea by incorporating aquaculture, or raising aquatic animals
like fish, with a hydroponic system (see Figure 4.5). One advantage of aquaponics is that the
waste products from the fish portion of the system can be used as fertilizer for the plants, and
some of the plant material can be fed to the fish. In this way, aquaponics resembles the kind of
closed-loop, cyclical system involving crop–livestock integration common in traditional farm-
ing, just with a modern approach.

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133

Section 4.10 The Role of Science and Technology

Figure 4.5: Aquaponics

This aquaponics example is a self-contained, closed-loop system that requires only sunlight and
rainwater.

Adapted from normaals/iStock/Getty Images Plus

Rainwater

Rainwater tank

Rainwater

Hydroponic crops

Irrigation system

Fish tank generates
nutrients from waste

Fish

Hydroponics and especially aquaponics offer a number of benefits over conventional
approaches to farming. Because water is recycled through these systems, hydroponics and
aquaponics use only about one tenth the amount of water used by conventional farming.
Since these are usually indoor systems, they also do not require as much chemical pesticide
application. Hydroponic and aquaponic systems can be built at many different scales and can
be an important part of urban farming and education programs.

On the other hand, there are a few challenges and limitations to the use of hydroponics and
aquaponics. These systems require a fair amount of up-front investment and specific knowl-
edge to build and maintain. Likewise, indoor hydroponic and aquaponic systems require
energy and electricity for lighting and climate control.

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134

Section 4.11 Genetic Engineering and Genetically Modified Organisms

Case Study: High-Tech Farming in the Netherlands
The small European country of the Netherlands is a pioneer in the use of precision agricul-
ture techniques as well as hydroponics. For almost 2 decades, the Dutch have been focusing
government and private resources on sustainable agriculture, with impressive results. Water
use for key crops has dropped almost 90%, chemical pesticide use in greenhouses has been
almost eliminated, and poultry and livestock producers have reduced the use of antibiotics
by 60% (Viviano, 2017). At the same time, crop yields and productivity have risen across
the board, and the Netherlands is a world leader and top exporter of potatoes, onions, and a
number of other vegetables.

Part of this success comes from the widespread use of climate-controlled greenhouse com-
plexes. The Dutch countryside is dotted with clusters of agricultural greenhouses, in which
farmers can carefully control conditions to maximize productivity and minimize inputs. The
Dutch have also fully embraced the use of drones, soil and moisture sensors, robots, and GPS
in agriculture. In many cases energy to heat the greenhouse complexes comes from ground-
source geothermal systems, a sustainable and nonpolluting energy source. Overall, the Dutch
are proving that large strides, not just incremental change, can still take place in agriculture.

4.11 Genetic Engineering and Genetically Modified
Organisms

For almost as long as humans have been farming, they have been manipulating plant and ani-
mal species to favor some traits over others. Crossbreeding and selective breeding have been
used by farmers for thousands of years to favor crops that produce more seeds or fruit or to
favor animals that produce more wool or milk.

However, all of those efforts involved favoring or breeding for traits that already existed
within a species or between closely related species. For example, a rice plant that produced
abundant grain but was easily damaged by wind could be crossbred with a different rice plant
that produced less grain but had a stronger stem that could withstand wind. The resulting
rice plant, after repeated breeding, would feature both desirable traits—high grain produc-
tion and strong stems—in a single seed.

Genetic engineering, or the genetic modification of crops and animals, represents a funda-
mentally new approach. Genetic engineering involves the removal of genetic material (genes)
from one organism and combining it with the DNA of another. These gene transfers are often
described as “novel” because they would never occur on their own in the natural world. For
example, genetic material from fish high in omega-3 fatty acids has been inserted into soy-
bean plants to try to produce soybean oil high in the fatty acids believed to be beneficial to
heart health. Genetically modified organisms (GMOs) are organisms that have had their
genetic material modified in ways that would not have been possible in nature.

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135

Section 4.11 Genetic Engineering and Genetically Modified Organisms

Advantages and Opportunities
Proponents point to a number of advantages and opportunities in genetic engineering and
GMOs. They argue that genetic engineering opens up new ways to introduce desirable traits
into plants and animals. These include both “input” traits—such as developing animals that
are resistant to disease or developing crops that are resistant to drought—as well as “output”
traits—like breeding crops that have higher nutritional content. A few examples of GMOs that
have already been developed help illustrate these arguments.

Almost 20 years ago, crop scientists in Asia engineered a new rice variety that contains beta-
carotene (vitamin A) in the grains. Vitamin A deficiency is a serious public health challenge
in poorer regions of Asia, where rice is a staple crop. The new rice variety, named “golden
rice” because of its yellow color, has not yet been widely adopted by farmers or accepted by
consumers in the region.

As another example, genetic material from a bacteria known as Bacillus thuringiensis (Bt) has
been successfully inserted into corn and cotton plants to fight insects. Bt produces a toxin
that kills insects that eat the plant but is not harmful to people. When insects feed on what is
known as Bt corn or Bt cotton, they are poisoned and die, reducing the need for applications
of pesticides on these crops. Bt corn and cotton currently account for about 80% of the total
production of these crops in the United States each year (USDA, 2018b).

Finally, Canadian scientists have recently taken genetic material from Pacific chinook salmon
as well as from another fish known as ocean pout and inserted these into Atlantic salmon to
promote faster growth. These “GM salmon” grow twice as fast as and consume less feed than
conventional Atlantic salmon, potentially lowering the cost of production of this healthy food
option. In 2015 the U.S. Food and Drug Administration approved the sale of GM salmon in
this country, although actual marketing of this fish in the United States was not scheduled to
happen until 2019.

A Cautionary Word
Despite the apparent advantages of genetic engineer-
ing and GMOs, some scientists, public health experts,
consumer advocates, and environmental groups have
come out strongly against this approach. Most of the
arguments against genetic engineering are based on
issues of safety and ethics and on whether this tech-
nology is resulting in even more market power and
control for large corporations.

In terms of safety, concern has been expressed for
both human health impacts and unintended environ-
mental consequences of GMOs. Because GMOs involve
the creation of “novel” or new organisms, there are
concerns that they could result in an increase in aller-
gic reactions in some people, although it’s not clear
yet whether this is already happening. Likewise,
GMOs might be having unintended environmental

Ginton/iStock/Getty Images Plus
It’s not yet clear how genetically
modified foods could affect our
environment in the long run. These
types of crops could be affecting
other species, such as the butterflies
visiting the fields for pollen.

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136

Section 4.11 Genetic Engineering and Genetically Modified Organisms

consequences. For example, some butterfly species appear to have been negatively impacted
by consuming pollen from Bt corn.

At a more basic level, many people argue against genetic engineering and GMOs on ethical or
philosophical grounds. They suggest that genetic engineering is “tinkering with nature” and that
GM foods are not natural and are instead a type of “Frankenfood.” This contributes to arguments
for mandatory labeling of foods that contain GMOs, something that is not required in the United
States but is more common in other countries. (See also Apply Your Knowledge: Are GMOs Safe?)

Lastly, because research, development, and marketing of many GMOs are dominated by large
multinational corporations, many skeptics of genetic engineering argue that this technology is
concentrating more power over our food system in the hands of a small number of companies.
These corporations are patenting the new organisms they develop, giving them market control
over basic food commodities. Overall, critics and skeptics of genetic engineering argue that
perhaps we should adopt more of a “precautionary principle” when it comes to this technology
and allow for its development and commercialization after more careful review and testing.

Apply Your Knowledge: Are GMOs Safe?

Scorpion DNA in cabbage? Corn that is immune to herbicides? GMOs are certainly very
strange, and some people are worried that they represent a health risk to the humans who
consume them. This feature box will analyze some data at the heart of this conversation and
explore both sides of the GMO debate.

The data in Figure 4.6 come from a 2003 experiment designed to understand the health risks
of consuming genetically modified tomatoes (Chen et al., 2003). In this study researchers began
with young rats that were divided into four experimental groups. Three groups were fed diets
containing different amounts of disease-resistant tomatoes that were modified with virus
DNA. The remaining group of rats was fed a non-GMO diet in order to provide an example of
normal rat development. This provided a baseline measurement that the other groups could
be compared against, which researchers call an experimental control. Rats were weighed each
week of the 4-week study, and their growth trends are shown in Figure 4.6. Based on this data,
do you think that genetically modified tomatoes impacted the growth of the rats in this study?

At first glance, you might notice that the data points fall really close to one another. In fact,
it is even hard to tell one point from another because the individual symbols overlap. We
can take this analysis a step farther if we notice the error bars that are associated with
each data point. Because experiments are never perfect, measurements like these are just
our best attempts to approximate the “true” values that describe the system. Therefore, we
often calculate error bars to represent the uncertainty of our measurements. In general, the
ranges indicated by the error bars are where we are most likely to find the “true” value of our
measurement. If we take this into account, we might notice that all of the data points at each
time interval have overlapping error bars. This means that all of the data points might share
the same “true” value. In this situation, we cannot make an argument that our data points
are statistically different from one another. It appears that the rats consuming the genetically
modified diets behave like the control rats.

The rats in this experiment were similar in other ways too. In addition to growth, the
researchers in this experiment compared the blood, organs, and biological processes of all
the rat groups, and none of these measurements showed statistical differences.

(continued)

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137

Section 4.11 Genetic Engineering and Genetically Modified Organisms

Figure 4.6: Male and female rat growth with GMO diets

Plots showing male (a) and female (b) rat growth over the course of the 4-week study.

Data from “Safety Assessment for Genetically Modified Sweet Pepper and Tomato,” by Z. Chen, H. Gu, Y. Li, Y. Su, P. Wu, Z. Jiang,
. . . L. Qu, 2003, Toxicology, 188.

300

250

200

150

100

50

0

10 432

W
e
ig

h
t

(g
)

Time (weeks)

(a)

300

250

200

150

100

50

0

10 432

W
e
ig

h
t

(g
)

Time (weeks)

(b)

Control
Little GMO
tomato content

Moderate GMO
tomato content

High GMO
tomato content

Control
Little GMO
tomato content

Moderate GMO
tomato content

High GMO
tomato content

Apply Your Knowledge: Are GMOs Safe? (continued)

(continued)

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138

Section 4.11 Genetic Engineering and Genetically Modified Organisms

The Bottom Line
Regardless of what position one takes on genetic engineering, the reality is that GMOs are
already in widespread use and are present in many of the processed foods sold in American
supermarkets. Though only introduced in roughly the past 20 years, it’s estimated that in the
United States today, 94% of all soybeans, 96% of all cotton, and 93% of all corn being grown
are in the form of genetically engineered varieties (USDA, 2018b). Likewise, it’s estimated
that well over 70% of all processed foods sold in the United States contain at least some GMO
ingredients (Center for Food Safety, 2019).

Globally, the land area planted with GM crops has grown from just over 1 million hectares
(2.5 million acres) in the late 1990s to almost 200 million hectares (494 million acres) today
(Silva, 2017). The United States leads in terms of land area planted with GMOs, followed by
Brazil, Argentina, India, and Canada. However, widespread adoption of GM crops is uneven. In
Europe some countries have placed outright bans on the cultivation of GM crops, and strong
anti-GMO sentiment among consumers keeps the demand for foods made with GMOs well
below what it is in the United States.

Apply Your Knowledge: Are GMOs Safe? (continued)

Several other studies have reached similar conclusions about other GMO foods. Researchers
have found no negative consequences for rats that consumed GMO sweet peppers, rice,
potatoes, and corn, among other GMO crop varieties (Chen et al., 2003; Hammond et al., 2006;
Schrøder et al., 2007; Seek Rhee et al., 2005). Other studies have explored long-term exposure
to GMO foods over several generations of reproducing rats, and once again, GMOs do not seem
to pose a significant risk (Seek Rhee et al., 2005; Brake, Thaler, & Evenson, 2004).

Does that mean GMOs are safe? Even though studies like these provide us with important
information, it is also important to think critically and recognize the limits of this
information. The studies mentioned were carried out on a few types of food with populations
of rats for limited amounts of time. Unfortunately, we still do not know for sure how people
will react to a variety of genetically modified foods over the course of human lifetimes and
generations. Even though much of the science suggests that GMOs are safe to eat, we may not
know for sure until people have been eating them consistently for several decades.

GMOs demonstrate that matters of health and the environment often get messy when a lot
is at stake. To make the best decisions going forward, we need to make sure that we pay
attention to the best information available. This often requires us to seek out and understand
the most reliable science behind a particular issue. At the same time, we need to question
that information and recognize the gaps in what is known about a particular topic. As is often
the case, the loudest voices in the GMO debate are coming from the two extremes, and the
best path forward may lie somewhere in the middle.

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139

Bringing It All Together

Ultimately, debates over the advantages, disadvantages, and future of genetic engineering and
GMOs boil down to questions of whose opinion counts and how we should approach risk. Like
many other public health and environmental controversies, it’s easy to find experts on both
sides of the GMO debate. It’s also the case that some of the promises and potential for GMOs
have been exaggerated, furthering suspicion that this technology is really designed to enrich
powerful corporations. However, given the need for an “all of the above” approach to agri-
culture in order to feed a growing population without wrecking the environment, it seems
shortsighted to completely rule out the use of genetic engineering unless stronger evidence
emerges of negative public health or environmental impacts.

Bringing It All Together

Dutch plant scientist Ernst van den Ende summed up the agricultural challenge facing the
world today by pointing out that we must produce more food in the next 40 years than all of
the food ever produced by all farmers over the past 8,000 years (Viviano, 2017). Given the
environmental impacts that agriculture is already imposing on the planet, we need to figure
out ways to produce food in a more sustainable fashion. Agricultural activities already push
us close to planetary boundaries for water use, biodiversity loss, nitrogen pollution, and
global climate change, so doing more of the same is simply not an option.

In short, a new Green Revolution—one that focuses not just on crop productivity but also on
environmental considerations, diet choices, food waste, agricultural policy, and new tech-
nologies—is in order. Ideas for how to bring about this revolution, both old and new, were
also covered in this chapter, and many of these involve the actions and efforts of individual
consumers.

The next chapter will take a more in-depth look at one of the most critical resources needed
for and impacted by agriculture: water. We’ll see that continued wasteful use of water by
agriculture simply cannot continue, given other pressures being placed on world water
supplies.

Additional Resources

Food Security and Sustainability

In this TED Talk, Sara Menker describes a rapidly approaching global food crisis and the
steps we can take today to avoid it.

• https://www.youtube.com/watch?v=OzA6jRYjVQs

The WRI has an excellent collection of reports and data on food, agriculture, and their con-
nection to the environment. In particular, the 2018 WRI report Creating a Sustainable Food
Future provides a “menu” of options for how to feed a world of 10 billion people without
destroying the environment in the process.

• https://www.wri.org/our-work/topics/food

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140

Bringing It All Together

Climate change may threaten the varieties of crops we grow today. In this TED Talk, Cary
Fowler describes how a global seed bank is being used to protect our food future.

• https://www.youtube.com/watch?v=Uwl012o8P7I

The National Academies of Sciences, Engineering, and Medicine recently published a com-
prehensive report on how science and technology will change agriculture in the years ahead.
Some are calling the report a “road map for a second green revolution.”

• https://www.nap.edu/catalog/25059/science-breakthroughs-to-advance-food
-and-agricultural-research-by-2030

The Johns Hopkins University Center for a Livable Future has an excellent Food Systems
Primer that contains a lot of resources for anyone interested in learning more about our
food system and its impact on the environment.

• http://www.foodsystemprimer.org

Food Safety

Scientific American published a troubling story on how drug-resistant bacteria get into our
food system and threaten our health.

• https://www.scientificamerican.com/article/how-drug-resistant-bacteria
-travel-from-the-farm-to-your-table

Sustainable Farming

The Yale Environment 360 online newsletter/magazine has an excellent collection of essays
and features on issues of food and agriculture.

• https://e360.yale.edu/topics/food-agriculture

The Solutions Journal recently published an interesting essay on “Solutions for a Win–Win
Partnership Between Agriculture and Biodiversity.”

• https://www.thesolutionsjournal.com/article/solutions-win-win-partnership
-agriculture-biodiversity

Consumer Choices and Preferences

In addition to the Local Harvest website introduced in the Close to Home: Developing a Local
Diet feature box, the USDA Agricultural Marketing Service offers two different databases
that can help you connect with local food. The first provides information on local farmers’
markets and the second on community-supported agriculture programs that might exist in
your area.

• https://www.ams.usda.gov/local-food-directories/farmersmarkets
• https://www.ams.usda.gov/local-food-directories/csas

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141

Bringing It All Together

Choosing less meat is one way to shrink your environmental footprint, but it can be a hard
change to make. In this TED Talk, food innovator Bruce Friedrich talks about how science is
generating appealing alternatives to meat.

• https://www.youtube.com/watch?v=vZCGSP3A0Fo

Plant Chicago is an interesting project focused on urban agriculture, energy conservation,
and waste minimization.

• https://plantchicago.org

Food Loss and Waste

Yale Environment 360 produced a short documentary video on why we throw so much food
away.

• https://e360.yale.edu/features/the_big_waste_why_do_we_throw_away_so
_much_food

Genetically Modified Foods

WHO has an easy-to-follow and reasonably balanced summary of frequently asked ques-
tions on genetically modified foods.

• https://www.who.int/foodsafety/areas_work/food-technology/faq-genetically
-modified-food/en

Key Terms
agriculture An approach to land
management designed to grow
domesticated plants and raise domesticated
animals for food, fuel, and fiber.

aquaponics A soil-free method of growing
plants that incorporates hydroponics
with raising aquatic animals, like fish.

biomagnification The increasing
concentration of a toxin in an organism
due to eating other organisms
lower on the food chain.

community-supported agriculture
(CSA) A food distribution system in
which consumers purchase a “share”
in a local farm and receive regular
deliveries of farm products in return.

concentrated animal feeding operations
(CAFOs) According to the USDA, an
animal feeding operation with at least
1,000 “animal units” (1,000 cattle, 2,500
pigs, 55,000 turkeys, or 125,000 chickens)
confined for at least 45 days a year.

contour farming The practice of plowing
sideways across a hillside, following
the natural contour of the land.

cover crops Plants used to hold
soil in place and slow erosion.

crop rotation The practice of
planting different crops on the same
piece of land every few years.

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142

Bringing It All Together

desertification A process by which
land becomes increasingly arid
and unsuitable for farming.

fertilizers Natural or synthetic
substances that add nutrients to the soil,
thereby encouraging plant growth.

food security The situation in
which everyone has access to an
adequate and reliable food supply.

genetically modified organisms
(GMOs) Organisms that have had
their DNA modified in ways that would
not have been possible in nature.

genetic engineering The modification
of crops and animals by removing
genetic material from one organism and
combining it with the DNA of another.

Green Revolution A dramatic increase
in global agricultural production and
crop yields in the late 20th century due
to the industrialization of agriculture.

groundwater Water found underground
in the spaces in soil and rock.

hydroponics A soil-free method of growing
plants by suspending them with their roots
placed in a water–mineral nutrient solution.

industrial agriculture A form of
agriculture that mimics industrial systems
and relies heavily on mechanization,
fertilizers, pesticides, water, and
energy. Also known as industrialized
agriculture and factory farming.

integrated crop–livestock systems An
approach to farming in which a variety of
crops and animals are raised on the same
farm and animal wastes are used as fertilizer.
Sometimes referred to as agroecology,
permaculture, and low-input farming.

integrated pest management (IPM) An
approach to managing agricultural pests
with few or zero chemical pesticides.

intercropping See strip cropping.

irrigation The deliberate
diversion of water to crops.

low-till farming A farming technique
that uses minimal or shallow
tilling to minimize erosion.

monoculture farming The
cultivation of a single crop with the
intent of maximizing crop yields.

no-till farming A farming
technique that avoids plowing, or
tilling, to minimize erosion.

organic farming A form of agriculture
that complies with governmental
standards forbidding the use of synthetic
pesticides, fertilizers, hormones,
genetic modifications, and so on.

pesticides Substances intended to kill
organisms that are harmful to humans
or domesticated plants and animals;
includes insecticides, herbicides,
fungicides, and rodenticides.

pests Organisms that damage or
consume crops intended for human use.

polyculture farming The cultivation of
more than one (often compatible) plant
or animal species simultaneously.

precision agriculture A form
of agriculture that makes use of
technology to manage crops better
and use resources more efficiently.

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143

Bringing It All Together

soil The uppermost part of the Earth’s crust
that supports plant life; a mixture of sand
and gravel, silts and clays, dead organic
material, fauna and flora, water, and air.

soil erosion The displacement of
soil, often by water or wind.

soil fertility The ability of soil to
support plant life; influenced by nutrient
levels, soil pH, and soil structure.

soil horizon A horizontal layer
of soil with distinct qualities.

soil salinization The
accumulation of salts in soil.

strip cropping The practice of growing a
mix of different crops in the same area.

sustainable agriculture Farming
that meets our needs in ways that do
not undermine critical natural capital
systems and the ability of future
generations to meet their own needs.

terracing The practice of cutting into
steep terrain to create a series of steps
or platforms that can hold soil and
irrigation water in place to grow crops.

topsoil The upper portions of the A
horizon, where most living soil organisms
reside and where most plant roots are
established; often the basis for soil health.

traditional agriculture A form of
agriculture that uses primarily natural
and cyclical approaches to nutrient
management, pest control, animal
husbandry, and water management.

weathering The process of larger
rocks being worn away or broken
down into smaller particles by physical,
chemical, and biological forces.

weeds Plants that compete with crops.

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Lab Worksheet

Hypotheses:

Activity 1.

Activity 2.

10 Carolina Distance Learning

www.carolina.com/distancelearning 3

Activity 3.

Activity 4.

Observations/Data Tables

Data Table 1. Particle Size Distribution and Soil Type

Depth of Clay Layer (cm)

Depth of Silt Layer (cm)

Depth of Sand Layer (cm)

Total Depth (cm)

%

Clay

%

Silt

%

Sand

Soil Texture

Soil Sample A

Data Table 2. Determination of Soil Porosity

Time Taken for First Drop to Emerge from Column (s)

Sand Sample

Clay Sample

Soil Sample A

continued on next page


Data Table 3. pH Comparison of Soil Samples

Soil Sample A

Soil Sample B

(Location Description: )

pH

Data Table 4. Nitrogen, Phosphorus, and Potash Comparison in Soil Samples

Nitrogen

Phosphorus

Potash

Soil Sample A

Soil Sample B

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