SOLUTION: SCI 207 Ashford University Organic Farming Discussion

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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Population Change Through Time
Section 3.1
At 2 minutes before midnight on Sunday, October 30, 2011, a 5.5-pound baby girl named Danica 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 Division 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 Philippines” 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, increasing 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 population 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 influence 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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Population Change Through Time
Section 3.1
The waste products of our modern industrial society, including radioactive and other longlived 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 survival 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 population of the United States today. Despite the advances brought on by the agricultural revolution, 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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Population Change Through Time
Section 3.1
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 billion 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.
Preagricultural
period
Agricultural
period
Industrial
period
7.7 billion
7 billion
7
6 billion
6
5
4 billion
4
3
0
8000
BCE
5000
BCE
100
CE
1250
CE
1400
CE
1.1 billion
470 million
1600 1650 1850
CE CE
CE
2019
5 million 50 million
2 billion
1999
2011
1
350 million
400 million
545 million
300 million
1974
2
1930
Human population (billions)
8
Year
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).
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 billion 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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Demographics
Section 3.2
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 demographers call the rate of natural increase—birth rates minus death rates, excluding immigration 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 typically 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, demographers determine the net migration rate
as the difference between immigration and
emigration per 1,000 people in a given population over the course of 1 year.
Karen Kasmauski /SuperStock
When calculating population change,
immigration and emigration must also
be considered.
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Demographics
Section 3.2
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 childbearing years (currently considered to range from age 15 to 49). In preindustrial societies, fertility 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. Agestructure pyramids, also called population pyramids, are a simple way to illustrate graphically 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)
World
19
7
Uganda
United States
Japan
41
12
8
9
9
11
TFR
Net migration
rate
(per 1,000)
Rate of natural
increase
(percentage)
2.4
N/A
1.2
1.8
3
5.4
1.4
–1
3.2
1
–0.3
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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Demographics
Section 3.2
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.
Uganda – 2018
Male
Female
100+
95–99
90–94
85–89
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
05–09
00–04
4.8
4.0
3.2
2.4
1.6
Population (in millions)
0.8
0
0
Age Group
0.8
1.6
2.4
3.2
4.0
Population (in millions)
United States – 2018
Male
4.8
Female
100+
95–99
90–94
85–89
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
05–09
00–04
18
15
12
9
6
3
Population (in millions)
0
0
3
Age Group
6
9
12
15
Japan – 2018
Male
18
Population (in millions)
Female
100+
95–99
90–94
85–89
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
05–09
00–04
6
5
4
3
2
Population (in millions)
1
0
0
Age Group
1
2
3
4
5
6
Population (in millions)
Data from “International Data Base,” by US Census Bureau, 2018 (https://www.census.gov/data-tools/demo/idb/informationGateway.php).
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Demographics
Section 3.2
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 demographic 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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The Demographic Transition
Section 3.3
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 billion 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
Births and deaths (per thousand per year)
The four stages of demographic transition show the change in population growth that a country
experiences over time as it develops and industrializes.
50
Total population
Death rate
Birth rate
40
30
20
10
0
Phase 1:
Preindustrial
Phase 2:
Transitional
Phase 3:
Industrial
Phase 4:
Postindustrial
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The Demographic Transition
Section 3.3
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 demographic 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 countries 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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The Demographic Transition
Section 3.3
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 agestructure 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
World
19
7
2.4
1.2
3/4
Senegal
33
2.7
2/3
India
20
1.4
3
Mali
Egypt
Malaysia
Denmark
45
10
6.0
3.5
27
6
3.4
2.1
16
South Korea
11
7
6
6
5
9
6
4.6
2.3
1.9
1.8
1.1
Demographic
transition
phase
2
2/3
1.1
3/4
0.1
4
0.2
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 developing countries move through the demographic transition. The speed of a country’s demographic 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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Population Policy and Fertility Control
Section 3.4
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.
12
11
10
9
Billions
8
7
6
5
4
3
Less developed countries
2
1
0
More developed countries
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100
Year
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).
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 population 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.
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Population Policy and Fertility Control
Section 3.4
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, combined 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 education 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 secondary 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.
10
Number of children per woman
9
8
7
6
5
4
3
2
1
0
20%
40%
60%
80%
100%
Percent enrollment in secondary school
Data from UNESCO Institute for Statistics, Data Center, n.d. (http://data.uis.unesco.org).
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Population Policy and Fertility Control
Section 3.4
Early Population Policies
As discussed earlier, by 1950 most developing countries were still in Phase 1 or 2 of the demographic transition. In the decades that followed, rapid improvements in medicine, sanitation,
food supply, and water quality dramatically lowered death rates in these countries and triggered 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 sterilizations—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 million 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 recommendations 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 planning 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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Population Policy and Fertility Control
Section 3.4
that these actions would increase women’s status in society and result in greater empowerment of women in making decisions about their own fertility.
Compared with earlier population policies, the ICPD recommendations emphasized indirect 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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Population Policy and Fertility Control
Section 3.4
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).
(a)
10
Total fertility (births per woman)
9
8
7
6
5
4
3
2
1
0
20%
40%
60%
80%
Female salaried workers (% of females employed)
0.1
1
10
CO2 emissions (metric tons per person)
100%
(b)
10
Total fertility (births per woman)
9
8
7
6
5
4
3
2
1
0
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).
(continued)
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Population Policy and Fertility Control
Section 3.4
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 jobtraining 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.
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 environment. More and more observers are pointing to high material consumption rates in developed countries as the greatest threat to the global environment, as opposed to high population 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.
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Case Study: Population Policies in China and Thailand
Section 3.5
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 punishments 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 exceptions 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 abortions and mass sterilizations such as those that occurred in India. In 1991, 12.5 million Chinese citizens underwent sterilization, oftentimes against their will and under threat of violence 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 perhaps 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 increasing 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, sponJerry Redfern/LightRocket/Getty Images
soring condom balloon-blowing contests,
and painting birth control advertisements The Population and Community Development
on buses, billboards, and even the sides Association in Thailand aims to educate
of water buffalo. The PDA used humor to the population about family planning by
encourage a more open discussion in polite making contraception more accessible and
Thai society about the use of contraception. encouraging positive discussions.
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Population Growth and Material Consumption
Section 3.6
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 obvious. More people consume more energy, food, water, and resources. More people also generate 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 environmental 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 fellow 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 equation called the IPAT formula (pronounced i-pat) to illustrate this argument. The I in the formula 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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Population Growth and Material Consumption
monkeybusinessimages/iStock /Getty Images Plus
Section 3.6
stockimagesbank/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.
While poorer countries with high rates of population growth may be impacting the environment through the P factor, wealthy countries have a larger impact through the A factor 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 individuals 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.
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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Population Growth and Material Consumption
Section 3.6
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
andresr/E+/Getty Images Plus trade options might have a Fair Trade
A coffee plantation in Colombia. Fair trade
USA symbol, and many organic options
are identified with the familiar USDA
coffee growers ensure that their workers are
stamp from the U.S. Department of
paid adequately.
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?
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Population Growth and Material Consumption
Section 3.6
The IPAT formula helps us consider and analyze the wide gap that exists in resource consumption 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 interrelate 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 environmental 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 environment. 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 environmental 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, livestock/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 supply 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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Population Growth and Material Consumption
Section 3.6
Lee Lorenz/Cartoon Collections
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 populations, 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, population 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.
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Population Growth and Material Consumption
Section 3.6
Table 3.3: Environmental footprint and population data for 25 countries
Country
Environmental
footprint
(ha/
person)
Bio­
capacity
(ha/
person)
Total environmental
footprint
(million ha)
Total biocapacity
(million
ha)
Ecological
deficit or
reserve
(million
ha)
World
2.75
1.63
20,509
12,169
–8,340
0.41
137
66
–71
0.48
44
20
–24
Haiti
0.68
0.32
Zambia
0.95
1.88
Bangladesh
Uganda
1.06
Nepal
1.07
India
1.17
Tanzania
Philippines
Cuba
El Salvador
Vietnam
Peru
0.84
1.22
1.33
1.78
2.06
2.12
2.24
0.56
7
4
16
31
31
16
–80
0.6
13
3.68
166.4
3.2
44.1
1.4
57
201
1.4
2.3
–15
137
1.02
2.1
3.1
0.55
20
7,621.4
5.2
–981
0.81
1.2
15
566
57
2.4
3.0
1,547
68
Total
population
(millions)
–3
0.43
1.02
TFR
Population
growth
rate
5.4
2.3
1.7
1.5
107.0
1.3
6.5
9
–11
1.6
0.2
96
–105
2.1
0.9
82
–89
71
117
584
–9
2.3
29.7
1,371.3
5.2
4
17.7
1.4
–11
2.7
10.8
3.3
59.1
11.1
94.7
46
2.4
1.4
32.2
1,807
1,223
1.7
0.8
209.4
Thailand
2.49
1.18
171
South
Africa
3.15
0.96
176
China
3.62
0.96
5,195
1,374
–3,821
1.8
0.5
1,393.8
Japan
4.49
0.58
574
74
–500
1.4
–0.3
126.5
14
–187
2.4
1.4
33.4
Brazil
Malaysia
Germany
Saudi
Arabia
2.81
3.92
4.84
6.23
8.7
2.26
1.62
0.42
122
54
70
397
133
201
–122
–52
–264
1.5
2.4
1.9
1.6
Australia
6.64
12.27
160
296
136
1.7
Canada
7.74
15.12
3.65
281
2,611
549
1,175
268
–1,436
1.5
Luxembourg
12.91
1.24
7
0.7
–6
Denmark
United
States
6.8
8.1
4.17
39
23
–16
0.2
1.2
1.1
–0.2
66.2
57.7
32.5
82.8
0.6
24.1
0.3
37.2
1.8
0.2
1.8
0.3
328.0
0.3
0.6
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); “Ecological Footprint Explorer,” by Global Footprint Network, 2018 (http://data
.footprintnetwork.org/#/compareCountries).
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5.8
Population Growth and Material Consumption
Section 3.6
On average, across the entire world, each person has an environmental footprint of 2.75 hectares (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 environmental footprint per person is over 7 hectares (or 17.3 acres).
While there are reasons to be concerned, from an environmental standpoint, about countries 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. Comparing 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 countries 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. Australia 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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Bringing It All Together
Global Consequences
The GFN estimates that over 80% of the world’s population lives in countries that are running 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 consumption 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 important 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 environmental management.
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Bringing It All Together
Additional Resources
Demographics
There are a number of online sources that allow you to see how world population is changing 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? Different methods? Different assumptions? Different sources of data?
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https://www.census.gov/popclock/
https://www.worldometers.info/world-population/
https://www.unfpa.org/data/world-population-dashboard
•
•
•

PRB

https://www.un.org/en/development/desa/population/index.asp
https://www.census.gov/topics/population.html
You can find a lot of basic demographic data and other useful information about population
trends and issues at these websites.
The Demographic Transition
This website provides an interactive lab/simulator that allows you to change the demographic 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.”
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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 remembered 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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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 (“Population Campaigns”) and how material consumption differs among families in different countries (“Material World”).
•
https://www.pbs.org/wgbh/nova/worldbalance
•
https://www.unfpa.org/sites/default/files/sowp/downloads/The_State_of_World
_Population_2016_-_English.pdf
The United Nations Population Fund published an interesting report that looks at future
population trends from the perspective of a 10-year-old girl.
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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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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The Origins and History of Agriculture
Section 4.1
In October 2018 the scientific journal Nature published a major research report that presented a troubling picture of the future of food, agriculture, and the environment (Springmann 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 population 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 rising incomes in countries like China result in more demand for meat and other animal proteins, 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 supplies. 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 agriculture 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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The Origins and History of Agriculture
Section 4.1
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 technological 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 cultivation. 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 beginning 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 disease, as well as social collapse, as human numbers 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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The Origins and History of Agriculture
Section 4.1
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 substances 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 without 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 produced 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 dramatic. 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 agriculture. The impressive increases in yield achieved in the first few decades of the Green Revolution 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 population 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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Characteristics of Industrial Agriculture
Section 4.2
4.2 Characteristics of Industrial Agriculture
The Green Revolution ushered in what is now known as industrial agriculture. These industrialized 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 compare 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 agriculture 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 agriculture 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,
fotokostic/iStock/Getty Images Plus
herbicides, water, and energy for equipment
While traditional farms grow a variety of
to grow that crop. In the United States and
crops, industrial farms almost always raise one
other developed countries, much of the prosingle crop.
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.
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Characteristics of Industrial Agriculture
Section 4.2
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 produce 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 phenomenon 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)
Relies on synthetic fertilizers and chemical
pesticides
Relies on organic fertilizers and natural approaches
to pest management
Results in higher rates of soil erosion and land
degradation
Requires heavy use of irrigated water
Heavily uses fossil fuels
Maintains soil quality and long-term soil health
Minimizes water use by matching crops to regional
climate
Uses minimal fossil fuels
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The Importance of Soil
Section 4.3
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 agriculture 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. However, 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 living 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, centipedes, 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 machinery, 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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The Importance of Soil
Section 4.3
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: weathering 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 particles 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…
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