Sustainable Living Guide Contributions, Part Two of Four:
Sustaining our Agricultural Resources
Instructions: Using the term that you have selected from the list provided in the classroom,
please complete the following three-paragraph essay. Write a minimum of 5 to 7 well-crafted,
original sentences per paragraph. In your response, you are expected to cite and reference, in
APA format, at least two outside sources in addition to the class text. The sources must be
credible (from experts in the field of study); at least one scholarly source (published in a peerreviewed academic journal) is strongly encouraged. Delete all instructions before submitting
your work to Waypoint.
Your Term: [type your term here]
[First Paragraph: Thoroughly define your term, using your own words to do so. In your
definition, be sure explain why the term is important to know. Be as specific as possible and
provide examples as necessary to support your ideas.]
[Second Paragraph: Discuss how the term affects living beings (including humans) and/or the
physical environment. Provide examples as needed.]
[Third Paragraph: Suggest two clear, specific actions that you and the other students
might take to promote environmental sustainability in relation to this term. Be creative and
concrete with your suggestions. For example, you might recommend supporting a particular
organization that is active in the field of your term. Explain exactly how those actions will aid in
safeguarding our environment in relation to your chosen term.]
References: Following your essay, list all references you cited, in APA format.
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Managing Our Population and Consumption
sculpies/iStock /Getty Images Plus
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.
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. The waste products
of our modern industrial society, including radioactive and other long-lived wastes, can be detected in even some of the most
remote locations of the globe. Our activities are fundamentally altering the chemical composition of the world’s atmosphere,
oceans, and soils. And we are now driving other species to extinction at rates that are 100 to 1,000 times greater than “normal” or
background rates of extinction.
It may come as some surprise then to consider that for much of human history our very survival as a species was in question. We
can divide human history into three broad periods: the preagricultural, the agricultural, and the industrial.
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
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).
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 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.
Based on data from “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-conten
t/uploads/2018/08/2018_WPDS.pdf (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.
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.
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.
Another important statistic that demographers focus on is the total fertility
rate (TFR). The TFR is the average number of children an individual woman
Karen Kasmauski /SuperStock
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 When calculating population change,
6 or 7. This was due to a number of factors. Since most were engaged in immigration and emigration must also
labor-intensive agriculture, large families were considered an asset. Because be considered.
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
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.
The link between fertility rates, the age structure of a population, and overall birth rates has led demographers to develop a visual
tool they call an age-structure pyramid. Age-structure pyramids, also called population pyramids, are a simple way to illustrate
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
Net migration rate
Rate of natural increase
Source: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content/uploads/2018/08/2018_WPDS.pdf (https://www.pr
Figure 3.2: Age-structure pyramids for Uganda, the
United States, and Japan
The age-structure pyramids for these three countries can tell us what
to expect of each country’s population growth.
Data from “International Data Base,” by US Census Bureau, 2018 (https://www.census.
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.
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.
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
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.
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
The four stages of demographic transition show the change in population growth that a country
experiences over time as it develops and industrializes.
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
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 almost the world
average. As a result, Mali’s population is growing at a rapid rate of 3.5% and will double every 20 years if the growth rate remains
the same. Senegal, also in West Africa, and Egypt in North Africa are moving from Phase 2 to Phase 3 of the demographic transition
as fertility rates and birth rates have begun to decline in recent years. India is now solidly in Phase 3 of the demographic transition,
since fertility rates have dropped to 2.3 and birth rates to 20 per 1,000. However, because India has a relatively young population—
the age-structure pyramid is wider at the bottom—there is some built-in demographic momentum. As a result, India, already the
second most populous country in the world after China, will become the most populous around the year 2022. The Southeast Asian
nation of Malaysia is further along in the demographic transition than India. Meanwhile, countries like Denmark and South Korea
are clearly already in Phase 4, a situation characterized by low fertility, low birth and death rates, and stable or even declining
Table 3.2: Demographic data for countries in different phases
Rate of natural increase
Demographic transition phase
Sources: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content/uploads/2018/08/2018_WPDS.pdf (https://www.pr
b.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/informationGat
eway.php (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
Figure 3.4: World population, 1950–2100
Demographers expect much of the world’s population growth to come from developing countries, as the
population in more developed countries stabilizes or even declines.
Data from “World Population Prospects: The 2017 Revision,” DVD edition, by United Nations, Department of Economic and Social
Affairs, Population Division, 2017 (https://population.un.org/wpp/Download/Standard/Population (https://population.un.org/
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.
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.
Data from UNESCO Institute for Statistics, Data Center, n.d. (http://data.uis.unesco.org (http://data.uis.unesco.org) ).
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 that these actions would
increase women’s status in society and result in greater empowerment of
women in making decisions about their own fertility.
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
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
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.
Figure 3.6: Female employment, CO2 emissions, and fertility
Total fertility rates plotted against female employment (a) and CO2 emissions (b).
Data from “Children per Woman (Total Fertility Rate),” by Gapminder, n.d. (http://gapm.io/dtfr (http://gapm.io/dtfr) );
“ILOSTAT,” by International Labour Organization, 2019 (https://www.ilo.org/ilostat (https://www.ilo.org/ilostat) ); “FossilFuel CO2 Emissions,” by Carbon Dioxide Information Analysis Center, 2017 (http://cdiac.ornl.gov/trends/emis/meth_reg.h
tml (http://cdiac.ornl.gov/trends/emis/meth_reg.html) ).
We often expect to see correlated data when there is a cause-and-effect relationship at play. For example, our female
employment and fertility data are correlated, and there is also a strong theory for how female employment might cause a
decrease in a region’s fertility rates. More women working means that more women are financially independent. With more
financial freedom, more women might choose to delay or avoid getting married and having children.
This cause-and-effect relationship can also be supported with studies that have explored female employment in greater
depth. In one recent example, researchers studied rural communities in Senegal. By surveying them about their family sizes
and lifestyle choices, the researchers found that the relationship held up (Van den Broeck & Maertens, 2015).
When we have correlated data and supporting evidence of a cause-and-effect relationship, we might conclude there is a
causal relationship between the two measurements in a data set. Causal relationships can be very useful from a policy
standpoint. If we determined that a causal relationship exists between female employment and fertility, we might develop
job-training programs and fair hiring regulations to exploit this relationship.
It is critical to realize that correlated data does not necessarily imply a causal relationship. As researchers, we have to
remember the mantra “correlation is not causation” so that we do not draw conclusions based on relationships that do not
exist. On the second chart, it appears that the countries with greater emissions have lower fertility rates. However, there is
no obvious explanation for how CO2 emissions might impact reproduction. Countries often undergo changes that impact
both CO2 emissions and fertility rates at the same time, but this does not mean that CO2 emissions are causing reproductive
changes. As a result, we have no reason to believe that we can change fertility rates by encouraging people to burn more
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.
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, sponsoring condom balloon-blowing contests, and
painting birth control advertisements on buses, billboards, and even the
sides of water buffalo. The PDA used humor to encourage a more open
discussion in polite Thai society about the use of contraception. 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.
Jerry Redfern/LightRocket/Getty Images
The Population and Community Development
Association in Thailand aims to educate the
population about family planning by making
contraception more accessible and encouraging
Learn More: The Condom King
Watch the following video to see Mechai Viravaidya in action and hear his thoughts on his approach to population policy in
The Condom Delivering the Goods
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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.
monkeybusinessimages/iStock /Getty Images Plus
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
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.
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.
andresr/E+/Getty Images Plus
As more consumers have become aware of these issues, the coffee
industry has responded with new products. Fair trade coffees try to
ensure that growers get paid adequately for their coffee beans, and
more retailers are offering shade-grown varieties that can result in less
environmental destruction. Several organizations now provide
certifications to help consumers identify these better alternatives. The
Smithsonian Bird Friendly certification ensures that forests are
protected during coffee production. The Rainforest Alliance certification
indicates that growing practices and compensation both meet strict
sustainability standards. Fair trade options might have a Fair Trade USA
symbol, and many organic options are identified with the familiar USDA
stamp from the U.S. Department of Agriculture.
A coffee plantation in Colombia. Fair trade
coffee growers ensure that their workers are
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 (https://worldma
pper.org/maps/coffee-production-2014/) and the Worldmapper map on global coffee consumption (https://worldmapper.or
g/maps/coffee-consumption-2014/) . 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?
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
Learn More: IPAT
This animated video connects IPAT to the concept of the ecological, or environmental, footprint. As you will read in the next
section, some might consider the environmental footprint measure to be the outcome of the IPAT formula.
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
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.
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.
Lee Lorenz/Cartoon Collections
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 (http://data.footprintn
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).
Table 3.3: Environmental footprint and population data for 25 countries
Sources: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content/uploads/2018/08/2018_WPDS.pdf (https://www.pr
b.org/wp-content/uploads/2018/08/2018_WPDS.pdf) ); “Ecological Footprint Explorer,” by Global Footprint Network, 2018 (http://data.footprintnetwork.org/#/compareCount
ries (http://data.footprintnetwork.org/#/compareCountries) ).
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
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 Fo
otprint Explorer (http://data.footprintnetwork.org/#/) .
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 htt
ps://worldmapper.org/ (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 (https://worldmapper.org) and
have a look at the world in a whole new way.
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
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.
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?
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.
Population Policy and Fertility Control
There are many good TED Talks on the subject of population and the environment, but here are three that are definitely worth
watching, including one on Thailand’s “Mr. Condom.”
Hans Rosling: Global Population Growth, Box by Box: https://www.youtube.com/watch?v=fTznEIZRkLg (https://www.yo
Hans Rosling: The Good News of the Decade?: https://www.youtube.com/watch?v=OT9poH_D2Iw (https://www.youtub
Mechai Viravaidya: How Mr. Condom Made Thailand a Better Place: https://www.youtube.com/watch?v=EL9TBKSdHX
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.
These links provide a good background on China’s one-child policy and how that policy has recently begun to change.
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
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.
A graphical illustration of how a specific population is broken down by age and gender. Also known as a population pyramid.
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.
The tendency for a population to continue growing even after its fertility rate declines, due to the number of young people in the
A model used by demographers to explain and understand the relationship between changing birth rates, death rates, and total
The statistical study of human population change.
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.
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.
The act of people moving out of a given population.
The act of people moving into a given population.
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.
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.
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
rate of natural increase
The rate of population growth; in a given population, birth rates minus death rates, excluding immigration and emigration.
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).
Sustaining Our Agricultural Resources
branex/iStock/Getty Images Plus
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.
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
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.
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.
At the same time, scientific advances in fields like chemistry, plant genetics,
and soil science boosted crop productivity per unit of land. In particular,
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breakthroughs in the production of synthetic fertilizer in the late 19th
century, especially in the production of nitrogen fertilizer on an industrial Early farming machines, such as the steamscale, enabled continued increases in food production. Fertilizers are driven thresher pictured here, changed
substances that add nutrients to the soil, thereby encouraging plant growth. agricultural practices during the
While traditional farmers had long made use of available organic material Industrial Revolution.
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.
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
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, herbicides, water, and energy for equipment to grow
that crop. In the United States and other developed countries, much of the
production 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.
fotokostic/iStock/Getty Images Plus
While traditional farms grow a variety of crops,
industrial farms almost always raise one single
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.
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
Focuses on maximizing yield (monoculture)
Focuses on a diversity of species and products (polyculture)
Results in higher rates of soil erosion and land
Maintains soil quality and long-term soil health
Relies on synthetic fertilizers and chemical pesticides
Relies on organic fertilizers and natural approaches to pest
Requires heavy use of irrigated water
Minimizes water use by matching crops to regional climate
Heavily uses fossil fuels
Uses minimal fossil fuels
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:
mineral matter (sand, gravel, silt, and clay)
dead organic material (e.g., decaying leaves and plant matter)
soil fauna and flora (living bacteria, worms, fungi, and insects)
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.
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 to the soil. Likewise, when plants,
animals, and other living organisms die and drop to the ground, decomposers and detritivores break them down and incorporate
that organic material into the soil.
The processes of weathering and deposition and decomposition are influenced mainly by climate, topography, and time, allowing
soils to form faster in some locations than in others. For example, an inch of new soil can take 50 to 100 years to develop in a
healthy grassland ecosystem, whereas the same inch of soil might take 100,000 years to develop in a desert or tundra ecosystem.
Soil scientists recognize that soil develops into distinct layers, and they refer to each of these layers as a soil horizon. For our
purposes, we can consider five different soil horizons: O, A, B, C, and D. The O (organic) horizon is at the very top and is made up of
decomposing plant matter and animal waste that is sometimes referred to as humus. Below this is the A horizon, which is made up
of organic matter and mineral particles.
The A horizon is where most of the living soil organisms reside, and the upper portions of the A horizon are generally referred to as
topsoil. Most plant roots are established in the A horizon, which is why soil health is often based on the condition of topsoil.
Below the A horizon is the B horizon, also known as subsoil, and below that is the C horizon, which consists of weathered rock.
Finally, the D horizon is known as bedrock (see Figure 4.1).
Figure 4.1: Soil horizons
Farmers are most concerned with the fertility of the topsoil, or A horizon.
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