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Chapter Introduction

Slum area (bottom) in Mumbai, India

ZUMA Press, Inc./Alamy Stock Photo

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Core Case StudyPlanet Earth: Population 7.6 Billion

Learning Objectives

· LO 6.1Describe the growth of the human population in terms of numbers of years between doublings.

· LO 6.2List three major factors that account for the rapid rise of the human population.

It took about 200,000 years for the human population to reach an estimated 2 billion. It took less than 50 years to add the second 2 billion people (by about 1974), and 25 years to add the third 2 billion (by 1999). Nineteen years later, in 2018, the earth had 7.6 billion people. In 2018, the three most populous countries, in order, were China with 1.39 billion people (Figure 6.1), India with 1.37 billion people, and the United States with 328 million people. The United Nations projects that the world’s population will increase to 9.9 billion by 2050—an increase of 2.3 billion people.

Figure 6.1

This crowded street is located in Shanghai, China, the world’s most populous country.

TonyV3112/ Shutterstock.com

Many scientists disagree and contend that the current exponential growth of the human population (see Figure 1.12) is unsustainable because as our population and economies grow, we use more of the earth’s natural resources and our ecological footprints grow. As a result, we degrade the natural capital that keeps us alive and supports our lifestyles and economies.

According to demographers, or population experts, three major factors account for the rapid rise of the human population. First, the emergence of early and modern agriculture about 10,000 years ago increased food production. Second, additional technologies helped humans expand into almost all of the planet’s climate zones and habitats (see Figure 1.9). Third, death rates dropped sharply with improved sanitation and health care and the development of antibiotics and vaccines to control infectious diseases.

What is a sustainable level for the human population? Population experts have made low, medium, and high projections of the human population size by the end of this century (see Figure 1.12). No one knows whether, or for how long, any of these population sizes are sustainable.

In this chapter, we examine trends, environmental impacts, and ways to deal with human population growth and decline.

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6.1aHuman Population Growth

For most of history, the human population grew slowly (see Figure 1.12, left part of curve). However, it has grown rapidly for the last 200 years, resulting in the characteristic J-curve of exponential growth (Figure 1.12, right part of curve).

Demographers, or population experts, recognize three important trends related to the current size, growth rate, and distribution of the human population. First, the rate of population growth decreased in most years since 1965, but the world’s population grew at a rate of 1.20% in 2018 (Figure 6.2). This may not seem like much. However, in 2018 this growth rate added about 91 million people to the population—an average of 249,000 more people every day.

Figure 6.2

Global human population size compared with population growth rate, 1950–2018, with projection to 2050 (in blue).

Critical Thinking:

1. While the annual growth rate of world population has generally dropped since the 1960s, how do you explain the continued growth of the overall population?

(Compiled by the authors using data from United Nations Population Division, U.S. Census Bureau, and Population Reference Bureau.)

2.3 Billion

Projected increase in the world’s population between 2018 and 2050

Second, human population growth is unevenly distributed and this pattern is expected to continue (Figure 6.3). About 96% of the 91 million new arrivals on the planet in 2018 were added to the world’s less-developed countries. The other 4% were added to the more developed countries.

Figure 6.3

Most of the world’s population growth between 1950 and 2018 took place in the world’s less-developed countries. This gap is projected to increase between 2018 and 2050.

(Compiled by the authors using data from United Nations Population Division and Population Reference Bureau.)

At least 95% of the 2.3 billion people projected to be added to the world’s population between 2018 and 2050 will be born into the less-developed countries (Figure 6.3). Most of these countries are not equipped to deal with the pressures of rapid population growth.

Third, people have moved in large numbers from rural areas to urban areas. In 2018, 55% of the world’s people lived in urban areas, and this percentage is increasing. Most of these urban dwellers live in less-developed countries where resources for dealing with rapidly growing populations are limited

Scientists and other analysts have long pondered the question: How long can the human population continue to grow while sidestepping many of the factors that sooner or later limit the growth of any population? These experts disagree over how many people the earth can support indefinitely. So far, advances in food production and health care have prevented sharp population declines, but there is extensive and growing evidence that human activities are depleting and degrading much of the earth’s irreplaceable natural capital.

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6.1bHow Long Can the Human Population Keep Growing?

Are there physical limits to human population growth and economic growth on a finite planet? Some say yes. Others say no.

This debate has been going on since 1798 when Thomas Malthus, a British economist, hypothesized that the human population tends to grow exponentially, while food supplies tend to increase more slowly at a linear rate. However, food production has grown at an exponential rate instead of at a linear rate because of technological advances in industrialized food production.

One view is that we have already exceeded some of those limits, with too many people collectively degrading the earth’s life-support system. To some analysts, the key problem is the large and rapidly growing number of people in less-developed countries, which have 84% of the world’s population. To others, the key factor is overconsumption in affluent, more-developed countries with high rates of resource use per person.

Another view of population growth is that technology has allowed us to overcome the environmental limits that all populations of other species face. According to this view, technological advances have increased the earth’s carrying capacity for the human species. Some analysts point out that average life expectancy in most of the world has been steadily rising despite warnings from some environmental scientists that we are seriously degrading our life-support system.

These analysts argue that because of our technological ingenuity, there are few, if any, limits to human population growth and resource use per person. They believe that we can continue increasing economic growth and avoid serious damage to our life-support systems by making technological advances in areas such as food production and medicine, and by finding substitutes for resources that we are depleting. They see no need to slow the world’s population growth or resource consumption.

Proponents of slowing or stopping population growth point out that currently, we are failing to provide the basic necessities for about 815 million people who struggle to survive on the equivalent of about $1.90 per day and the 2.1 billion people struggling to live on $3.10 or less. This raises a serious question: How will we meet the basic needs of the additional 2.3 billion people projected to be added mostly to less-developed countries between 2018 and 2050?

Proponents of slowing population growth also warn of two potentially serious consequences if we do not sharply lower birth rates. First, death rates could increase because of declining health and environmental conditions and increasing social disruption in some areas, as is happening today in parts of Africa. A worst-case scenario for such a trend is a crash of the human population from more than 7 billion to a more sustainable level of 4 billion or perhaps as low as 2 billion. Second, resource use and degradation of normally renewable resources may intensify as more consumers increase their already large ecological footprints in more-developed countries and in rapidly developing countries such as China, India, and Brazil.

As the human population grows, so does the global human ecological footprint (see Figure 1.9), and the bigger this footprint, the higher the overall impact of humanity on the earth’s natural capital. The 2005 Millennium Ecosystem Assessment concluded that human activities have degraded about 60% of the earth’s ecosystem services. Despite advances in food production and health care that have prevented widespread population declines, we are depleting and degrading much of the earth’s natural capital (see Figure 1.3 and Figure 6.4). We can get away with this for a while, because the earth’s life-support system is resilient. However, such disturbances could reach various tipping points beyond which there could be damaging and long-lasting change (Science Focus 3.2).

Figure 6.4

Human activities have altered the natural systems that sustain our lives and economies in at least eight major ways to meet the increasing needs and wants of the growing human population.

Critical Thinking:

1. In your daily living, do you think you contribute directly or indirectly to any of these harmful environmental impacts? Which ones? Explain.

Top: Dirk Ercken/ Shutterstock.com. Center: Fulcanelli/ Shutterstock.com. Bottom: Werner Stoffberg/ Shutterstock.com.

Some say that asking how many people the earth can support indefinitely is asking the wrong question. Instead, they call for us to estimate the planet’s  cultural carrying capacity —the maximum number of people who could live in reasonable freedom and comfort indefinitely, without decreasing the ability of the earth to sustain future generations.

Critical Thinking

1. Do you think there are environmental limits to human population growth? Explain. If so, how close do you think we are to such limits? Explain.

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6.2aThe Human Population Can Grow, Decline, or Stabilize

The basics of global human population change are simple. When there are more births than deaths, the human population increases; when there are more deaths than births, it decreases. When the number of births equals the number of deaths, population size does not change.

Instead of using the total numbers of births and deaths per year, demographers use the  crude birth rate  (the number of live births per 1,000 people in a population in a given year) and the  crude death rate  (the number of deaths per 1,000 people in a population in a given year).

The human population in a particular area grows or declines through the interplay of three factors: births (fertility), deaths (mortality), and migration. We can calculate the  population change  of an area by subtracting the number of people leaving a population (through death and emigration) from the number entering it (through birth and immigration) during a year:

When births plus immigration exceed deaths plus emigration, a population grows; when the reverse is true, a population declines.

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6.2bFertility Rates

Demographers distinguish between two types of fertility rates. One is the  replacement-level fertility rate : the average number of children that couples in a population must bear to replace themselves. It is slightly higher than two children per couple (typically 2.1) because some children die before reaching their reproductive years, especially in the world’s poorest countries.

If we were to reach a global replacement-level fertility rate of 2.1 tomorrow, would it bring an immediate halt to human population growth? No, because there is a large number of potential mothers under age 15 who will be moving into their reproductive years.

The second type of fertility rate is the  total fertility rate (TFR) . It is the average number of children born to the women of childbearing age in a population. It is a key factor affecting human population growth and size.

Between 1955 and 2018, the global TFR dropped from 5.0 to 2.4. Those who support slowing the world’s population growth view this as good news. However, to eventually halt human population growth, the global TFR must drop to and remain at the fertility replacement level of 2.1—the rate necessary for replacing both parents after considering infant mortality.

With a TFR of 4.6, Africa’s population is growing more than twice as fast as any other continent and is projected to more than double from 1.3 billion in 2018 to 2.6 billion in 2050 and continue to grow. By the end of this century, Africa is projected to have 40% of the world’s people. Africa is also the world’s poorest continent.

Estimates of any population’s future numbers can vary considerably, depending mostly on TFR projections. Demographers also have to make assumptions about death rates, migration, and a number of other variables. If their assumptions are wrong, their population forecasts can be inaccurate (Science Focus 6.1).

Science Focus 6.1

Projecting Population Change

Estimates of the human population size in 2050 range from 7.8 billion to 10.8 billion people—a difference of 3 billion. The range of estimates varies because many factors affect birth rates and TFRs.

First, demographers have to determine the reliability of current population estimates. While many more-developed countries such as the United States have reliable estimates of their population size, most countries do not. Some countries deliberately inflate or deflate the numbers for economic or political purposes.

Second, demographers make assumptions about trends in fertility. They might assume that fertility is declining by a certain percentage per year. If this estimate is off by a few percentage points, the resulting percentage increase in population can be magnified over a number of years and be quite different from the projected population size increase.

For example, United Nation (UN) demographers assumed that Kenya’s fertility rate would decline. Based on that, in 2002 they projected that Kenya’s total population would be 44 million by 2050. In reality, the fertility rate rose sharply. As a result, in 2018 the UN revised its projection for Kenya’s population in 2050 to 96 million, which was 140% higher than its earlier projection.

Third, population projections are made by a variety of organizations. UN projections are often cited, but the U.S. Census Bureau, the International Institute for Applied Systems Analysis (IIASA), and the U.S. Population Reference Bureau also make projections. Their projections vary because they use differing sets of data and differing methods (Figure 6.A).

Figure 6.A

World population projections to 2050 from three different organizations: the UN, the U.S. Census Bureau, and IIASA. Note that the uppermost, middle, and lowermost curves of these five projections are all from the UN, each assuming a different level of fertility.

Data Analysis:

1. What are the ranges (differences between the lowest and highest) in these projections for 2030, 2040, and 2050?

(Compiled by the authors using data from United Nations, U.S. Census Bureau, and IIASA.)

Critical Thinking

1. If you were in charge of the world and making decisions about resource use based on population projections, which of the projections in Figure 6.A would you rely on? Explain.

Case Study

Between 1900 and 2018, the U.S. population grew from 76 million to 328 million. This happened despite oscillations in the country’s TFR (Figure 6.5) and population growth rate.

Figure 6.5

Total fertility rates for the United States between 1917 and 2018.

Critical Thinking:

1. The U.S. fertility rate has declined and remained at or below replacement levels since 1972. So why is the population of the United States still increasing?

(Compiled by the authors using data from Population Reference Bureau and U.S. Census Bureau.)

During the period of high birth rates between 1946 and 1964, known as the baby boom, 79 million people were added to the U.S. population. At the peak of the baby boom in 1957, the average TFR was 3.7 children per woman. In most years since 1972, it has been at or below 2.1 children per woman. In 2018, it was 1.8 compared to a global TFR of 2.4. A key factor in this decline is an increase in the average age of a woman at the time when her first child was born.

The drop in the TFR has slowed the rate of population growth in the United States, but the country’s population is still growing. In 2018, about 1.8 million people were added to the U.S. population—1 million due to the fact that there were more births than deaths and 800,000 due to legal immigration.

Since 1820, the United States has admitted almost twice as many legal immigrants and refugees as all other countries combined. The number of legal immigrants (including refugees) has varied during different periods because of changes in immigration laws and rates of economic growth (Figure 6.6).

Figure 6.6

Legal immigration to the United States, 1820–2013 (the last year for which data are available). The large increase in immigration since 1989 resulted mostly from the Immigration Reform and Control Act of 1986, which granted legal status to certain illegal immigrants who could show they had been living in the country prior to January 1, 1982.

(Compiled by the authors using data from U.S. Immigration and Naturalization Service, the Immigration Policy Institute, and the Pew Hispanic Center.)

Since 1965, nearly 59 million people have legally immigrated to the United States, most of them from Latin America and Asia, with the government giving preferences for those with technical training or with family members of U.S. citizens. A 2015 study by the U.S. Census Bureau noted that in 2013, China surpassed Mexico as the largest source of new U.S. immigrants.

According to population experts, the country’s influx of immigrants has made the country more culturally diverse and has increased economic growth as these citizens worked and started businesses. The United States has an estimated 10.7 million illegal immigrants. There is controversy over whether to deport those who can be found or to allow these individuals to meet strict criteria for becoming U.S. citizens. Since 2005, the flow of illegal immigrants into the country has been dropping, according to the Pew Research Center.

In addition to the fourfold increase in population since 1900, some amazing changes in lifestyles took place in the United States during the 20th century (Figure 6.7), which led to Americans living longer. Along with this came dramatic increases in per capita resource use and much larger total and per capita ecological footprints.

Figure 6.7

Some major changes that took place in the United States between 1900 and 2000.

(Compiled by the authors using data from U.S. Census Bureau and Department of Commerce.)

62 Million

Projected increase in the U.S. population between 2018 and 2050

The U.S. Census Bureau projects that between 2018 and 2050, the U.S. population will likely grow from 328 million to 390 million—an increase of 62 million people. Because of a high per-person rate of resource use and the resulting waste and pollution, each addition to the U.S. population has an enormous environmental impact.

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6.2cFactors That Affect Birth and Fertility Rates

Many factors affect a country’s average birth rate and total fertility rate (TFR). One is the importance of children as a part of the labor force, especially in less-developed countries. Many poor couples in those countries struggle to survive on less than $3.10 a day and some on less than $1.90 a day. Some of these couples have a large number of children to help them haul drinking water, gather wood for heating and cooking, and grow or find food. Worldwide, 1 of every 10 children between ages 5 and 17 work to help the family survive (Figure 6.8).

Figure 6.8

This young boy spends much of his day carrying bricks.

Zatletic/ Dreamstime.com

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6.2dFactors That Affect Death Rates

The rapid growth of the world’s population over the past 100 years is largely the result of declining death rates, especially in less-developed countries. More people in some of these countries live longer, and fewer infants die because of larger food supplies, improvements in food distribution, better nutrition, improved sanitation, safer water supplies, and medical advances such as immunizations and antibiotics.

A useful indicator of the overall health of people in a country or region is  life expectancy : the average number of years a person born in a particular year can be expected to live. Between 1955 and 2018, average global life expectancy increased from 48 years to 72 years. Between 1900 and 2018, the average U.S. life expectancy rose from 47 years to 79 years. Research indicates that poverty, which reduces the average life span by 7 to 10 years, is the single most important factor affecting life expectancy. For example, the average life expectancy in the world’s 10 poorest nations is 55 years compared to 80 years in the 10 wealthiest nations.

Another important indicator of the overall health of a population is its  infant mortality rate , the number of babies out of every 1,000 born who die before their first birthday. It is viewed as one of the best measures of a society’s quality of life because it indicates the general level of nutrition and health care. A high infant mortality rate usually indicates insufficient food (undernutrition), poor nutrition (malnutrition; see Figure 1.14), and a high incidence of infectious disease. Infant mortality also affects the TFR. In areas with low infant mortality rates, women tend to have fewer children because fewer of their children die at an early age.

Infant mortality rates in most countries have declined dramatically since 1965 (Figure 6.9). Even so, every year more than 4 million infants die of preventable causes during their first year of life, according to UN population experts. Most of these deaths occur in less-developed countries. This average of nearly 11,000 mostly unnecessary infant deaths per day is equivalent to 55 jet airliners, each loaded with 200 infants, crashing every day with no survivors.

Figure 6.9

Comparison of infant mortality rates in more-developed countries and less-developed countries, 1950–2018, with projections to 2050 based on medium population projections.

(Compiled by the authors using data from United Nations Population Division and Population Reference Bureau.)

Between 1900 and 2018, the U.S. infant mortality rate dropped from 165 to 5.6. This sharp decline was a major factor in the marked increase in U.S. average life expectancy during this period. However, 53 other nations had lower infant mortality rates than the United States in 2018.

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6.2eMigration

A third factor in population change is  migration : the movement of people into (immigration) and out of (emigration) specific geographic areas. Most people who migrate to another area within their country or to another country are seeking jobs and economic improvement. Others are driven by religious persecution, ethnic conflicts, political oppression, or war. There are also environmental refugees—people who have to leave their homes and sometimes their countries because of water or food shortages, soil erosion, or some other form of environmental degradation.

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6.3aAge Structure

The age structure of a population is the numbers or percentages of males and females in young, middle, and older age groups in that population. Age structure is an important factor in determining total fertility rates and whether the population of a country increases or decreases.

Population experts construct a population age-structure diagram by plotting the percentages or numbers of males and females in the total population in each of three age categories: pre-reproductive (ages 0–14), consisting of individuals normally too young to have children; reproductive (ages 15–44), those normally able to have children; and post-reproductive (ages 45 and older), with individuals normally too old to have children. Figure 6.10 presents generalized age-structure diagrams for countries with rapid, slow, zero, and negative (declining) population growth rates.

Figure 6.10

Generalized population age-structure diagrams for countries with rapid (1.5–3%), slow (0.3–1.4%), zero (0–0.2%), and negative (declining) population growth rates.

Question:

1. Which of these diagrams best represents the country where you live?

(Compiled by the authors using data from U.S. Census Bureau and Population Reference Bureau.)

A country with a large percentage of people younger than age 15 (represented by a wide base in Figure 6.10, far left) will experience rapid population growth unless death rates rise sharply. Because of this demographic momentum, the number of births in such a country will rise for several decades. This will occur even if women each have an average of only one or two children because of the large number of girls entering their prime reproductive years. Most future human population growth will take place in less-developed countries because of their typically youthful age structure and rapid population growth rates.

300%

Projected increase in the global population of people over 65 between 2016 and 2050

The global population of seniors—people who are 65 and older—is projected to triple between 2018 and 2050 when one of every six people will be a senior. (See the Case Study that follows.) An aging population combined with a lower fertility rate results in fewer working-age adults having to support a large number of seniors. For example, in China and the United States between 2010 and 2050, the working-age population is projected to decline sharply. This could lead to a shortage of workers and friction between the younger and older generations in these countries.

Case Study

The American Baby Boom

Changes in the distribution of a country’s age groups have long-lasting economic and social impacts. For example, the American baby boom (Figure 6.5) added 79 million people to the U.S. population between 1946 and 1964. Over time, this group looks like a bulge as it moves up through the country’s age structure, as shown in Figure 6.11.

Figure 6.11

Age-structure diagrams tracking the baby-boom generation in the United States, 1955, 1985, 2015, and 2035 (projected).

Critical Thinking:

1. How might the projected age structure in 2035 affect you?

(Compiled by the authors using data from U.S. Census Bureau and Population Reference Bureau.)

For decades, the baby-boom generation has strongly influenced the U.S. economy because it makes up about 25% of the U.S. population. Baby boomers created the youth market in their teens and twenties and are now creating the late middle age (ages 50 to 60) and senior markets. In addition to having this economic impact, the large baby-boom generation plays an important role in deciding who is elected to public office and what laws are passed or weakened.

Since 2011, when the first baby boomers began turning 65, the number of Americans older than age 65 has grown at the rate of about 10,000 a day and will do so through 2030. This process has been called the graying of America. As the number of working adults declines in proportion to the number of seniors, there may be political pressure from baby boomers to increase tax revenues to help support the growing senior population. However, in 2015, the Millennial Generation—Americans born between 1980 and 2005—overtook Baby Boomers to become the largest generation living in the United States. This could lead to economic and political conflicts between older and younger Americans.

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6.3bAging Populations Can Decline Rapidly

The graying of the world’s population is due largely to declining birth rates and medical advances that have extended life spans. The UN estimates that by 2050, the global number of people age 60 and older will equal or exceed the number of people under age 15 (Figure 6.12).

Figure 6.12

The world’s age structure 1950, 2010, and 2050 (projected).

Critical Thinking:

1. How might the projected age structure in 2050 affect you?

(Compiled by the authors using data from U.S. Census Bureau and United Nations Population Division.)

As the percentage of people age 65 or older increases, more countries will begin experiencing population declines. If population decline is gradual, its harmful effects usually can be managed. However, some countries, such as Japan, are experiencing rapid declines and feeling such effects more severely.

Japan has the world’s highest percentage of people age 65 or over and the world’s lowest percentage of people under age 15. In 2018, Japan’s TFR was 1.4 births per woman, one of the lowest in the world. In 2018, Japan’s population was 127 million. By 2050, its population is projected to be 102 million. As its population declines, there will be fewer adults working and paying taxes to support an increasingly elderly population. Because Japan discourages immigration, this could threaten its economic future. In recent years, Japan has been feeling the effects of a declining population. For example, houses in some suburbs have been abandoned and cannot be sold because of a lack of buyers. They could be demolished, but who will pay the costs—the owners who have abandoned them, or the government?

Figure 6.13 lists some of the problems associated with rapid population decline. Population declines are difficult to reverse

Figure 6.13

Rapid population decline can cause several problems.

Critical Thinking:

1. Which two of these problems do you think are the most important?

Top: Slavoljub Pantelic/ Shutterstock.com. Center: Iofoto/ Shutterstock.com. Bottom:sunabesyou/ Shutterstock.com.

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6.4aEconomic Development

Some analysts argue that we need to slow population growth in order to reduce degradation of our life-support system. They have suggested several ways to do this, one of which is to reduce poverty through economic development.

Demographers have examined the birth and death rates of western European countries that became industrialized during the 19th century. Using such data, they developed a hypothesis on population change known as the  demographic transition . It states that as countries become industrialized and economically developed, their per capita incomes rise, poverty declines, and their populations tend to grow more slowly. According to the hypothesis, this transition takes place in four stages, as shown in Figure 6.14. Some good news for those who view population growth as a serious environmental problem is that by 2018, 38 countries, mostly in Europe, had stabilized their populations or were experiencing population declines.

Figure 6.14

The demographic transition, which a country can experience as it becomes industrialized and more economically developed, can take place in four stages.

Question:

1. At what stage is the country where you live?

Some analysts believe that most of the world’s less-developed countries will make a demographic transition over the next few decades. They hypothesize that the transition will occur because newer technologies will help them to develop economically and to reduce poverty.

Other analysts fear that rapid population growth, extreme poverty, war, increasing environmental degradation, and resource depletion could leave some countries with high population growth rates stuck in stage 2 of the demographic transition. This highlights the need to reduce poverty as a key to improving human health and stabilizing population.

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6.4bEducating and Empowering Women

A number of studies show that women tend to have fewer children if they are educated, can control their own fertility, earn an income of their own, and live in societies that do not suppress their rights. In most societies, women have fewer rights and fewer educational and economic opportunities than men have.

Women do almost all of the world’s domestic work and childcare for little or no pay. They provide more unpaid health care (within their families) than do all of the world’s organized health-care services combined. In rural areas of Africa, Latin America, and Asia, women do 60–80% of the work associated with growing food, hauling water, and gathering and hauling wood (Figure 6.15) and animal dung for use as fuel. As one Brazilian woman observed, “For poor women, the only holiday is when you are asleep.”

Figure 6.15

This woman in Nepal is bringing home firewood. Typically, she spends 2 hours a day, two or three times a week, on this task.

Iv Nikolny/ Shutterstock.com

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6.4cFamily Planning

Family planning  programs provide education and clinical services that can help couples to choose how many children to have and when to have them. Such programs vary from culture to culture, but most of them provide information on birth spacing, birth control, and health care for pregnant women and infants.

According to studies by the UN Population Division and other population agencies, family planning has been a major factor in reducing the number of unintended pregnancies, births, and abortions. In addition, family planning has reduced rates of infant mortality, the number of mothers and fetuses dying during pregnancy, and population growth rates. According to the UN, had there not been the sharp drop in TFRs since the 1970s, with all else being equal, the world’s population today would be about 8.5 billion instead of 7.6 billion (Core Case Study). Family planning has played an important role in countries that have stabilized their populations.

Family planning also has financial benefits. Studies show that each dollar spent on family planning in countries such as Thailand, Egypt, and Bangladesh saves $10 to $16 in health, education, and social service costs by preventing unwanted births.

Despite these successes, certain problems have hindered progress in some countries. There are three major problems. First, according to the UN Population Fund and the Guttmacher Institute, about 40% of all pregnancies in less-developed countries were unplanned and about half of these pregnancies end with abortion. So, ensuring access to voluntary contraception would play a key role in stabilizing the populations and reducing the number of abortions in such countries.

Second, according to the UN Population Fund, an estimated 214 million women, primarily in the world’s poorest countries, are not using safe and effective family planning methods. Meeting these current unmet needs for family planning and contraception could prevent more than 80 million unintended pregnancies, 36 million induced abortions (millions of them unsafe), 1 million infant deaths, and 76,000 pregnancy-related deaths of women per year. It would also provide economic benefits. For every dollar invested in contraception, the cost of pregnancy-related care is reduced by $2.20.

The experiences of countries such as Japan, Thailand, Bangladesh, South Korea, Taiwan, and China show that a country can achieve or come close to replacement-level fertility within a decade or two. The real population story of the past 50 years has been the sharp reduction in the rate of population growth (Figure 6.2) resulting from the reduction of poverty through economic development, empowerment of women, and the promotion of family planning. However, the global population is still growing fast enough to add up to 3 billion more people by 2050.

Case Study

Figure 6.16 shows changes in India’s age structure between 2010 and 2035 (projected). The UN projects that by 2029, India will be the world’s most populous country, and that by 2050, it will have a projected population of 1.7 billion.

Figure 6.16

Age structure changes in India: 2010 and 2035 (projected).

Critical Thinking:

1. How might the projected age structure in 2035 affect India’s ability to reduce poverty?

(Compiled by the authors using data from U.S. Census Bureau and United Nations Population Division.)

India has the world’s fourth largest economy and a rapidly growing middle class. However, the country faces serious poverty, malnutrition, and environmental problems that could worsen as its population continues to grow rapidly. India is home to one-third of the world’s poorest people. About one-fourth of all people in India’s cities live in slums, and prosperity and progress have not touched hundreds of millions of Indians who live in rural villages. According to the World Bank, about 30% of India’s population—one-third of the world’s extremely poor people—live in extreme poverty on less than $1.25 per day (Figure 6.17). For decades, the Indian government has provided family planning services throughout the country and has strongly promoted a smaller average family size. Even so, Indian women have an average of 2.3 children.

Figure 6.17

Homeless people in Kolkata, India.

Samrat35/ Dreamstime.com

India’s rapid economic growth is expected to accelerate over the next few decades. This will help many people in India escape poverty, but it will also increase pressure on India’s and the earth’s natural capital as per capita resource use increases. India already faces serious soil erosion, overgrazing, water pollution, and air pollution problems. On the other hand, economic growth may help India to slow its population growth by accelerating its demographic transition (Figure 6.14).

Case Study

Slowing Population Growth in China

China is the world’s most populous country, with 1.39 billion people in 2018. According to the Population Reference Bureau and the United Nations Population Fund, China’s population is projected to peak at 1.4 billion in 2030 and then to decline to 1.3 billion by 2050.

In the 1960s, China’s large population was growing so rapidly that there was a serious threat of mass starvation. To avoid this, government officials took measures that eventually led to the establishment of the world’s most extensive, intrusive, and strict family planning and birth control program.

The goal of the program, established in 1978, has been to sharply reduce population growth by promoting one-child families. The government provided contraceptives, sterilizations, and abortions for married couples. Married couples pledging to have no more than one child received better housing, more food, free health care, salary bonuses, and preferential job opportunities for their child. Couples who broke their pledge lost such benefits.

Since this government-controlled program began in 1978, China has made impressive efforts to feed its people and bring its population growth under control. Between 1972 and 2018, the country reduced its TFR from 3.0 to 1.8—one of the fastest demographic transitions (Figure 6.14) in history. China’s population is now growing more slowly than the U.S. population. Although China has avoided mass starvation, its strict population control program has been accused of violating human rights.

An unintended result of China’s population control program is that because of the cultural preference for sons, many Chinese women have aborted female fetuses. This has reduced the female population and it is estimated that by 2020, there will be 30 million more Chinese men than women looking for a partner.

Since 1980, China has undergone rapid industrialization and economic growth. According to the Earth Policy Institute, between 1990 and 2010 this process reduced the number of people living in extreme poverty by almost 500 million. It has also helped more than 400 million Chinese—a number greater than the entire U.S. population—to become middle-class consumers. However, millions of people live in poverty in China’s villages and cities (Figure 6.18). China’s rapidly growing middle class will consume more total resources. This will put a strain on China’s and the earth’s natural capital. Like India, China faces serious soil erosion, overgrazing, water pollution, and air pollution problems.

Figure 6.18

Old and new housing in heavily populated Shanghai, China, in 2015.

Nikada/iStock/Getty Images Plus/Getty Images

Because of its one-child policy, in recent years the average age of China’s population has been increasing at one of the fastest rates ever recorded. In 2018, at least 123 million Chinese people were over age 65—the largest number of people in this age group of all the world’s countries. Figure 6.19 shows China’s age structure in 2010 and its projected age structure in 2035. Since 2017, China’s birth rate has declined, dropping by 12% in 2018. The UN estimates that by 2030, the country is likely to have too few young workers (ages 15 to 64) to support its rapidly aging population. This graying of the Chinese population could lead to a declining work force, limited funds for supporting continued economic development, and fewer children and grandchildren to care for the growing number of elderly people. These concerns and other factors may slow China’s economic growth. To help deal with this problem, China plans to become the world’s largest manufacturer of industrial robots to be used for manufacturing. It will also sell such robots to other countries.

Figure 6.19

Age structure in China: 2010 and 2035 (projected).

Critical Thinking:

1. How might the projected age structure in 2035 affect China’s economy?

(Compiled by the authors using data from U.S. Census Bureau and United Nations Population Division.)

Because of these concerns, in 2015, the Chinese government abandoned its one-child policy and replaced it with a two-child policy. Married couples can apply to the government for permission to have two children. However, because of the high cost of raising a second child, and because young women enjoy greatly increased educational and job opportunities, many married couples still choose to have only one child.

Big Ideas

· The human population is growing rapidly and may soon bump up against environmental limits.

· The combination of population growth and the increasing rate of resource use per person is expanding the overall human ecological footprint and putting a strain on the earth’s natural capital.

· We can slow human population growth by reducing poverty, elevating the status of women, and encouraging family planning.

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Tying It All TogetherWorld Population Growth and Sustainability

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This chapter began with a discussion of the fact that the world’s human population has now reached 7.6 billion (Core Case Study). We noted that this is a result of exponential population growth and that many environmental scientists believe such growth to be unsustainable in the end. We briefly considered some of the environmental problems brought on by exponential human population growth. We looked at factors that influence the growth of populations, as well as at how some countries have made progress in controlling population growth.

In the first six chapters of this book, you have learned how ecosystems and species have been sustained throughout the earth’s history, in keeping with the three scientific principles of sustainability, by nature’s reliance on solar energy, nutrient cycling, and biodiversity (see inside back cover of this book). These three principles can guide us in dealing with the problems brought on by population growth and decline. By greatly increasing our use of solar, wind, and other renewable-energy technologies, we can cut pollution and emissions of climate-changing gases that are increasing as the population and resource use per person grow. By reusing and recycling more materials, we can cut resource waste and reduce our ecological footprints. By focusing on preserving biodiversity, we can help sustain the life-support system on which we and all other species and our economies depend.

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Chapter Review

1. Do you think that the global population of 7.6 billion (Core Case Study) is too large? Explain. If your answer was yes, what do you think should be done to slow human population growth? If your answer was no, do you believe that there is a population size that would be too big? Explain.

2. If you could say hello to a new person every second without taking a break and working around the clock, how many people could you greet in a day? How many in a year? How long would it take you to greet the 91 million people who were added to the world’s population in 2018? At this same rate, how many years would it take you to greet all 7.7 billion people living on the earth in 2018?

3. Of the three major environmental worldviews summarized in chapter 1, which do you think underlies each of the two major positions on whether the world is overpopulated, as described in Science Focus 6.1? Explain.

4. Should everyone have the right to have as many children as they want? Explain. Is your belief on this issue consistent with your environmental worldview?

5. Is it rational for a poor couple in a less-developed country such as India to have four or five children? Why or why not?

6. Do you think that projected increases in the earth’s population size and economic growth are sustainable? Explain. If not, how is this likely to affect your life?

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Chapter Review

Doing Environmental Science

1. Prepare an age-structure diagram for your community. You will need to estimate how many people belong in each age category (see Figure 6.11). To do this, interview a randomly drawn sample of the population to find out their ages and then divide your sample into age groups. (Be sure to interview equal numbers of males and females.) Then find out the total population of your community and apply the percentages for each age group from your sample to the whole population in order to make your estimates. Create your diagram and then use it to project future population trends. Write a report in which you discuss some economic, social, and environmental effects that might result from these trends.

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Chapter Review

Data Analysis

The chart below shows selected population data for two different countries, A and B. Study the chart and answer the questions that follow.

1. Calculate the rates of natural increase (due to births and deaths, not counting immigration) for the populations of country A and country B. Based on these calculations and the data in the table, for each of the countries, suggest whether it is a more-developed country or a less-developed country and explain the reasons for your answers.

2. Describe where each of the two countries might be in the stages of demographic transition (Figure 6.14). Discuss factors that could hinder either country from progressing to later stages in the demographic transition.

3. Explain how the percentages of people under age 15 in each country could affect its per capita and total ecological footprints.

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