3 Managing Our Population and Consumption Crowded mall.

sculpies/iStock /Getty Images Plus Learning Outcomes

After reading this chapter, you should be able to

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

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. Preagricultural Period

The preagricultural period of human history dated from over 100,000 years ago to about 10,000 years ago. During this time, humans developed primitive cultures, tools, and skills and slowly migrated out of Africa to settle Europe, Asia, Australia, and the Americas. Disease, conflict, food insecurity, and environmental conditions kept human numbers low, perhaps as low as 50,000 to 100,000 across the entire planet. That’s about the same as today’s population of a small

city in the United States, such as Albany, New York; Trenton, New Jersey; Roanoke, Virginia; or Tuscaloosa, Alabama. By the end of the preagricultural period about 10,000 years ago, the human population across the globe had risen to roughly 5 million to 10 million, about the same as New York City today. Agricultural Period

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

The introduction of automatic machinery around the middle of the 18th century ushered in the industrial period, the period we are still in today. A combination of factors has caused dramatic increases in the human population during this time. The Industrial Revolution led to sharp increases in food production. Advances in science resulted in improved medicines and medical care. Better understanding of communicable diseases prompted improvements in sanitation and water quality. All of these developments helped extend life expectancy, reduce 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. J-curve line graph showing human population growth from 5 million in 8000 BCE to 7.7 billion in 2019. Brackets show that the agricultural period started in 8000 BCE and the industrial period around 1850.

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

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

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

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

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

of the village at the end of the year to be 1,012. Migration Woman waits at a counter to check on her immigration status.

Karen Kasmauski /SuperStock

When calculating population change, immigration and emigration must also be considered.

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. Fertility

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

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

The link between fertility rates, the age structure of a population, and overall birth rates has led demographers to develop a visual tool they call an age-structure pyramid. 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

Country

CBR (per 1,000)

CDR (per 1,000)

TFR

Net migration rate (per 1,000)

Rate of natural increase (percentage)

World

19

7

2.4

N/A

1.2

Uganda

41

9

5.4

–1

3.2

United States

12

9

1.8

3

0.3

Japan

8

11

1.4

1

–0.3

Source: “2018 World Population Data Sheet,” by Population Reference Bureau, 2018 (https://www.prb.org/wp-content/uploads/ 2018/08/2018_WPDS.pdf). 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. Three population pyramids; the y-axis lists age groups, the left x- axis is the male population in millions, and the right x-axis is the female population in millions. Uganda’s pyramid is wider at the bottom; the U.S. pyramid is more evenly distributed; and Japan’s pyramid is wider at the top.

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

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

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

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

On the complete opposite end of the spectrum from Uganda is Japan. Japan’s age-structure pyramid actually gets wider at the middle and upper portions, suggesting that fertility rates are well below

replacement levels and that overall population is stable or declining. Table 3.1 confirms this. The TFR in Japan is currently 1.4, and the CBR of 8 is lower than the CDR of 11. Overall, Japan’s population is currently declining at a rate of –0.3% annually, with moderate levels of positive net migration helping slow the rate of population decline. Learn More: Visualizing Population Growth

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

https://www.npr.org/templates/event/embeddedVideo.php? storyId=141816460&mediaId=141848264 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. Line graph showing population increasing, death rate decreasing, and birth rate decreasing before all stabilizing as a country moves through the demographic transition. Contributing Factors

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

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

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

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

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

The United States and other developed countries were well into Phase 2 or 3 of the demographic transition by the start of the 20th century. Today these countries are in Phase 4, with very low fertility rates, low birth rates, and low death rates. In contrast, many developing countries were still in Phase 1 or 2 of the demographic transition as late as 1950. These countries had not seen the advances in medicine, food supply, clean water, and sanitation that the developed countries

had achieved. In addition, many developing countries were still largely rural and dependent on agriculture, a situation that tends to promote high fertility and large family size. As a result, developing countries were characterized by high birth and death rates. From roughly 1950 onward, however, developing countries began to enter Phases 2 and 3 of the demographic transition, and their populations increased rapidly as a result. Today some developing countries, especially in Asia, are approaching or have already reached Phase 4 of the demographic transition. Meanwhile, others—especially in sub- Saharan Africa—could still be categorized as being in Phase 2 or 3.

Table 3.2 provides comparative demographic data for the world as a whole and for seven countries in different stages of the demographic transition. The West African country of Mali can still be said to be in Phase 2 of the demographic transition. Fertility and birth rates are still high, but improved access to medicine, sanitation, and food has dropped death rates to almost the world average. As a result, Mali’s population is growing at a rapid rate of 3.5% and will double every 20 years if the growth rate remains the same. Senegal, also in West Africa, and Egypt in North Africa are moving from Phase 2 to Phase 3 of the demographic transition as fertility rates and birth rates have begun to decline in recent years. India is now solidly in Phase 3 of the demographic transition, since fertility rates have dropped to 2.3 and birth rates to 20 per 1,000. However, because India has a relatively young population—the age-structure pyramid is wider at the bottom—there is some built-in demographic momentum. As a result, India, already the second most populous country in the world after China, will become the most populous around the year 2022. The Southeast Asian nation of Malaysia is further along in the demographic transition than India. Meanwhile, countries like Denmark and South Korea are clearly already in Phase 4, a situation characterized by low fertility, low birth and death rates, and stable or even declining populations. Table 3.2: Demographic data for countries in different phases

Country

CBR

CDR

TFR

Rate of natural increase

Demographic transition phase

World

19

7

2.4

1.2

3/4

Mali

45

10

6.0

3.5

2

Senegal

33

6

4.6

2.7

2/3

Egypt

27

6

3.4

2.1

2/3

India

20

6

2.3

1.4

3

Malaysia

16

5

1.9

1.1

3/4

Denmark

11

9

1.8

0.2

4

South Korea

7

6

1.1

0.1

4

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

Because virtually all developed countries are in Phase 4 of the demographic transition, and because most developing countries are still in Phases 2 or 3, demographers predict with confidence that virtually all the world’s population growth in the decades ahead will be in developing countries (see Figure 3.4). Close to 60% of that global increase in population will take place in Africa, with smaller

increases in Asia and the Americas. Europe’s population is projected to decline by about 16 million—not surprising, given the low fertility rates in most European countries. These are all projections, however. How much population growth will actually occur, and how fast we reach 8, 9, or 10 billion, will depend on how quickly developing countries move through the demographic transition. The speed of a country’s demographic transition will ultimately depend on the decisions made by young people in those countries. Section 3.4 will cover the role of population policy in affecting those decisions and “speeding up” the demographic transition. 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. Line graph showing the population of less developed countries growing from roughly 6.5 billion today to almost 10 billion in 2100, while the population of more developed countries remains around 1 billion.

Data from “World Population Prospects: The 2017 Revision,” DVD edition, by United Nations, Department of Economic and Social Affairs, Population Division, 2017 (https://population.un.org/wpp/Download/ Standard/Population). 3.4 Population Policy and Fertility Control

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

However, slight changes in fertility rates can have a profound impact on demographic trends. An increase in average fertility of just 0.5 children per woman could lead to a global population of over 15 billion by 2100. Likewise, a decrease in average fertility of 0.5 would result in a global population of 6.2 billion by 2100, over 1 billion less than today. Any

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