LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER • SCOTT E. SPOOLMAN

6

The Human Population and Its Impact

Core Case Study: Planet Earth: Population 7 Billion • The evolution of Homo sapiens and a total population of 2 billion has taken 200,000 years • It has taken less than 50 years to reach the second 2 billion • It took 25 years to add the third 2 billion • Twelve years later, the population topped 7.1 billion • What is a sustainable human population?

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Core Case Study: Planet Earth: Population 7 Billion

Hunting and gathering

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2011 (7 billion) 1999 (6 billion) 1987 (5 billion) 1974 (4 billion) 1960 (3 billion) 1930 (2 billion) 1800 (1 billion) Time Agricultural revolution Industrial revolution Fig. 6-1, p. 122

6-1 How Do Environmental Scientists Think about Human Population Growth?

• The continuing rapid growth of the human population and its impacts on natural capital raise questions about how long the human population can keep growing © Cengage Learning 2015

Human Population Growth Shows Certain Trends • Rate of population growth has slowed in recent decades • Human population growth is unevenly distributed geographically • People are moving from rural to urban areas © Cengage Learning 2015

Annual Growth Rate of World Population, 1950-2010

Fig. 6-2, p. 123

Where Population Growth Occurred, 1950 2010

Population in less-developed countries Population in more-developed countries Year Fig. 6-3, p. 123

Human Population Growth Impacts Natural Capital • As the human population grows, so does the global total human ecological footprint • Cultural carrying capacity – Total number of people who could live in reasonable freedom and comfort indefinitely, without decreasing the ability of the earth to sustain future generations © Cengage Learning 2015

Natural Capital Degradation Altering Nature to Meet Our Needs Reducing biodiversity Increasing use of net primary productivity Increasing genetic resistance in pest species and disease causing bacteria Eliminating many natural predators Introducing harmful species into natural communities Using some renewable resources faster than they can be replenished Disrupting natural chemical cycling and energy flow Relying mostly on polluting and climate-changing fossil fuels Fig. 6-4, p. 125

6-2 What Factors Influence the Size of the Human Population? • Population size increases through births and immigration, and decreases through deaths and emigration • The average number of children born to women in a population (total fertility rate) is the key factor that determines population size © Cengage Learning 2015

The Human Population Can Grow, Decline, or Remain Fairly Stable • Population change = (births + immigration) – (deaths + emigration) • Crude birth rate – The number of live births/1000/year • Crude death rate – The number of deaths/1000/year © Cengage Learning 2015

Women Are Having Fewer Babies, But the World’s Population Is Still Growing • Fertility rate – Number of children born to a woman during her lifetime • Replacement-level fertility rate – Average number of children a couple must have to replace themselves – Approximately 2.1 in developed countries – Up to 2.5 in developing countries © Cengage Learning 2015

The World’s Population Is Still Growing (cont’d.) • Total fertility rate (TFR) – Average number of children born to women in a population – Between 1955 and 2012, the global TFR dropped from 5 to 2.4

– However, to eventually halt population growth, the global TFR will have to drop to 2.1

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Total Fertility Rate Total Fertility Rates

Baby boom (1946 –64) Replacement level Fig. 6-5, p. 127

Case Study: The U.S. Population – Third Largest and Growing • Population still growing and not leveling off – 76 million in 1900 – 314 million by 2012 • Drop in TFR in U.S.

– Rate of population growth has slowed • What have been some changes in lifestyle in the U.S. during the 20th century?

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Life expectancy Married women working outside the home 8% High school graduates 15% Homes with flush toilets Homes with electricity 2% 10% 10% Living in suburbs Hourly manufacturing job wage (adjusted for inflation) $3 Homicides per 100,000 people 1.2

47 years 77 years 81% 83% 52% $15 5.8

98% 99% 1900 2000 Stepped Art Fig. 6-7, p. 132

Case Study: The U.S. Population – Third Largest and Growing (cont’d.) • Immigration – U.S. has admitted almost twice as many immigrants and refugees as all other countries combined © Cengage Learning 2015

© Cengage Learning 2015 Legal Immigration to the United States

1907 1914 New laws restrict immigration Great Depression Year Fig. 6-6, p. 127

Several Factors Affect Birth Rates and Fertility Rates • Children as part of the labor force • Cost of raising and educating children • Availability of private and public pension • Urbanization • Educational and employment opportunities for women © Cengage Learning 2015

Several Factors Affect Birth Rates and Fertility Rates (cont’d.) • Average age of a woman at marriage • Availability of legal abortions • Availability of reliable birth control methods • Religious beliefs, traditions, and cultural norms © Cengage Learning 2015

Several Factors Affect Birth Rates and Fertility Rates (cont’d.)

Fig. 6-9, p. 129

Several Factors Affect Death Rates • Life expectancy • Infant mortality rate – Number of live births that die in first year • High infant mortality rate indicates: – Insufficient food – Poor nutrition – High incidence of infectious disease © Cengage Learning 2015

Several Factors Affect Death Rates (cont’d.)

Less-developed countries World More-developed countries Year Fig. 6-10, p. 129

Migration Affects an Area’s Population Size • Migration – The movement of people into and out of specific geographic areas • Causes: – Economic improvement – Religious and political freedom – Wars • Environmental refugees © Cengage Learning 2015

6 3 How Does a Population’s Age Structure Affect Its Growth or Decline? • The numbers of males and females in young, middle, and older age groups determine how fast a population grows or declines © Cengage Learning 2015

A Population’s Age Structure Helps Us Make Projections • Age structure categories – Prereproductive ages (0-14) – Reproductive ages (15-44) – Postreproductive ages (45 and older) • Seniors are the fastest-growing age group © Cengage Learning 2015

A Population’s Age Structure Helps Us Make Projections (cont’d.)

Male Female Male Female Male Female Male Female Expanding Rapidly Guatemala Nigeria Saudi Arabia Prereproductive ages 0 –14 Expanding Slowly United States Australia China Reproductive ages 15 –44 Stable Japan Italy Greece Declining Germany Bulgaria Russia Postreproductive ages 45 –85+ Fig. 6-11, p. 131

A Population’s Age Structure Helps Us Make Projections (cont’d.) © Cengage Learning 2015

Fig. 6-12, p. 132

Case Study: The American Baby Boom • 79 million people added from 1946-1964 – 36% of adults • Affect politics and economics • Now becoming senior citizens – Graying of America © Cengage Learning 2015

Case Study: The American Baby Boom (cont’d.)

Fig. 6-13, p. 132

Populations Made Up of Mostly Older People Can Decline Rapidly • Slow decline – Manageable • Rapid decline – Economic problems • Proportionally fewer young people working • Labor shortages © Cengage Learning 2015

Some Problems with Rapid Population Decline Can threaten economic growth Labor shortages Less government revenues with fewer workers Less entrepreneurship and new business formation Less likelihood for new technology development Increasing public deficits to fund higher pension and health-care costs Pensions may be cut and retirement age increased Fig. 6-14, p. 133

Populations Can Decline due to a Rising Death Rate: The AIDS Tragedy • AIDS has killed more than 30 million people • Many young adults die – loss of most productive workers • Sharp drop in life expectancy • International community – Reduce the spread of HIV through education and health care – Financial assistance and volunteers © Cengage Learning 2015

The AIDS Tragedy (cont’d.)

Fig. 6-15, p. 134

6-4 How Can We Slow Human Population Growth? • We can slow human population growth by reducing poverty, elevating the status of women, and encouraging family planning © Cengage Learning 2015

The First Step Is to Promote Economic Development • Demographic transition – As countries become industrialized • First death rates decline • Then birth rates decline • Four stages – Preindustrial – Transitional – Industrial – Postindustrial © Cengage Learning 2015

40 30 20 10 0 Stage 1 Preindustrial 80 70 Population grows very slowly because of a high birth rate (to compensate for high infant mortality) and a high death rate 60 50 Low Stage 2 Transitional Population grows rapidly because birth rates are high and death rates drop because of improved food production and health Birth rate Increasing Total population Very high Death rate Decreasing Growth rate over time Stage 3 Industrial Stage 4 Postindustrial Population growth slows as both birth and death rates drop because of improved food production, health, and education Population growth levels off and then declines as birth rates equal and then fall below death rates Low Zero Negative Stepped Art Fig. 6-16, p. 135

Empowering Women Can Slow Population Growth • Factors that decrease total fertility rates: – Education – Paying jobs – Ability to control fertility • Women: – Do most of the domestic work and child care – Provide unpaid health care – 2/3 of all work for 10% of world’s income – Discriminated against legally and culturally © Cengage Learning 2015

Empowering Women Can Slow Population Growth (cont’d.)

Fig. 6-17, p. 135

Family Planning Can Provide Several Benefits • Family planning in less-developed countries – Responsible for a 55% drop in TFRs – Financial benefits – money spent on family planning saves far more in health, education costs © Cengage Learning 2015

Family Planning Can Provide Several Benefits (cont’d.) • Two problems – 42% pregnancies unplanned, 26% end with abortion – Many couples do not have access to family planning • How can family planning programs be expanded?

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Case Study: Slowing Population Growth in India • Population: 1.26 billion people in 2012 • Problems – Poverty, malnutrition, and environmental degradation • Causes – Bias toward having male children – Poor couples want many children – Only 47% of couples use family planning © Cengage Learning 2015

Case Study: Slowing Population Growth in India (cont’d.)

Fig. 6-20, p. 137

Case Study: Slowing Population Growth in China: A Success Story • World’s most populous country • Threat of mass starvation in the 1960s • Government established a strict family planning and birth control program – Reduced number of children born per woman from 5.7 to 1.5

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Three Big Ideas • The human population is increasing rapidly and may soon bump up against environmental limits • Increasing use of resources per person – Expanding the overall human ecological footprint and putting a strain on the earth’s resources © Cengage Learning 2015

Three Big Ideas (cont’d.) • We can slow population growth by reducing poverty through economic development, elevating the status of women, and encouraging family planning © Cengage Learning 2015

Tying It All Together: World Population Growth and Sustainability • Exponential growth is unsustainable in the long run • Employing solar and other renewable technologies can help cut: – Pollution – Emissions of climate-changing gases • Reuse and recycle materials • Focus on preserving biodiversity © Cengage Learning 2015