The Human Population and Its Impact 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?

Industrial revolution Core Case Study: Planet Earth: Population 7 Billion 2011 (7 billion) Billions of people 1999 (6 billion) 1987 (5 billion) 1974 (4 billion) 1960 (3 billion) Figure 6.1 The human population has grown exponentially—showing slow growth throughout most of history and shooting up at a rapid rate within the last 200 years. This graph also shows projections to 2100 that range from 8 billion to 16 billion. (This figure is not to scale.) 1930 (2 billion) 1800 (1 billion) Time Hunting and gathering 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

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

Annual Growth Rate of World Population, 1950-2010 Figure 6-2: The annual growth rate of world population has generally dropped since the 1960s, but the population has continued to grow (Figure 6-1). Fig. 6-2, p. 123

Where Population Growth Occurred, 1950-2010 World population (in billions) Figure 6-3: Most of the world’s population growth between 1950 and 2012 took place in the world’s less-developed countries. This gap has been projected to increase between 2012 and 2050. 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

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 Figure 6-4: We humans 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 our growing population (Concept 6-1). Questions: In your daily living, do you think you contribute directly or indirectly to any of these harmful environmental impacts? Which ones? Explain. 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

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

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

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

Total Fertility Rates Total Fertility Rate Births per woman Baby boom (1946–64) Replacement level Figure 6-5: The graph shows the total fertility rates for the United States between 1917 and 2012. Question: 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? 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?

Married women working outside the home 8% 81% 77 years Life expectancy 47 years 1900 2000 Married women working outside the home 8% 81% High school graduates 15% 83% Homes with flush toilets 10% 98% Homes with electricity 2% 99% Living in suburbs 10% 52% Figure 6-7 Some major changes took place in the United States between 1900 and 2000. Question: Which two of these changes do you think had the biggest impacts on the U.S. ecological footprint? Hourly manufacturing job wage (adjusted for inflation) $3 $15 Homicides per 100,000 people 1.2 5.8 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

Legal Immigration to the United States 1907 1914 New laws restrict immigration Number of legal immigrants (thousands) Great Depression Figure 6.6 Legal immigration to the United States, 1820–2006 (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 before January 1, 1982. 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

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

Several Factors Affect Birth Rates and Fertility Rates (cont’d.) Figure 6-9: This young girl is breaking granite into gravel in the Kerala State of India. 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

Several Factors Affect Death Rates (cont’d.) Less-developed countries (deaths per 1,000 live births) Infant mortality rate World Figure 6-10: Infant mortality rates for the world’s more-developed countries and less-developed countries, 1950–2012, with projections to 2050 based on medium population projections. More-developed countries Year Fig. 6-10, p. 129

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

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

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

A Population’s Age Structure Helps Us Make Projections (cont’d.) Male Female Male Female Male Female Male Female Animated Figure 6-11 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: Which of these diagrams best represents the country where you live? Expanding Rapidly Guatemala Nigeria Saudi Arabia Expanding Slowly United States Australia China Stable Japan Italy Greece Declining Germany Bulgaria Russia Prereproductive ages 0–14 Reproductive ages 15–44 Postreproductive ages 45–85+ Fig. 6-11, p. 131

A Population’s Age Structure Helps Us Make Projections (cont’d.) Figure 6-12: Population structure by age and sex in less-developed countries and more-developed countries for 2011. Question: If all girls under 15 were to have only one child during their lifetimes, how do you think these structures would change over time? 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

Case Study: The American Baby Boom (cont’d.) Animated Figure 6-13 Age-structure charts tracking the baby-boom generation in the United States, 1955, 1985, 2015 (projected), and 2035 (projected). 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

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 Figure 6-14: Rapid population decline can cause several problems. Question: Which two of these problems do you think are the most important? 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

The AIDS Tragedy (cont’d.) Figure 6-15: In Botswana, more than 25% of people ages 15–49 were infected with HIV in 2011. This figure shows two projected age structures for Botswana’s population in 2020—one including the possible effects of the AIDS epidemic (red bars), and the other not including those effects (yellow bars). Question: How might this affect Botswana’s economic development? 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

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

Birth rate and death rate Population grows very slowly because of a high birth rate (to compensate for high infant mortality) and a high death rate Stage 1 Preindustrial Growth rate over time 80 70 60 50 40 30 20 10 (number per 1,000 per year) Birth rate and death rate Low Death rate Total population Birth rate Population grows rapidly because birth rates are high and death rates drop because of improved food production and health Decreasing Stage 2 Transitional Increasing Very high Population growth slows as both birth and death rates drop because of improved food production, health, and education Stage 3 Industrial Low Population growth levels off and then declines as birth rates equal and then fall below death rates Stage 4 Postindustrial Negative Zero Animated Figure 6-16 The demographic transition, which a country can experience as it becomes industrialized and more economically developed, can take place in four stages. Question: At what stage is the country where you live? 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

Empowering Women Can Slow Population Growth (cont’d.) Figure 6-17: This woman in Nepal is bringing home firewood. Typically, she spends 2 hours a day, 2 or 3 times a week, on this task. 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

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?

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

Case Study: Slowing Population Growth in India (cont’d.) Figure 6-20: Homeless people in Kolkata, India in 2011. 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

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

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

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