1. The Human Population and Its Impact6
The Human Population and Its Impact

2. 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?

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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 Question: The U.S. fertility rate has declined and remained at or below replacement levels since So why is the population of the United States still increasing?
Fig. 6-5, p. 127

15. 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?

16. 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 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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 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

29. Case Study: The American Baby Boom
79 million people added from
36% of adults
Affect politics and economics
Now becoming senior citizens
Graying of America

30. 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

31. Populations Made Up of Mostly Older People Can Decline Rapidly
Slow decline
Manageable
Rapid decline
Economic problems
Proportionally fewer young people working
Labor shortages

32. 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

33. 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

34. The AIDS Tragedy (cont’d.)
Figure 6-15: In Botswana, more than 25% of people ages 15–49 were infected with HIV in 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

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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?

42. 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

43. Case Study: Slowing Population Growth in India (cont’d.)
Figure 6-20: Homeless people in Kolkata, India in 2011.
Fig. 6-20, p. 137

44. 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

45. 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

46. 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

47. 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