1. THE HUMAN POPULATION & ITS IMPACT
CHAPTER 6

2. How many people can earth support?
For most of history, the human population grew very slowly
However, the last 200 years have seen rapid, exponential growth in this population

4. Three factors account for this population increase:
Humans have developed the ability to settle in almost all of the earth’s climate zones & habitats
The emergence of early and modern agriculture have allowed us to consistently increase that amount of food we can grow per unit of land
Death rates have dropped sharply because of improved sanitation and health care
So, most of the increase in population for the last 100 years is a sharp drop in death rates-not a sharp rise in birth rates

5. The annual growth rate of world population has generally dropped since the 1960s, but the population has continued to grow
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).

6. 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

7. 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

8. 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

9. What factors influence the size of the human population?
Population size increases through births and immigration, and decreases through deaths and emigration
Population Change = (Births + Immigration) –
(Deaths + Emigration)
Crude birth rate : number of live births per 1,000 people in a population per year
Crude death rate: number of deaths per 1,000 people in a population per year

10. 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

11. 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

12. 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
Average age of a woman at marriage
Availability of legal abortions
Availability of reliable birth control methods
Religious beliefs, traditions, and cultural norms

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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
Two problems
42% pregnancies unplanned, 26% end with abortion
Many couples do not have access to family planning