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The Human Population and Its Impact

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1 The Human Population and Its Impact
Chapter 6

2 Key Concepts How many people can the earth support? What factors influence the size of the human population? How does a population’s age structures affect its growth or decline? How can we slow human population growth?

3 Core Case Study: Are There Too Many of Us?
Estimated 2.4 billion more people by 2050 Are there too many people already? Will technological advances overcome environmental resistance that populations face? Should populations be controlled? Will growing populations cause increased environmental stresses?

4 6-1 How Many People Can the Earth Support?
1) 3 major factors account for the population increase a) ability to expand into new habitats b) Agriculture allows us to feed more people c) Sanitation, antibiotics and vaccines 2) Death rates dropped causing the increase in population 3) Current rate of growth is 1.22% per year a) Developed 0.1% b) Developing 1.5%

5 4) How many people by 2050 5) Cultural carrying capacity: optimum level that would allow most people to live in reasonable comfort and freedom without effecting the future generation

6 Science Focus: How Long Can the Human Population Keep Growing?
Thomas Malthus and population growth: 1798 Humans have altered 83% of the earth’s land surface Can the human population grow indefinitely?

7 6-2 What Factors Influence the Size of the Human Population?
1) Population change: same as last chapter 2) Crude rates: number of births or deaths per 1000 people in a population

8 3) Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population
a) Fertility rate: number of children born to a woman in her lifetime b) Replacement level fertility rate: ave. number of children that couple must have to replace themselves c) Current replacement rate: 2.1 in developed and 2.5 in some developing d) At 2.1 rate, the population would continue to grow for 50 years

9 e) Total fertility rate (TFR): ave
e) Total fertility rate (TFR): ave. number of children born to women during their reproductive years f) Global average 2.6 in 2008 (1.6 developed & 2.8 developing)

10 Case Study: The U.S. Population Is Growing Rapidly
Drop in TFR in U.S. Rate of population growth has slowed Population still growing and not leveling off Fourfold increase since 1900 Changes in lifestyle in the U.S. during the 20th century

11 4) Several Factors Affect Birth & Fertility Rates
a) Importance of children in labor force b) Cost of raising & educating a child (290K in US) c) Availability of pension systems d) Urbanization e) Educational & employment opportunities for women f) Infant mortality rate (# of live births who die before age 1) g) Average age at marriage h) Availability of legal abortions i) Availability of birth control j) Religious beliefs, traditions and cultural norms

12 5) Several Factors Affect Death Rates
a) Largest reason for increased population is a decrease in death rates b) Better food supplies & distribution c) Better nutrition and medical advances d) Improved sanitation e) Safer water f) Indicators of health: 1. Life expectance (ave. # of yrs an infant may live) 2. Infant mortality rate

13 Several Factors Affect Death Rates (2)
g) Why the U.S. infant mortality rate is high Inadequate health care for poor women during pregnancy and their infants Drug addiction among pregnant women High birth rate among teenagers h) Infant mortality rate indicates food supply, nutrition & infectious diseases i) 4 million infants die of preventable causes per year

14 6) Migration Affects an Area’s Population Size
Economic improvement Religious freedom Political freedom Wars Environmental refugees

15 Case Study: The United States: A Nation of Immigrants
Historical role of immigration in the U.S. Legal immigration Illegal immigration

16 6-3 How Does a Population’s Age Structure Affect Its Growth or Decline?
1) Age structure diagrams a) distribution of males & females by age group b) Large pre-reproductive will probably grow c) Nearly 28% of people were under 15 in 2008

17 Figure 6.13: Global outlook: These charts illustrate 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? (Data from United Nations Population Division and Population Reference Bureau)

18 2) Age-Structures can be used to Make Population and Economic Projections
a) Baby boomers added 70 million b) B.B. make up almost half of the adults c) They dominate demand for goods & services d) Important roles in elections and laws e) Will cause the over 65 to increase starting in 2011 f) Their retirement will cause a shortage of workers

19 3) Populations Made Up of Mostly Older People Can Decline Rapidly
a) Slow decline is manageable b) Rapid decline can cause severe economic & social problems c) Strains budgets: medical care, social security, other services, with fewer paying in d) Labor shortages

20 4) Populations Can Decline from a Rising Death Rate: The AIDS Tragedy
a) 25 million killed by 2008 b) Many young adults die: loss of most productive workers c) Sharp drop in life expectancy d) Loss of the young workers e) International community called upon to 1. Reduce the spread of HIV through education and health care 2. Financial assistance and volunteers

21 Figure 6.16: Global outlook: Worldwide, AIDS is the leading cause of death for people ages 15–49. This loss of productive working adults can affect the age structure of a population. In Botswana, more than 24% of this age group was infected with HIV in 2008 and about 148,000 people died. 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). See the Data Analysis Exercise at the end of this chapter for further analysis of this problem. (Data from the U.S. Census Bureau) Question: How might this affect Botswana’s economic development? Fig. 6-16, p. 139

22 6-4 How Can We Slow Human Population Growth?
1) Demographic Transition: Hypothesis of population change tracking death rate decrease & birth rate increase through 4 stages

23 As Countries Develop, Their Populations Tend to Grow More Slowly
2) Demographic trap: countries getting stuck in stage 2 due to various factors (page 133) 3) Family planning works a) has been a major factor in reducing the number of births b) has decreased the number of abortions c) had decreased the number of mother & fetus deaths d) Remaining problems: 42% of pregnancies are unplanned & 201 million couples want to limit the number of children, but lack access in developing countries

24 4) Empowering Women Slows Population Growth
a) Women tend to have fewer children if they are educated, hold paying jobs outside the home and live in societies where their rights are not suppressed. b) If daughters are not valued, they are not always educated c) Teaching women to read decrease population poor women who cannot read have 5-7 children compared to 2 or less where most women can.

25 Case Study: Slowing Population Growth in China: the One-Child Policy
Encourages fewer children Gender imbalance Fast-growing economy Face serious resource and environmental problems

26 Case Study: Slowing Population Growth in India
Population control: gender bias Poverty Malnutrition Environmental problems

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