The Human Population and Its Impact

Chapter 6

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?

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?

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%

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

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?

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

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

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)

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

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

5) Several Factors Affect Death Rates

a) Largest reason for increased population is a decrease in death rates

b) Better food supplies & distributionc) Better nutrition and medical advancesd) Improved sanitatione) Safer waterf) Indicators of health:

1. Life expectance (ave. # of yrs an infant may live)2. Infant mortality rate

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

6) Migration Affects an Area’s Population Size

Economic improvement

Religious freedom

Political freedom

Wars

Environmental refugees

Case Study: The United States: A Nation of Immigrants

Historical role of immigration in the U.S.

Legal immigration

Illegal immigration

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

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

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

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

Fig. 6-16, p. 139

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

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

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.

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

Case Study: Slowing Population Growth in India

Population control: gender bias

Poverty

Malnutrition

Environmental problems