The Human Population and Its Impact - TVHS...

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LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER • SCOTT E. SPOOLMAN

6 The Human Population and Its

Impact

• The evolution of Homo sapiens and a total

population of 2 billion has taken 200,000

• 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?

Core Case Study: Planet Earth: Population

7 Billion

Fig. 6-1, p. 122

Hunting and

gathering

Agricultural revolution Industrial

revolution

Billio

1800 (1 billion)

2011 (7 billion) 1999 (6 billion) 1987 (5 billion)

1974 (4 billion)

1960 (3 billion)

1930 (2 billion)

Core Case Study: Planet Earth: Population 7 Billion

• 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

6-1 How Do Environmental Scientists

Think about Human Population Growth?

• Rate of population growth has slowed in

recent decades

• Human population growth is unevenly

distributed geographically

• People are moving from rural to urban

Human Population Growth Shows Certain

Trends

Annual Growth Rate of World Population,

1950-2010

Fig. 6-2, p. 123

Where Population Growth Occurred, 1950-

Fig. 6-3, p. 123

Population in less-developed countries

Population in more-developed countries

• 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

Human Population Growth Impacts Natural

Capital

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

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

• 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

6-2 What Factors Influence the Size of the

Human Population?

• 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

The Human Population Can Grow,

Decline, or Remain Fairly Stable

• 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

Women Are Having Fewer Babies, But the

World’s Population Is Still Growing

• 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

The World’s Population Is Still Growing

(cont’d.)

Total Fertility Rate Total Fertility Rates

Baby boom

(1946–64)

Replacement

Fig. 6-5, p. 127

• 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?

Case Study: The U.S. Population – Third

Largest and Growing

77 years Life expectancy 47 years

Married women working

outside the home 8%

High school

graduates

Homes with flush

toilets

Homes with

electricity 2%

Living in

suburbs

Hourly manufacturing job

wage (adjusted for inflation) $3

Homicides per

100,000 people

5.8 Stepped Art

Fig. 6-7, p. 132

• Immigration

– U.S. has admitted almost twice as many

immigrants and refugees as all other

countries combined

Case Study: The U.S. Population – Third

Largest and Growing (cont’d.)

Fig. 6-6, p. 127

New laws

restrict

immigration

Depression

Legal Immigration to the United States

• 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

• Average age of a woman at marriage

• Availability of legal abortions

• Availability of reliable birth control methods

• Religious beliefs, traditions, and cultural

Fertility Rates (cont’d.)

Fig. 6-9, p. 129

• 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

Several Factors Affect Death Rates (cont’d.)

Fig. 6-10, p. 129

Less-developed

countries

(death

More-developed

countries

• Migration

– The movement of people into and out of

specific geographic areas

• Causes:

– Economic improvement

– Religious and political freedom

– Wars

• Environmental refugees

Migration Affects an Area’s Population Size

• The numbers of males and females in

young, middle, and older age groups

determine how fast a population grows or

declines

6-3 How Does a Population’s Age

Structure Affect Its Growth or Decline?

• 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

Make Projections (cont’d.)

Fig. 6-11, p. 131

Male Female Male Female Male Female Male Female

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+

Make Projections (cont’d.)

Fig. 6-12, p. 132

• 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.)

Fig. 6-13, p. 132

• Slow decline

– Manageable

• Rapid decline

– Economic problems

• Proportionally fewer young people working

• Labor shortages

Populations Made Up of Mostly Older

People Can Decline Rapidly

Fig. 6-14, p. 133

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

Increasing public deficits to fund higher

pension and health-care costs

Pensions may be cut and retirement age

increased

• 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

Populations Can Decline due to a Rising

Death Rate: The AIDS Tragedy

The AIDS Tragedy (cont’d.)

Fig. 6-15, p. 134

• We can slow human population growth by

reducing poverty, elevating the status of

women, and encouraging family planning

6-4 How Can We Slow Human Population

Growth?

• Demographic transition

– As countries become industrialized

• First death rates decline

• Then birth rates decline

• Four stages

– Preindustrial

– Transitional

– Industrial

– Postindustrial

The First Step Is to Promote Economic

Development

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

Stepped Art

Population growth

levels off and then

declines as birth

rates equal and

then fall below

death rates

Stage 4

Postindustrial

Negative Zero

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

Population growth

slows as both birth

and death rates

drop because of

improved food

production, health,

and education

Stage 3

Industrial

Fig. 6-16, p. 135

• 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

Empowering Women Can Slow Population

Growth (cont’d.)

Fig. 6-17, p. 135

• 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

Family Planning Can Provide Several

Benefits

• 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?

Family Planning Can Provide Several

Benefits (cont’d.)

• 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

Case Study: Slowing Population

Growth in India (cont’d.)

Fig. 6-20, p. 137

• 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

Case Study: Slowing Population Growth in

China: A Success Story

The Human Population and Its Impact - TVHS...

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