LIVING IN THE ENVIRONMENT, 18e
G. TYLER MILLER • SCOTT E. SPOOLMAN
6
The Human Population and Its
Impact
©©Cengage
CengageLearning
Learning2015
2015
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?
© Cengage Learning 2015
Core Case Study: Planet Earth: Population 7 Billion
Billions of people
2011 (7 billion)
1999 (6 billion)
1987 (5 billion)
1974 (4 billion)
1960 (3 billion)
1930 (2 billion)
1800 (1 billion)
Time
Hunting and
gathering
Agricultural revolution
Industrial
revolution
© Cengage Learning 2015
Fig. 6-1, p. 122
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
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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
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Annual Growth Rate of World Population,
1950-2010
Fig. 6-2, p. 123
World population (in billions)
Where Population Growth Occurred, 19502010
Population in less-developed countries
Population in more-developed countries
Year
Fig. 6-3, p. 123
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
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Natural Capital Degradation
Altering Nature to Meet Our Needs
Reducing biodiversity
Increasing use of net primary
productivity
Increasing genetic resistance in
pest species and diseasecausing 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
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
© Cengage Learning 2015
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
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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
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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
© Cengage Learning 2015
Total Fertility Rate
Births per woman
Total Fertility Rates
Baby boom
(1946–64)
Replacement
level
Fig. 6-5, p. 127
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?
© Cengage Learning 2015
47 years
Life expectancy
77 years
Married women working
outside the home
8%
81%
15%
High school
graduates
83%
10%
Homes with flush
toilets
Homes with
electricity
Living in
suburbs
Hourly manufacturing job
wage (adjusted for inflation)
Homicides per
100,000 people
98%
2%
99%
10%
52%
$3
1900
2000
$15
1.2
5.8
Stepped Art
Fig. 6-7, p. 132
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
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Number of legal immigrants (thousands)
Legal Immigration to
the United States
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1907
1914
New laws
restrict
immigration
Great
Depression
Year
Fig. 6-6, p. 127
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
© Cengage Learning 2015
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
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Several Factors Affect Birth Rates and
Fertility Rates (cont’d.)
Fig. 6-9, p. 129
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
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Infant mortality rate
(deaths per 1,000 live births)
Several Factors Affect Death Rates (cont’d.)
Less-developed
countries
World
More-developed
countries
Year
Fig. 6-10, p. 129
Migration Affects an Area’s Population Size
• Migration
– The movement of people into and out of
specific geographic areas
• Causes:
– Economic improvement
– Religious and political freedom
– Wars
• Environmental refugees
© Cengage Learning 2015
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
© Cengage Learning 2015
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
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A Population’s Age Structure Helps Us
Make Projections (cont’d.)
Male
Female
Male
Female
Expanding Rapidly
Guatemala Nigeria
Saudi Arabia
Expanding Slowly
United States
Australia China
Prereproductive ages
0–14
Reproductive ages
15–44
Male
Female Male
Stable Japan
Italy Greece
Female
Declining Germany
Bulgaria Russia
Postreproductive ages 45–85+
Fig. 6-11, p. 131
A Population’s Age Structure Helps Us
Make Projections (cont’d.)
© Cengage Learning 2015
Fig. 6-12, p. 132
Case Study: The American Baby Boom
• 79 million people added from 1946-1964
– 36% of adults
• Affect politics and economics
• Now becoming senior citizens
– Graying of America
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Case Study: The American Baby Boom
(cont’d.)
Fig. 6-13, p. 132
Populations Made Up of Mostly Older
People Can Decline Rapidly
• Slow decline
– Manageable
• Rapid decline
– Economic problems
• Proportionally fewer young people working
• Labor shortages
© Cengage Learning 2015
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
Fig. 6-14, p. 133
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
© Cengage Learning 2015
The AIDS Tragedy (cont’d.)
Fig. 6-15, p. 134
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
© Cengage Learning 2015
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
© Cengage Learning 2015
Birth rate and death rate
(number per 1,000 per year)
Stage 1
Preindustrial
Stage 2
Transitional
Population
grows very
slowly because
of a high
birth rate
(to compensate
for high infant
80 mortality) and a
70 high death rate
Population grows rapidly
because birth rates are high and
death rates drop because of
improved food production and
health
Stage 3
Industrial
Stage 4
Postindustrial
Population growth
slows as both birth
and death rates
drop because of
improved food
production, health,
and education
Population growth
levels off and then
declines as birth
rates equal and
then fall below
death rates
Total population
60
Birth rate
50
40
30
Death rate
20
10
0
Low
Increasing
Very high
Decreasing
Growth rate over time
Low
Zero
Negative
Stepped Art
Fig. 6-16, p. 135
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
© Cengage Learning 2015
Empowering Women Can Slow Population
Growth (cont’d.)
Fig. 6-17, p. 135
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
© Cengage Learning 2015
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?
© Cengage Learning 2015
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
© Cengage Learning 2015
Case Study: Slowing Population
Growth in India (cont’d.)
Fig. 6-20, p. 137
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
© Cengage Learning 2015
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
© Cengage Learning 2015
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
© Cengage Learning 2015
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
© Cengage Learning 2015