Chapter 8 Cont`d.

Lecture Outlines
Chapter 8
The Science behind the
4th Edition
© 2011 Pearson Education, Inc.
This lecture will help you understand:
• Human population growth
• Different viewpoints on this
• Population, affluence, and
technology’s effects
• Demography
• Demographic transition
• Factors affecting population
• The HIV/AIDS epidemic
• Population and sustainable development
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Case study: China’s one-child policy
• In 1970, China’s 790 million
people faced starvation
• The government instituted a
one-child policy
- The growth rate plummeted
- The policy is now less strict
• The successful program has
unintended consequences:
- Killing of female infants
- Black-market trade in
teenage girls
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Our world at seven billion
• Populations continue to rise in most countries
- Particularly in poverty-stricken developing nations
• Although the rate of growth is slowing, we are still
increasing in numbers
It would take 30 years,
counting once each second,
to count to a billion!
It would take 210 years to
count to 7 billion!
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The human population is growing rapidly
• Our population grows by over 80 million each year
• It took until 1800 to reach 1 billion
• In 1930 (130 years later) we reached 2 billion
• We added the most recent billion in 12 years
Due to exponential growth,
even if the growth rate
remains steady, population
will continue to grow
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Rates of growth vary from region to region
• At today’s 1.2% global growth rate, the population
will double in 58 years (70/1.2 = 58)
• If China’s rate had continued at 2.8%, it would
have had 2 billion people in 2004
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Is population growth a problem?
• Technology, sanitation, medication, and increased food
increase population
- Death rates drop, but not birth rates
• Population growth was seen as good
- Support for elderly, a larger labor
• Thomas Malthus’ An Essay on the
Principles of Population (1798)
- Humans will outstrip food supplies
- War, disease, starvation reduce
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Paul Ehrlich’s Population Bomb (1968)
• Neo-Malthusians: population
growth will increase faster than
food production
• Population growth causes famine
and conflict
- Civilization would end by the
end of the 20th century
• Intensified food production fed
more people
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Population growth will affect quality of life
• Population growth has caused famine, disease, conflict
• Prosperity, education, gender equality reduce birth rates
• Cornucopians (e.g., economists) say new resources will
replace depleted ones
- But some resources (e.g., species) are irreplaceable
• Quality of life will suffer with unchecked growth
- Less space, food, wealth per person
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Some governments fear falling populations
• Policymakers believe population growth increases
economic, political, and military strength
• But growth is correlated with poverty, not wealth
- Strong, rich nations have low growth rates
- Weak, poor nations have high growth rates
• Some nations offer incentives for more children
- Elderly need social services
• 49% of non-European nations feel their birth rates are
too high
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Population growth affects the environment
• The IPAT model: I = P × A × T × S
• Total impact (I) on the environment results from:
- Population (P) = individuals need space and resources
- Affluence (A) = greater per capita resource use
- Technology (T) = increased exploitation of resources
- Sensitivity (S) = how sensitive an area is to human
• Further model refinements include the effects of
education, laws, and ethics on the formula
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Population growth with limited resources
• Impact equates to pollution or resource consumption
- Humans use 25% of Earth’s net primary production
• Technology has increased efficiency and reduced our
strain on resources
- Resulting in further population growth
- For example: increased agricultural production
• Modern China’s increasing affluence is causing:
- Increased resource consumption
- Farmland erosion, depleted aquifers, urban pollution
• China shows us what the rest of the world can become
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Population growth: causes and consequences
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Human population growth and regulation
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Human population growth and regulation
© 2011 Pearson Education, Inc.
• Demography: the application of population ecology
to the study of change in human populations
- All population principles apply to humans
- Environmental factors limit population growth
• Humans raise the environment’s carrying capacity
through technology
• How many humans can the world sustain?
- 1–33 billion: prosperity to abject poverty
- Population growth can’t continue forever
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• Demographers study:
- Population size
- Density and
- Age structure
- Sex ratio
- Birth, death, immigration, and
emigration rates
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Population size and density
• The UN predicts 9 billion by
• Increased density impacts
the environment
- But relieves pressure in
less-populated areas
• Highest density: temperate,
subtropical, tropical biomes
- Cities
• Lowest density: away from
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Population distribution
• Humans are unevenly distributed around the globe
• Unpopulated areas tend to be environmentally sensitive
(high S value in the IPAT equation)
- Vulnerable to humans (e.g., deserts, arid grasslands)
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Age structure affects population size
• Age structure diagrams (population pyramids) show age
• Wide base = many young:
- High reproduction
- Rapid population growth
• Even age distribution:
- Remains stable
- Births = deaths
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Age structures: Canada vs. Madagascar
Canada’s age structure is
Madagascar’s age structure
is heavily weighted toward
the young
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Changing age structures pose challenges
• China’s age structure is changing
- In 1970, the median age was 20
- By 2050, it will be 45
• By 2050, over 300 million will be over 65
- Fewer people will be
working to support
social programs
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Many populations are aging
• Many populations are getting older
- They will need care and financial assistance
- Taxes will increase for Social Security and Medicare
• But fewer dependent
children means lower
crime rates
• The elderly can
remain productive
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Sex ratios
• Human sex ratios at birth slightly favor males
- For every 100 females born, 106 males are born
• Chinese females are selectively aborted
- 120 boys were reported for 100 girls
- Cultural gender preferences
- The government’s one-child policy
• The undesirable social consequences?
- Many single Chinese men
- Teenage girls are kidnapped and sold as brides
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Factors in population change
• Whether a population grows, shrinks, or remains
stable depends on rates of birth, death, and
- Birth and immigration add individuals
- Death and emigration remove individuals
• Technological advances caused decreased deaths
- The increased gap between birth and death rates
resulted in population expansion
• Natural rate of population change = due to birth
and death rates alone
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Immigration and emigration
• War, civil strife, and environmental degradation cause
people to flee their homes
- Each year, 25 million refugees escape poor
environmental conditions
• This movement causes environmental problems
- No incentives to conserve resources
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Falling growth rates do not mean fewer
Slower rates of growth do not mean a decreasing
population—population size continues to increase
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Factors affecting total fertility rate
• Total fertility rate (TFR) = the average number
of children born to each female
• Replacement fertility = the TFR that keeps the
size of a population stable (about 2.1)
• Causes of decreasing TFR:
- Medical care reduces infant mortality
- Urbanization increases childcare costs
- Children go to school instead of working
- Social Security supports the elderly
- Educated women enter the labor force
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Life expectancy is increasing
• In countries with good sanitation, health care, and
food, people live longer
• Life expectancy = average number of years that
an individual is likely to continue to live
- Increases with reduced rates of infant mortality
• Urbanization, industrialization, and personal
wealth reduce infant mortality rates
• Demographic transition = a model of economic
and cultural change
- Explains the declining death and birth rates in
industrializing nations
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The demographic transition
• A stable pre-industrial state of high birth and death rates
changes to a stable post-industrial state of low birth and
death rates
• As mortality decreases, there is less need for large
- Parents invest in quality of life
• Death rates fall before birth rates
- Resulting in population growth
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Human population growth and regulation
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The demographic transition’s four stages
Population growth is seen as a temporary phenomenon
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Is the demographic transition universal?
• It has occurred in Europe, the U.S., Canada, Japan, and
other nations over the past 200–300 years
• But it may or may not apply to developing nations
• The transition could fail in cultures that:
- Place greater value on childbirth or
- Grant women fewer freedoms
For people to attain the material standard of living of
North Americans, we would need the natural
resources of four and a half more Earths
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Birth control: key to controlling growth
• The greatest single factor slowing population growth
• Birth control = controlling the number of children born
- Reducing the frequency of pregnancy
• Contraception = deliberate prevention of pregnancy
through a variety of methods
• Family planning = affects the number and spacing of
- Clinics offer advice, information, and contraceptives
- Hindered by religious and cultural influences
- Rates range from 10% (Africa) to 90% (China)
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Contraceptive methods for birth control
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Empowering women reduces growth rates
• Fertility rates drop when women gain access to
contraceptives, family planning programs, and
educational opportunities
• Women with little power have unintended pregnancies
- Two-thirds of the world’s illiterate are women
Educating women reduces
fertility rates, delays
childbirth, and gives them a
voice in reproductive
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Human population growth and regulation
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Human population growth and regulation
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We are a long way from gender equity
• Over 60% of the world’s poor are women
• Violence against women remains shockingly common
- Many men resist women’s decision making
• The gap is obvious at high levels of government
- We are a long way from achieving gender equality
The U.S. lags behind the
world in proportion of
women representatives
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Policies and family planning work
• Many countries provide incentives, education,
contraception, and reproductive health care
• Funding and policies that encourage family planning
lower population growth rates in all nations
• Thailand’s educational-based approach to family
planning reduced its growth rate from 2.3% to 0.6%
- Brazil, Mexico, Iran, Cuba, and other developing
countries have active programs
• 1994’s UN population conference in Cairo, Egypt called
for universal access to reproductive health care
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Family planning reduces fertility rates
Blue = with
family planning
Red = without
family planning
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Poverty and population growth are correlated
• Poorer societies have
higher population growth
- Consistent with the
demographic transition
- They have higher
fertility and growth
rates, with lower
contraceptive use
99% of the next billion people added will be born in poor,
less developed regions that are least able to support them
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Correlation of poverty and population
• Poverty exacerbates population growth
- Population growth exacerbates poverty
• In 1960, 70% of all people lived in developing nations
- As of 2010, 82% live in these nations
- 99% of the next billion will be born in these nations
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Poverty causes environmental degradation
• Population growth in poor nations increases
environmental degradation
- Farming degrades soil in arid areas (Africa, China)
- Poor people cut forests, deplete biodiversity, and hunt
endangered species (e.g., great apes)
Africa’s Sahel and western
China are turning to desert
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Wealth also impacts the environment
• The population problem is not only in poor countries
• Affluent societies have enormous resource consumption
and waste production
- People use resources from other areas, as well as
from their own
- Ecological footprints are huge
• We are living beyond our means
One American has as much environmental impact
as 4.5 Chinese or 10 Indians or 19 Afghans
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The Earth can’t support our consumption
• Biocapacity = the amount of biologically productive land
and sea available to us
- Ecological deficit = ecological footprint > biocapacity
- Ecological reserve = ecological footprint < biocapacity
• We are running a global ecological deficit
Humanity’s global
ecological footprint
surpassed Earth’s
capacity in 1987
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The wealth gap and population growth cause
• The contrast between rich and poor societies causes
social and environmental stress
- The richest 20% use 86% of the world’s resources
- Increasing tensions between “haves” and “have-nots”
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HIV/AIDS impacts African populations
• The AIDS epidemic is having the greatest impact
since the Black Death in the 14th century
• Of 33 million infected, two-thirds live in subSaharan Africa; 3,800 die/day
• Low rates of contraceptive use spread the disease
HIV is established
and spreading quickly
around the world
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AIDS has severe effects
• AIDS undermines the ability of poor nations to develop
- Millions of orphans are created
- Fewer teachers and workers to fill jobs
- Families and communities break down
- Income and food production decline
- Debt and medical costs skyrocket
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Demographic fatigue
• Demographic fatigue = governments face
overwhelming challenges related to population growth
- With the added of stress of HIV/AIDS, governments
are stretched beyond their capabilities
- Problems grow worse and citizens lose faith
• Good news: HIV transmission has slowed recently
Decreased AIDS deaths are
due to policy, collaboration,
research, NGOs, and
grassroots efforts
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Sustainable development and population
• Millennium Development Goals = UN’s 2000
- Specific targets can be met with concrete strategies
- Global partnerships with corporations, governments,
• Population control is not a goal
- But to achieve the goals, population growth and
resource consumption must be addressed
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Millennium Development Goals
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• The human population is larger than at any other time
• Rates are decreasing but populations are still rising
• Most developed nations have passed through the
demographic transition
• Expanding women’s rights slows population growth
• How will the population stop rising?
- The demographic transition, governmental
intervention, or disease and social conflict?
• Sustainability requires a stabilized population to avoid
destroying natural systems
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What has accounted for most of the world’s population
growth in recent years?
a) Women are having more babies.
b) Technology, medicine, and food have decreased death
c) Fewer women are using contraceptives.
d) Nothing, the population has dropped in recent years.
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According to the I = P x A x T x S formula, what would
happen to the impact if China’s 1 billion people had a
lifestyle like Americans?
a) Their population would automatically drop.
b) Their population would automatically increase.
c) Their affluence and technology would increase.
d) Their impact on the environment would decrease.
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Where is the highest density of people found?
a) In the colder climates (e.g., Siberia)
b) In temperate or tropical biomes
c) In rural areas
d) In drier areas
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An age structure diagram shaped like a pyramid, with a
wide base shows an ________ population.
a) Increasing
b) Decreasing
c) Stable
d) Older
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Describe the relationship between population growth
rates and population size.
a) Falling growth rates automatically mean a smaller
b) Falling growth rates automatically mean a larger
c) Falling growth rates means we no longer have a
population problem.
d) Falling growth rates does not mean a smaller
population, but that rates of increase are slowing.
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QUESTION: Weighing the Issues
Should the United States fund international familyplanning efforts?
a) Yes, absolutely
b) Yes, but only in nations that follow U.S.-approved
c) Only if it can influence the nations’ policies
d) Never under any circumstances, it’s not our job
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QUESTION: Weighing the Issues
Would you rather live in a country with a larger population
or smaller population?
a) Small population, so there will be more resources for
b) Small population, so there will be more resources for
others, including wildlife
c) Large population, so I can find a date
d) Large population, because people are our biggest
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QUESTION: Interpreting Graphs and Data
What happens
during the
“transitional” stage
of the demographic
a) High birth and death rates rise - population increases
b) High birth and death rates - population is stable
c) High birth rates with low death rates - population
d) Low birth and death rates cause - population decreases
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QUESTION: Interpreting Graphs and Data
According to this age pyramid, Madagascar’s future
population will be:
a) Balanced
b) Larger
c) Much larger
d) Smaller
e) Much smaller
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QUESTION: Interpreting Graphs and Data
According to these graphs, which countries had access
to family planning?
a) Iraq and Pakistan
b) Malawi and Haiti
c) Malawi and Kenya
d) Kenya and
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