Transcript Document

The Human Population and Its Impact
Chapter 6
World Population
http://www.census.gov/popclock/
World Population Distribution
World Population Density
World Land Area
World Population Density
The size of each territory shows the relative proportion of
the world's population living there.
World Population Growth Rates
World Population Growth
Pop. Size...
Reached in...
Interval between next
1 Billion people...
1 Billion
1804
2 Billion
1927
123 years later
3 billion
1960
33 years later
4 Billion
1974
14 years later
5 Billion
1987
13 years later
6 Billion
1999
12 years later
7 Billion
2011
12 years later
8 Billion
2028
17 years later
9 billion
2050
22 years later
Core Case Study:
Are There Too Many of Us?
 The world’s population is projected to increase from
7 billion to 9.3 billion between 2012 and 2050.
 Much of the world’s population growth occurs in
rapidly developing countries like China and India.
Core Case Study:
Are There Too Many of Us?
 Some argue that the planet has too many people.
 Some feel that the world can support billions of
more people due to technological advances.
 There is a constant debate over the need to reduce
population growth.
• Must consider moral, religious, and personal freedom.
 The debate over interactions among population
growth, economic growth, politics, and the impact
on the environment is one of the most important
and controversial issues in environmental science.
6-1 How Many People Can the Earth Support?
 Concept 6-1 We do not know how long we can
continue increasing the earth’s carrying capacity for
humans without seriously degrading the life-support
system for humans and many other species.
Human Population Growth Continues
but It Is Unevenly Distributed
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Reasons for human population increase:
1. Movement into new habitats and climate zones
2. Early and modern agriculture methods
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Feed more people per unit of land
3. Control of infectious diseases through
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Sanitation systems
Antibiotics
Vaccines
http://www.pbs.org/wgbh/nova/earth/global-population-growth.html
Human Population Growth Continues
but It Is Unevenly Distributed
 We do not know how long we can continue increasing the
earth’s carrying capacity.
• There will likely be between 7.2 - 10.6 billion people on earth by 2050.
• 97% of growth is in developing countries with many people living in
acute poverty.
 What is the optimum sustainable population of the earth
based on the cultural carrying capacity?
• Maximum pop. our planet could support in a sustainable manner
that would also allow most people to live in reasonable comfort.
Human Population Growth Continues
but It Is Unevenly Distributed
 U.N. world population projection based on women having an
average of 2.5 (high), 2.0 (medium), or 1.5 (low) children.
 In 2006, the population of developed countries grew at 0.1% per year.
 Developing countries grew 15 times faster at 1.5% per year.
Science Focus: How Long Can the
Human Population Keep Growing?
 Thomas Robert Malthus (1798)
 He predicted that the human population would grow
exponentially while food production would increase linearly
 Human population growth would outstrip the Earth's
carrying capacity and that disease and famines would limit
humanity's growth.
 Although humans have altered 83% of the earth’s land
surface, his predictions have not yet come true.
 Technology has allowed food production
to increase exponentially as well…
...for now.
6-2 What Factors Influence the Size
of the Human Population?
 Concept 6-2A Population size increases
because of births and immigration and
decreases through deaths and emigration.
 Concept 6-2B The average number of children
born to women in a population (total fertility rate)
is the key factor that determines population size.
Populations Can Grow, Shrink,
or Remain Stable
 Populations increase through:
• Births
• Immigration = arrival of individuals from outside the population
 Populations decrease through:
• Deaths
• Emigration = departure of individuals from the population
The Human Population Can Grow, Decline,
or Remain Fairly Stable
 Instead of using raw numbers, crude birth rates and
crude death rates are used .
• Based on total number of births or deaths per 1,000
people in a population
• It makes it possible to compare birth/death rates for
countries with greatly different total populations.
• It’s also much easier to find population growth rates using
the crude birth/death rates than using the raw numbers
Global Connections:
Crude birth/death rates
Population comparison
Women Having Fewer Babies but Not Few
Enough to Stabilize the World’s Population
 The average number of children that a woman
bears has dropped sharply.
 However, this decline is not enough to stabilize the
world’s population in the near future.
• Replacement-level fertility: the number of children a
couple must bear to replace themselves.
• 2.1 in developed, 2.54 in developing
• Why difference between developed/developing?
• Total fertility rate (TFR): the average number of
children a woman has during her reproductive years.
• 2.7 worldwide (1.6 in developed, 2.9 in developing)
Case Study:
The U.S. Population Is Growing Rapidly
 U.S. pop. grew by nearly 2.9 million people in 2008:
• 66% occurred because of births outnumbering deaths.
• ~34% came from illegal and legal immigration.
In 2008, the TFR in
the United States
was 2.1 per woman
Case Study:
The U.S. Population Is Growing Rapidly
 The population of the U.S. has grown from 76 million in 1900
to 310 in 2010 despite oscillations in TFR and birth rates.
 During the Baby Boom (1946-1962) TFR reached 3.7
children per woman.
 The baby bust of the 1970’s that followed the baby boom of
the 50’s and 60’s was largely due to delayed marriage, more
women entering the workforce, contraception, and abortion.
Case Study:
The U.S. Population Is Growing Rapidly
http://2010.census.gov/2010census/data
Several Factors Affect Birth Rates
and Fertility Rates
 The number of children women have is affected by:
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Importance of children as part of labor force
The cost of raising and educating them
Urbanization
Education and employment opportunities for women
Infant deaths
Marriage age
Availability of contraception and abortion
Religious beliefs, traditions, cultural norms
Several Factors Affect Death Rates
 The rapid growth of the world's population has not
been because of increasing birth rates.
 It is because of a rapid decrease in death rates.
• Life expectancy – the number of years a newborn
infant can expect to live.
 Death rates have declined because of:
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Increased food supplies, better nutrition
Advances in medicine
Improved sanitation and personal hygiene
Safer water supplies
Several Factors Affect Death Rates
 Infant mortality rate
the number of infants
out of every 1,000
who die before their
first birthday.
 U.S. infant mortality is higher than it should be
(ranked 46th world-wide) due to:
• Inadequate pre- and post-natal care for poor
• Drug addiction
• High teenage birth rate
 This rate has dropped by almost half from 1991-2006
Migration Affects an Area’s Population Size
Case Study: The United States: A Nation of Immigrants
 Since 1820, the U.S. has
admitted almost twice as
many immigrants and
refugees as all other
countries combined.
 Most migrants seek jobs and
economic improvements.
 Others come to escape
religious, ethnic, or political
oppression.
 Environmental refugees – people driven out of an
area as a result of environmental degradation.
• Water shortage, pollution, rise in ocean level, etc.
6-3 How Does a Population’s Age Structure
Affect Its Growth or Decline?
 Concept 6-3 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?
 The number of people in young, middle, and older
age groups determines how fast populations grow
or decline.
 Age structure categories:
• Pre Reproductive, Reproductive, Post Reproductive
 The number of people younger than age 15 is the
major factor determining a country’s population
growth – they are future reproducers.
 Changes in the distribution of a country’s age
groups have long-lasting economic, social, and
environmental impacts.
Populations Can Grow, Shrink,
or Remain Stable
 The proportion of individuals at various ages is the
population’s age structure.
• Pre-reproductive age: not mature enough to reproduce.
• Reproductive age: those capable of reproduction.
• Post-reproductive age: those too old to reproduce.
 How fast a population grows or declines depends on
its age structure:
• Young populations can grow fast
• Old populations decrease over time
• Even age distribution will result in constant population size
Generalized Population Age Structure Diagrams
 Populations with a large proportion of its people in
the pre-reproductive ages of 1-14 yrs have a large
potential for rapid population growth.
A Reminder From Chapter 1:
Developed vs. Developing Countries
The United Nations classifies the world’s countries into as
developed or developing based one their level of industrialization
and their per capita GDP.
Population Structure by Age and Sex in
Developing and Developed Countries
 Nearly 28% of the world’s population (1.9 billion) were
under 15 years old in 2008.
 Includes 30% of the people in developing countries versus
only 17% in developed countries.
Tracking the Baby-Boom Generation
in the United States
 Today, baby boomers make up nearly half of all
adult Americans and dominate the populations
demand for goods and services.
Populations Made Up of Mostly
Older People Can Decline Rapidly
 About 14% of the world’s population live in countries
with stabilizing or declining populations.
• Japan, Russia, Germany, Italy, Spain, Hungary, Poland,
Greece, Ukraine, Czech Republic
 Slow decline is manageable
 Rapid population decline can lead to long-lasting
economic and social problems.
Populations Made Up of Mostly
Older People Can Decline Rapidly
 Rapid population
decline can put
severe strains on a
country’s budget
since older people
consume a larger
share of medical
care, social security
funds, and other
public services that
are paid for by a
decreasing number
of taxpayers.
Populations Can Decline from a Rising
Death Rate: The AIDS Tragedy
 Death from AIDS can disrupt a country’s social and
economic structure by removing significant numbers of
young adults.
 25 million killed by 2008
 Sharp drop in life expectancy
 Many young adults die:
• loss of most productive workers
 International community called upon to:
• Reduce the spread of HIV through education and health care
• Financial assistance and volunteers
6-4 How Can We Slow Human Population Growth?
 Concept 6-4 Experience indicates that the most
effective ways to slow human population growth
are to encourage family planning, to reduce
poverty, and to elevate the status of women.
As Countries Develop, Their Populations
Tend to Grow More Slowly
 Demographic Transition: As countries become
economically developed, their birth and death rates
tend to decline.
• Preindustrial stage: high infant mortality – results in low
population growth rate
• Transitional stage: industrialization begins, death rates
drops while birth rates remain high – results in high
population growth rate
• Industrial stage: birth rate drops and approaches death
rate – results in small population growth
• Postindustrial stage: birth rate declines even further and
can be equal to or less than the death rate – results in no
growth or even a decline
Four Stages of the Demographic Transition
6-4 How Can We Slow Human Population Growth?
 The best way to slow population growth is a
combination of:
• Investing in family planning – deciding when and how
to have children, use of contraception
• Reducing poverty – poor families have more children
to help with work or in case some die
• Elevating the status of women – educated, working
women who are involved in the decision making
process have less children
Case Studies:
Population Growth in China and India
China = 1.35 billion people (20% of world’s pop.)
 Since 1970, China has used a government-enforced
program to cut its birth rate in half and sharply
reduce its fertility rate.
India = 1.27 billion people (17% of world’s pop.)
 For more than five decades, India has tried to control
its population growth with only modest success.
Slowing Population Growth in China:
the One-Child Policy
 Currently, China’s TFR is 1.6 children per women.
 China has moved 300 million people out of poverty.
 Problems:
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Controversial “One Child”
policy – couples lose social
and economic benefits if they
have more than one child
Strong male preference leads
to gender imbalance
Average population age is
increasing
Not enough resources to
support population
Case Study:
Slowing Population Growth in India
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Poor planning
Bureaucratic inefficiency
Low status of women
Extreme poverty
Lack of administrative
financial support
 Disagreement over the
best ways to slow
population growth