Chapter 2 Population Growth
Chapter Outline
1) Why Should You Care about Population Growth?
a) The human population is 7 billion
i) Each year it grows by 83 million
ii) There are two major reasons for concern
(1) More people puts more pressure on natural resources and natural chemical cycling
(a) As per capita income increases, per capita resource use increases
(2) Our ecological footprints are degrading our life-support system
(a) Despite expanding ecological footprints, 1.4 billion people live in extreme poverty
2) What Do You Need to Know?
a) Exponential growth is the growth of any quantity at a fixed percentage per unit of time
i) Starts slowly then increases dramatically
(1) It took from ~200,000 years ago until the year 1800 for the human population to reach 1 billion
(2) The second billion was added in 130 years (1930)
(3) The third billion took 30 years (1960)
(4) The fourth billion took 14 years (1974)
(5) Now, a billion is added every 12-13 years
(6) Graphed as a J-Curve
ii) Unlimited exponential growth is kept in check by limiting factors
(1) Availability of resources and threats to survival
(2) Limiting factors act together to determine the carrying capacity, the maximum population that
an environment can sustain
(3) As a population nears the carrying capacity of its environment, its rate of growth typically slows,
becoming an S-curve on a graph
iii) Populations that exceed their environment’s carrying capacity experience a population crash
b) The human population has experienced exponential growth as a result of three factors
i) We learned to use coal, oil and other energy sources
ii) Modern agriculture
iii) Improved sanitation and health care
c) The exponential rate of population growth is declining and is just over 1% as of 2012
i) It was 2% in 1965
ii) Population growth is unevenly distributed between rich and poor countries
iii) More-developed countries account for only 1/80 births
iv) Less-developed countries account for the other 79 births
(1) 82% of the global population lives in less-developed countries
v) China has the world’s largest population (1.4 billion) followed by India (1.3 billion)
(1) The United States accounts for only 4.5% of the global population
d) Three factors influence population growth: births, deaths, and migration
i) Population change = (births + immigration) – (deaths + emigration)
ii) Total fertility rate is the average number of children born to women of a population
(1) TFR’s tend to be higher in less-developed countries
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(a)
(b)
(c)
(d)
Families rely on children to care for them into old age
Infants are more likely to die
More children can contribute more work
TFRs are higher where women lack education, employment opportunities, and access to
family planning services
iii) Life expectancy is the average years a person in a population lives
(1) Between 1955 and 2012 global life expectancy rose from 48 to 70 years
iv) Infant mortality rate is the number of babies per 1000 born that die within the first year
(1) Excellent measure of a society’s quality of life (as it is related to health care and nutrition)
(2) From 1965 to 2012 infant mortality dropped from 20 to 6 in more-developed countries and from
118 to 48 in less-developed countries
v) The United States experienced a baby boom from 1946 to 1964, growing by 79 million people
(1) TFR was 3.7 at the peak, in 1957
(2) Population growth in the U.S. has slowed but is still growing faster than other more-developed
countries
(3) Projected to reach 423 million by 2050
(a) Immigration will account for 1/3 of that growth
e) Age structure (the percentage of the population in different age groups) determines whether a
population will grow or shrink in the future
i) Represented by age structure diagrams, representing the proportion of the population in 3 age
groups
(1) Pre-reproductive (0-14)
(2) Reproductive (15-44)
(3) Post-reproductive (45 and older)
ii) Populations increase when most people are in or about to enter the reproductive stage
iii) It will drop when most are post-reproductive
iv) It will remain stable when there is equal distribution among all three groups
f) ~29% of people in less-developed countries are under 15, compared with 16% for more-developed
countries
g) A change in distribution amongst age groups can have lasting social and economic impacts
i) As baby boomers move into retirement they will put strain on the Social Security and Medicare
systems
ii) Populations can decline as more people move into the post-reproductive class
iii) Can lead to labor shortages and fewer people paying taxes to support public services
3) What Are the Problems?
a) The tragedy of the commons – occurs when the number of users and their rate of resource use outpaces
the rate of replenishment leading to resource depletion
i) Aquifers, topsoil, mineral resources, the overexploitation of wild species, deforestation and rising
levels of CO2 in the atmosphere are all examples
b) Ecological tipping points occur when environmental degradation causes an irreversible tipping point
c) People in more-developed countries consume more resources and generate more pollution and waste
than people in less-developed countries do, per capita
i) IPAT model compares these impacts based upon population size (P), affluence or per capita
consumption (A), the harmful or beneficial effects of technology (T).
ii) Impact (I) = Population (P) x Affluence (A) x Technology (T)
iii) Two major types of impacts
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(1) Overpopulation impacts occur when population size is the biggest factor
(2) Overconsumption impacts occur when affluence is the biggest factor
(3) When countries with large populations grow in affluence environmental impacts will grow
sharply
d) The size of earth’s carrying capacity is debatable
i) It is estimated that humanity’s ecological footprint may be 30% higher than earth’s long term
capacity to support us
ii) We potentially face two consequences if we fail to reduce population growth and resource
consumption
iii) In some areas environmental conditions will deteriorate and death rates will rise
iv) A growing population of consumers will expand ecological footprints
4) What Can Be Done?
a) Demographic transition is a four-phase process whereby a country’s population growth rate declines
i) Stage 1 – Pre-Industrial: Slow growth because of high birth rates and high death rates
ii) Stage 2 – Transitional: Rapid growth because of high birth rates and decreasing death rates
iii) Stage 3 – Growth slows as birth rates and death rates drop
iv) Stage 4 – Growth levels then begins to decline as birth rates equal then fall below death rates
(1) Developing countries may undergo demographic transition or may become mired in a
transitional phase
v) Women have fewer children when they have access to family planning and employment
(1) In many cases, women tend to have fewer rights and limited access to education
b) Poverty occurs when people are unable to meet their basic needs
i) Reducing poverty reduces the need to overexploit resources and tends to slow population growth
ii) The UN Millennium Development Goals include sharply reducing poverty and hunger, improving
health care, empowering women, and providing education more universally by 2015
(1) Most nations have not met their annual monetary pledge to achieve these goals
(2) Business and governments can assist by funding projects and providing micro-loans
c) Making A Difference
i) In 1983, Muhammad Yunus started Grameen Bank in Bangladesh
(1) Provides microloans of $100-1000 at low interest rates
(2) Borrowers are put into groups of five who are responsible for one another’s repayment
(3) Half of the borrowers have moved above the poverty line within five years
(4) In 2006, Yunus and his colleagues won a Nobel Prize for pioneering microcredit
d) Family planning is an important step in making the demographic transition
i) Has played a major role in reducing birth rates, the number of abortions, and the number of deaths of
mothers and fetuses during pregnancy
ii) Despite this success, there are two problems
(1) 42% of pregnancies in less-developed countries are unplanned and more than half end in
abortion
(2) In less-developed countries, family planning programs are not available to 160 million couples
that want them
e) Making a Difference
i) Thailand reduced its population growth very quickly through government supported family planning
ii) In 1971, the population was growing at 3.2%/year, which fell to 1.6% in 15 years and 0.5% by 2012
iii) Due to strong support for family planning by government as well as Buddhist leaders and high literacy
among women. Also, grassroots activism by Mechai Viravaida
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f)
Without taking steps to limit population growth, there may be an increase in environmental refugees –
those who are homeless of starving due to environmental degradation
g) For Instance: India established the world’s first national family planning program in 1952 with moderate
success
i) It is projected to become the world’s most populous nation by 2015
ii) About 76% of the population is poor to very poor
iii) Despite family planning efforts, TFR is 2.6 and only 47% of couples use birth control
iv) Two factors contribute to large family size
(1) Extensive poverty
(2) Strong cultural preference for male children
h) China promotes one-child families
i) The government provides contraceptives, sterilization and abortions for married couples. Those who
pledge to have only one child receive benefits including better housing, health care and job
opportunities
ii) Between 1972 and 2012, TFR was reduced from 5.7 to 1.5
iii) China has the world’s largest population
iv) Since 1980 China has undergone rapid economic growth
v) This strategy has resulted in a strong preference for male children and a change in age structure
i) Population growth and environmental degradation are creating environmental refugees
i) 25 million in the mid-1990s; 40 million in 2011
ii) Due to climate change, this number could reach 250 million or beyond
iii) Some agencies are reluctant to officially recognize environmental refugees
(1) Growing numbers of environmental refugees may pose threats to international stability and
peace
5) What Would You Do?
a) Some steps people are taking
i) Thinking more carefully about number of children
ii) Support efforts to slow population growth
iii) Reducing personal ecological footprints
Objectives
Exponential growth – explain exponential growth in biological populations
Human population growth – describe the history and demographics of human population growth
Dynamics – summarize the dynamics and key features of human population growth
Ecological footprints – relate the concept of ecological footprint to human population growth and
resource consumption
IPAT – Discuss the IPAT model
Economic development – assess the roles of economic development and family planning in population
stabilization
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Environmental refugees - identify key attributes and implications of environmental refugees
Key Terms
Age structure
Carrying capacity
Demographic transition
Ecological tipping point
Environmental refugees
Exponential growth
Family planning
Infant mortality rate
IPAT model
Less-developed country
Life expectancy
Limiting factors
Migration
More-developed country
Overconsumption impacts
Overpopulation impacts
Poverty
Total fertility rate (TFR)
Talking Points/Discussion
What factors would determine the carrying capacity for humans on earth?
What are the advantages and disadvantages of China’s One Child Policy?
Should we work to slow population growth or reduce ecological footprints?
Term Paper Research Topics
Choose a strategy that has been successful in slowing population growth, be it family planning,
education, microlending, etc. Research the objectives of this approach, any controversy surrounding it,
and its successes and failures.
Choose a limiting factor, such as water, and discuss how the current population is taxing it and what the
prospects hold for the future.
Compare a more-developed nation that has a growing population with one that has a declining
population. What are their differences and what could be the cause of their very different population
trajectories?
Class Activities and Projects
Given that the human population is growing, the best way to mitigate the effects of excessive resource
use is to lessen per capita ecological footprints. Brainstorm ways in which this could be done. As a class,
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or as individual groups, take the challenge to reduce some aspect of your footprint. Do this for a week
and then report back to the class.
The population in your class of lecture hall has grown dramatically and shows no sign of stopping. You
are at risk of running out of space. What approach would you as a group agree is the best for limiting
future growth?
Design a survey about the effects of human population growth, its current trends and future projected
growth. Working in groups, survey the population outside of the class and report back on the general
public’s knowledge and understanding of the broader implications of human population growth.
Digital Integration
Correlation to Explore More
Exponential Growth
Human Population Change
Mass Transit
Population Dynamics
Environmental Ethics
Environmental Impacts
Correlation to Global Environment Watch
Consumption
Family Planning
Globalization
Migration of People
Overpopulation
Suggested Answers to End of Chapter Questions
Thinking Critically
1. What would you say if someone asked you why he or she should care about population growth in
the world and in his or her own country? What about you? Do you really care about how many
people there are on the earth, in your country, or in the area where you live? Explain.
The response should include a discussion of the impact that more people have on the earth’s life
support systems. More people means more consumption of both renewable and non-renewable
resources, as well as increased pressure on the cyclical systems that feed into our life support
systems. Acknowledging that there are limits to how many people can be supported on earth, it
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follows that more people will tax the system in a way that allows less for each individual person in
the population. Furthermore, as economic development ensues resulting in increased affluence,
each person will have a greater ecological impact and will demand more of the already limited
resources and taxed cycles.
2. On average, how many people are added to the world’s human population every second? Using this
current rate, calculate how many people will likely be added to the population by the time you reach
the age of 70. Do you believe that this number of people will be within the earth’s carrying capacity
for humans? Explain.
The text states that the human population grows by 227,000 per day. 227,000/24 hours =
9458/hour. 9458/ 60 minutes = 158 people/minute. 158/60 seconds = 2.6 people per second.
Assuming that a student is 20 years old, the population growth will be calculated for 50 years.
50 years x 365 days x 24 hours x 60 minutes x 60 second x 2.6 people = 4,099,680,000 (just over 4
billion people)
This is likely well beyond the earth’s carrying capacity for humans, especially as fossil fuels become
increasingly scarce, making agriculture less productive.
3. Should everyone have the right to have as many children as they want? Explain. Would you support
this right even if it degrades the earth’s life support systems and makes it harder for future
generations to live comfortably?
Answers will vary by student.
4. Why do you think reducing poverty tends to slow population growth? Think of at least three
reasons and explain.
Population growth slows with poverty reduction because people have better access to education
and family planning, people feel less need to have many children who can help work and care for
them into old age, and there is less likelihood of infant mortality.
5. Why do you think there has been little effort to reduce population growth in the United States?
Would you support or oppose efforts to slow population growth in the United States? Explain. If
you support slowing this growth, what are three strategies that you think might be useful for
accomplishing this?
Student answers will vary. In recent history, the total fertility rate has been at or below 2.1 children,
which is right at replacement fertility. Immigration also plays a role in overall population growth.
6. Considering the major requirements in your life (such as food, transportation, and housing), in what
ways do you think you could or should reduce your ecological footprint? List the steps you could
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take to begin making these changes. If you do not believe that you should do this, explain your
thinking.
Student answers will vary.
Global Environmental Watch Assignment Template
Countries of the World: Power Point Oral Presentation
NAME_____________________________________ CLASS_____________________ SECTION______________
Countries of the World
Power Point Oral Presentation
This assignment will help you appreciate and understand the global interrelatedness of the environment
and the similarities and differences of environmental issues between countries.
Instructions:
 You will give a 5 – 10 minute power point presentation about a particular country. Include
statistical information, as well as choose three environmental issues facing that country and
discuss the problems and possible solutions. Solutions may include those legislated by
government, as well as those of private individuals or companies.
 Once on the country page (in GREENR), the right side of the page contains “quick facts” related
to that country’s environmental impacts. Also, the overview will be helpful to give a broad view
of the nation. This can assist you in narrowing the focus to determine the three environmental
issues to research and discuss.
 Topic Portal: Using the Basic Search function, type in the assigned country. You will then be
directed to that country’s portal.
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TITLE
DESCRIPTION
TYPE
OF
EXERCISE
TYPE
OF
ASSET
Countries of the World
Students will give a 5 – 10 minute power point presentation about a particular country.
They will include statistical information, as well as choose three environmental issues
facing that country and discuss the problem and possible solutions. Solutions may include
those legislated by government, as well as those of private individuals or companies.
Power Point Oral Presentation
Basic Search function to access the portal for the assigned country.
Help students to appreciate the global interrelatedness of the environment, as well as an
understanding of similarities and differences of environmental issues between countries.
OBJECTIVES
LINK
TO
PORTAL/
DOCUMENT
ADDITIONAL
INSTRUCTIONS
Students will give an overview of the country, report on some quick facts, and choose
three environmental issues of that nation and discuss.
Using the Basic Search function, type in the assigned country.
Once on the country page, the right side of the page gives numerous “quick facts” related
to that country’s environmental impacts. Also, the overview will be helpful to give
students a broad view of the nation. This can assist the student in narrowing their focus
to determine the three environmental issues they must research and discuss.
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