CHAPTER 6
THE HUMAN POPULATION AND URBANIZATION
Outline
6-1 How many people can the earth support?
A. Human population growth continues but it is unevenly distributed.
1. For most of history, the human population grew slowly, but has been growing exponentially
for the past 200 years. Reasons for this increase in growth rate include:
2. The rate of population growth has slowed, but the world’s population is still growing at a rate
that added about 83 million people during 2011.
3. Geographically, this growth is unevenly distributed.
a. About 1% of the 83 million new arrivals on the planet in 2011 were added to the world’s
4. SCIENCE FOCUS: How long can the human population keep growing?
5. Cultural carrying capacity is the maximum number of people who could live in reasonable
6-2 What factors influence the size of the human population?
A. The human population can grow, decline, or remain fairly stable.
1. Birth rate, or crude birth rate, is the number of live births per 1,000 people in a population in a
given year.
2. Death rate, or crude death rate, is the number of deaths per 1,000 people in a population in a
given year.
3. Population change of an area = (births + immigration) – (deaths + emigration).
B. Women are having fewer babies but not few enough to stabilize the world’s population.
2. Between 1955 and 2011, the average global lifetime number of births of live babies per
woman dropped from 5 to 2.5.
3. A TFR of 2.1 will eventually halt the world’s population growth.
C. CASE STUDY: The U.S. population is growing.
1. The population of the United States grew from 76 million in 1900 to 312 million in 2011.
3. TFR has dropped in the U.S. since the peak during a peak during the baby boom of 3.7
children per woman to at or below 2.1 children per woman in most years from 1972 to 2011.
4. The U.S. population is still growing faster than all other more-developed countries as well as
that of China. About 2.7 million people were added to the U.S. population in 2011, with about
5. Lifestyle changes since 1900 include a dramatic increase in per capita resource use and a
much larger U.S. ecological footprint.
D. Several factors affect birth rates and fertility rates.
1. A particular country’s average birth rate and TFR can be affected by:
a. The importance of children as a part of the labor force.
b. The cost of raising and educating children.
2. Several factors affect death rates.
a. People started living longer and fewer infants died because of increased food supplies
and distribution, better nutrition, medical advances, improved sanitation, life
expectancy, married women working, and safer water supplies.
b. Two useful indicators of the overall health of people in a country or region are life
expectancy (the average number of years a person can expect to live) and infant
mortality rate (the number of babies out of every 1,000 born who die before their first
birthday).
i. The average global life expectancy increased from 48 years in 1955 to 69
years in 2011. Between 1900 and 2011, the average global life expectancy
in the United States increased from 47 years to 78 years.
ii. Infant mortality is a measure of a society’s quality of life because it reflects
E. Migration affects an area’s population size.
1. Migration is the movement of people into (immigration) and out of (emigration) specific
geographic areas.
2. CONNECTIONS: Global Warming and Environmental Refugees.
3. CASE STUDY: The United States: A Nation of Immigrants.
a. Since 1820, the United States has admitted almost twice as many immigrants and
refugees as all other countries combined.
b. Legal and illegal immigration account for about 36% of the country’s annual population
growth.
Chapter 6: The Human Population and Urbanization
c. Between 1820 and 1960, most legal immigrants to the United States came from Europe.
Since 1960, most have come from Latin America and Asia. Hispanics are projected to
make up 30% of the U.S. population by 2050.
d. There is controversy over reducing legal immigration to the U.S.
i. Proponents of reducing immigration say it would help stabilize population
size and reduce the country’s enormous environmental impact.
6-3 How does a population’s age structure affect its growth or decline?
A. A population’s age structure helps us to make projections.
2. Population age-structure diagrams are made by plotting the percentages or numbers of males
and females in the total population in each of three age categories:
3. Demographic momentum is rapid population growth in a country that has a large percentage
4. 1.8 billion people will move into their reproductive years by 2025.
6. The global population of seniors (age 65 and older) is increasing due to declining birth rates
and medical advances that have extended life spans.
B. CONNECTIONS: The American baby boom
1. The American baby boom added 79 million people to the U.S. population between 1946 and
2. The large numbers of baby boomers have strongly influenced the U.S. economy. First they
created a youth market and are now creating the late middle age and senior markets.
4. As the number of working adults declines in proportion to the number of seniors, so will the
tax revenues necessary for supporting the growing senior population.
C. Populations made up mostly of older people can decline rapidly.
1. Japan has the world’s highest percentage of elderly people and the world’s lowest percentage
2. The average age of China’s population is increasing at one of the fastest rates ever recorded.
This could lead to a declining work force, higher wages for workers, limited funds for
supporting continued economic development, and fewer children and grandchildren to care
for the growing number of elderly people.
D. Populations can decline from a rising death rate: the AIDS tragedy.
1. Between 1981 and 2010, AIDS killed more than 29 million people, and it takes about 2
million more lives each year (22,000 in the United States).
2. AIDS kills many young adults and leaves many children orphaned, causing a change in the
young-adult age structure of a country. This causes a sharp drop in average life expectancy,
3. AIDS can cause a pandemic loss of productive young adult workers and trained personnel.
6-4 What are some ways to slow human population growth?
A. header that still needs to be written
1. The three most effective ways to slow or stop population growth are to reduce poverty,
elevate the status of women, and encourage family planning and reproductive health care.
B. Promote economic development.
1. As countries become industrialized and economically developed, their populations tend to
grow more slowly. This demographic transition has four phases:
2. Less-developed countries may transition to slower growth if modern technology can raise per
capita incomes by bringing economic development and family planning.
3. Rapid population growth, extreme poverty, and increasing environmental degradation in some
low-income less-developed countries—especially in Africa—could leave these countries
stuck in stage 2 of the demographic transition.
C. Empowering women can slow population growth.
1. Women tend to have fewer children if they are educated, have the ability to control their own
3. Women make up 70% of the world’s poor and 64% of its 800 million illiterate adults.
4. Poor women who cannot read often have an average of 5–7 children, compared to 2 or fewer
children in societies where almost all women can read.
D. Promote family planning.
2. Successes of family planning:
a. Without family planning programs that began in the 1970s, the world’s population
3. Problems that have hindered success in some countries:
a. 42% of all pregnancies in less-developed countries are unplanned and 26% end with
4. CASE STUDY: Slowing Population Growth in India.
a. For over 50 years, India has tried to control its population growth with only modest
success.
6-5 What are the major urban resource and environmental problems?
A. header that still needs to be written
1. An increasing percentage of the world’s people live in urban areas.
2. Urban areas grow in two ways—by natural increase due to births and by immigration, mostly
3. Three major trends in urban population dynamics have emerged:
a. The proportion of the global population living in urban areas increased from 2% in 1850
to 50% today, and is projected to be 70% by 2050.
b. The numbers and sizes of urban areas are mushrooming. We now have cities with 10
B. CASE STUDY: Urbanization in the United States.
1. Between 1800 and 2011, the percentage of the U.S. population living in urban areas increased
from 5% to 79%. This population shift has occurred in four phases.
2. There are upsides to urbanization. Conditions in U.S. cities have improved, with better
4. Many cities have aging infrastructures (streets, bridges, dams, power lines, schools, waste
management, water supply pipes, and sewers) with limited funds for repair.
C. Urban sprawl gobbles up the countryside.
1. Urban sprawl, or the growth of low-density development on the edges of cities and towns, is
eliminating surrounding agricultural and wild lands.
3. Urban sprawl has caused or contributed to a number of environmental problems.
a. People are forced to drive everywhere, resulting in more emission of greenhouse gases
and air pollution.
D. Urbanization has advantages.
1. Cities are centers of industry, commerce, transportation, innovation, education, technological
advances, and jobs.
3. Cities provide better access to medical care, family planning, education, and social services.
5. Concentrating people in cities helps to preserve biodiversity.
6. Central cities can save energy if residents rely more on energy efficient mass transportation,
walking, and bicycling.
E. Urbanization has disadvantages.
1. Most urban areas are unsustainable systems.
a. The typical city depends on large non-urban areas for huge inputs of matter and energy
resources, while it generates large outputs of waste matter and heat.
2. Most cities lack vegetation.
3. Many cities have water problems.
a. Providing water to cities can deprive rural and wild areas of surface water and can
deplete underground water supplies.
b. Cities in arid areas that depend on water withdrawn from rivers and reservoirs behind
dams will face increasing problems.
c. Cities can have flooding problems for several reasons:
i. Being built on floodplains or near low-lying coastlines.
ii. Covering land with buildings, asphalt, and concrete causes precipitation to
4. Cities tend to concentrate pollution and health problems.
a. Cities produce most of the world’s air pollution, water pollution, and solid and
5. Cities affect local climates.
a. Cities tend to be warmer, rainier, foggier, and cloudier.
6. Life is a desperate struggle for the urban poor in less-developed countries.
a. At least 1 billion people live under crowded and unsanitary conditions in cities in less-
developed countries.
b. Slums are areas dominated by tenements and rooming houses where several people
F. CASE STUDY: Mexico City.
1. The world’s second most populous city suffers from severe air pollution, high unemployment,
2. Air and water pollution cause an estimated 100,000 premature deaths per year.
3. The severity of air pollution has been reduced by banning cars in its central zone, requiring air
6-6 How does transportation affect urban environmental impacts?
A. Cities can grow outward or upward.
1. Most people living in compact cities such as Hong Kong, China, and Tokyo, Japan, get
around by walking, biking, or using mass transit such as rail or buses.
2. In countries such as the United States, Canada and Australia, plentiful land and networks of
3. Largely because of urban sprawl, all Americans combined drive about the same distance each
year as the total distance driven by all other drivers in the world, and in the process use about
43% of the world’s gasoline.
B. Motor vehicles have advantages and disadvantages.
2. They can be symbols of power, sex appeal, social status, and success.
4. Globally, automobile accidents kill approximately 1.2 million people a year and injure
another 15 million people.
6. Motor vehicles are the world’s largest source of outdoor air pollution.
8. At least a third of the world’s urban land and half of that in the United States is devoted to
roads, parking lots, gasoline stations, and other automobile-related uses.
9. People waste time sitting in traffic congestion.
C. Reducing automobile use is not easy, but it can be done.
1. A user-pays approach makes drivers pay directly for most of the environmental and health
costs caused by their automobile use.
a. An example of full-cost pricing is a tax on gasoline that covers the estimated harmful
2. Raise parking fees and charge tolls on roads, tunnels, and bridges leading into cities,
especially during peak traffic times.
3. Some cities promote car-sharing networks, which bill members monthly for the time they use
a car and the distance they travel, and can decrease car ownership.
D. Some cities promote alternatives to cars
1. The following are alternatives to cars, each with its own advantages and disadvantages (see
Figs. 6-19 – 6-22).
6-7 How can cities become more sustainable and livable?
A. We can make urban areas more environmentally sustainable and enjoyable places to live.
1. Smart growth encourages environmentally sustainable development requiring less dependence
2. New urbanism involves less-developed villages within cities, so that people can live within
walking distance of where the work, shop, and go for entertainment
B. CASE STUDY: The new urban village of Vauban
2. Street parking, driveways, and garages are generally forbidden in the village. A parking space
in a city garage costs $40,000.
3. Homes are within easy walking distance of trains, stores, banks, restaurants, and schools.
4. There are no single-family homes, only energy-efficient row houses that use passive solar
energy.
5. A ecocity, or green city, like Vauban, emphasizes the following goals:
Instructor’s Manual for Environmental Science, 15th edition
a. Use solar and other locally available, renewable energy resources and design buildings
6. Current examples of ecocities include Curitiba, Brazil; Bogotá, Colombia; Waitakere City,
New Zealand; Stockholm, Sweden; Helsinki, Finland; Leicester, England; the Netherlands;
and in the United States, Portland, Oregon; Davis, California; Olympia, Washington; and
Chattanooga, Tennessee.
C. CASE STUDY: The ecocity concept in Curitiba, Brazil.
1. A city of 3.2 million people known as the “ecological capital” of Brazil.
2. Planners in this city in 1969 focused on an inexpensive and efficient mass transit system
rather than on the car.
3. Only high-rise apartment buildings are allowed near major bus routes, and each building must
devote its bottom two floors to stores, reducing the need for residents to travel.
5. The city transformed flood-prone areas along its six rivers into a series of interconnected
parks.
6. Curitiba recycles roughly 70% of its paper and 60% of its metal, glass, and plastic. Recovered
8. About 95% of Curitiba’s citizens can read and write and 83% of its adults have at least a high
school education. All school children study ecology.
9. This chapter’s three big ideas are:
a. The human population is increasing rapidly and may soon bump up against
environmental limits.
Objectives
6-1 How many people can the earth support?
CONCEPT 6-1 The continuing rapid growth of the human population and its impact on natural capital raises
questions about how long the human population can keep growing.
6-2 What factors influence the size of the human population?
CONCEPT 6-2A Population size increases through births and immigration and decreases through deaths and
emigration.
1. Define birth rate, death rate, emigration rate, and immigration rate. Write an equation to
mathematically describe the relationship between these rates and the rate of population change.
CONCEPT 6-2B The key factor that determines the size of a human population is the average number of
children born to the women in that population (total fertility rate).
1. Define total fertility rate. Describe how fertility rate affects population growth. List eight factors that
affect birth rates and fertility rate.
3. Define life expectancy and infant mortality. List three factors that can increase rates of infant mortality.
4. Describe population growth in the United States. Include a description of changes in immigration
patterns.
6-3 How does a population’s age structure affect its growth or decline?
CONCEPT 6-3 The number of males and females in young, middle, and older age groups determines how fast
a population grows or declines.
1. Define age structure. Using population age structure diagrams, explain how the age structure of a
3. Define population decline, give two examples and describe problems associated with a declining
population.
6-4 What are some ways to slow human population growth?
CONCEPT 6-4 We can slow human population growth by reducing poverty through economic development,
elevating the status of women and encouraging family planning.
1. List a few approaches to slowing human population growth. Define demographic transition and list its
2. Summarize India’s experiences with family planning.
6-5 What are the major urban resource and environmental problems?
CONCEPT 6-5 Most cities are unsustainable because of high levels of resource use, waste, pollution, and
poverty.
2. Define urban sprawl. List several advantages and disadvantages of urbanization.
4. Describe conditions in Mexico City and efforts made to reduce its air pollution.
6-6 How does transportation affect urban environmental impacts?
CONCEPT 6-6 In some countries, many people live in dispersed urban areas and depend mostly on motor
vehicles for their transportation, which greatly expands their ecological footprints.
2. List four alternative forms of transportation to the car, and evaluate the advantages and disadvantages
of each.
6-7 How can cities become more sustainable and livable?
CONCEPT 6-7 An eco-city allows people to choose walking, biking, or mass transit for most transportation
needs; to recycle or reuse most of their wastes; to grow much of their food; and to protect biodiversity by
preserving surrounding land.
2. Define eco-city and list eight goals of an eco-city. Describe the eco-city of Curcibita, Brazil.
3. List the chapter’s three big ideas.
Instructor’s Manual for Environmental Science, 15th edition
Key Terms
age structure
death rate
demographic transition
family planning pg.
infant mortality rate
life expectancy
migration
population change
smart growth
total fertility rate TFR
urban sprawl
Teaching Tips
Use the Core Case Study on population growth in China to introduce the notion that planned dedication to
decreasing population growth is critical for change to truly occur, and that if the changes are well designed,
citizens will want to be a part of change rather than be part of the resistance to change. Ask students if they
live in a highly or sparsely populated area.
• Have the students list the advantages and disadvantages to living in their respective areas.
• In addition, ask students how the humans in their city or town are affecting the natural ecosystem.
• Discuss how their town or city may go green and what effects this may have on the environment
and the human population.
Examine your own campus’ sustainability.
• Find out the population number, and when the population is present on campus.
• List the current environmentally positive practices.
• How can any individual, or a group like your class, help influence effective changes?
Paper Topics
1. How does population growth impact sustainability?
a. Compile a case study of population growth and sustainability in Mexico, China, India, or
Kenya.
b. Discuss one of the following topics as it relates to population growth and sustainability:
2. What are the environmental impacts of population on: air pollution in urban areas, land degradation
from urban sprawl, deforestation and desertification in less-developed countries?
3. How do India, China, and Japan control their populations compared to the United States?
6. Do you think the United States should play a global leadership role in promoting stabilization of the
world’s human population?
7. What decisions should individuals be able to make about family size and urban conditions? List the
8. What changes in urban planning can decrease the negative impacts of urban sprawl? How can cities be
designed so that automobile use is decreased? What are some of the challenges faced in promoting
other methods of transportation?
9. How can urbanization embrace self-sustainable cities, especially as rural to urban migration patterns
increase? Use the case study in sustainable living from Brazil to draw examples.
Activities and Projects
1. Invite a public health official or nutritionist to your class to explain the factors involved in the decline
in the global death rate over the past century and the decline in the infant mortality rate in the United
States. Why is the latter rate higher in the United States than in many other developed nations?
2. U.S. immigration policy had become a volatile political issue by the 1980s. Arrange a debate on this
3. Ask your students to share with the class poems, short stories, songs, paintings, collages, photographic
4. Are there family planning clinics in your community that provide contraceptives and birth control
counseling? Invite a family planning worker to visit your class and discuss the birth control aspects of
5. As a class project, investigate the fate of agricultural land in your city’s vicinity. Is anything being
done to prevent prime agricultural land from being overtaken by urban sprawl?
6. Survey the marriage and childbearing intentions of your female students. Find out at what age
7. Survey your students to obtain age or lifespan information about their grandparents. Compare the
8. As a class, research the environmental impact of the growing populations of less-developed countries
and more-developed countries. For representative more-developed and less-developed countries, find
9. Have your students analyze the political platforms of the major political parties in the United States.
What positions do they take on the birth of American children and birth control? What positions do
Instructor’s Manual for Environmental Science, 15th edition
they take on the influence of the United States in global population growth patterns? To what extent
does debate on population policy revolve around right to life, desired pregnancies, and quality of life
for the children who are born?
Attitudes and Values Assessment
1. Do you feel the size of the human population is an important environmental issue?
2. Do you feel consumption by the human population is an important environmental issue?
3. Do you feel that humans have the right to have as many children as they want? Are there any limits on
this right? If so, what are they?
4. Do you feel that there should be a national population policy? What steps would you support?
5. Do you feel that teen pregnancy is a problem?
6. Do you feel that women’s roles are important in addressing population size?
7. What are your feelings about birth control? Population control?
Laboratory Skills
Wels, Edward. Lab Manual for Environmental Science. 2009. Lab #2 The Tragedy of the Commons – A
Classroom Simulation Exercise.
Wells, Edward. Lab Manual for Environmental Science. 2009. Lab #3: Population Growth.