3. Human Population Growth
Continues But it is Unevenly
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
Humans have expanded into almost all of the
planet’s climate zones and habitats.
The emergence of early and modern agriculture
allowed us to grow more food for each unit of land
Death rates dropped sharply because of improved
sanitation and health care.
4. Human Population Growth
Continues But it is Unevenly
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
Geographically, growth is unevenly distributed.
About 1% of the 83 million new arrivals on the planet in 2011 were
added to the world’s more-developed countries
The other 99% were added to the world’s middle- and low-income,
less-developed countries. At least 95% of the 2.6 billion people likely
to be added to the world’s population between 2011 and 2050 will
end up in the least-developed countries.
6. Human Population Growth
Continues but it is Unevenly
Cultural carrying capacity is the maximum number of people who could live in
reasonable freedom and comfort indefinitely, without decreasing the ability of
the earth to sustain future generations.
8. The Human Population Can
Grow, Decline, Or Remain
Birth rate, or crude birth rate, is the number of live
births per 1,000 people in a population in a given
Death rate, or crude death rate, is the number of
deaths per 1,000 people in a population in a given
Population change of an area = (births +
immigration) - (deaths + emigration)
9. Women are Having Fewer Babies
but not Few Enough to Stabilize
the World’s Population
The total fertility rate (TFR) is the average number
of children born to women in a population during
their reproductive years.
Between 1955 and 2011, the average global lifetime
number of births of live babies per woman dropped
from 5 to 2.5.
A TFR of 2.1 will eventually halt the world’s
10. Several Factors Affect Birth Rates
and Fertility Rates
A particular country’s average birth rate and TFR
can be affected by:
The importance of children as a part of the labor
The cost of raising and educating children.
The availability of, or lack of, private and public
11. Several Factors Affect Birth Rates
and Fertility Rates
The educational and employment opportunities
available for women.
The average age at marriage.
The availability of legal abortions.
The availability of reliable birth control methods.
Religious beliefs, traditions, and cultural norms.
12. Migration Affects an Area’s
Migration is the movement of people into
(immigration) and out of (emigration) specific
Most people who migrate from one country to
another are seeking jobs.
Religious persecution, ethnic conflicts, political
oppression, wars, and certain types of
environmental degradation are also factors.
Environmental refugees are people who migrate
due to environmental degradation such as soil
erosion and water and food shortages. One UN
study estimated that a million people are added to
this category every year.
13. How Does a Population’s Age
Structure Affect Its Growth or
14. A Population’s Age Structure
Helps Us to Make Projections
Age structure is the numbers or percentages of males and females in
young, middle, and older age groups in a given population.
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:
Prereproductive (0–14): normally too young to have children.
Reproductive (15–44): normally able to have children.
Postreproductive (45+): normally too old to have children.
15. A Population’s Age Structure
Helps Us to Make Projections
Demographic momentum is rapid population growth in a country that
has a large percentage of people younger than 15, and happens when
a large number of girls enter their prime reproductive years.
1.8 billion people will move into their reproductive years by 2025.
Most future human population growth will take place in less-
developed countries due to their population age structure.
The global population of seniors (age 65 and older) is increasing due
to declining birth rates and medical advances that have extended life
17. There are Three Effective Ways to
Slow Population Growth
The three most effective ways to slow or stop
population growth are:
Elevate the status of women
Encourage family planning and reproductive health
18. Stage 1
a high birth
and a high
Population grows rapidly because
birth rates are high and death
rates drop because of improved
food production and health
levels off and then
declines as birth rates
equal and then fall
below death rates
50 Birth rate
20 Death rate
Low Increasing Very high Decreasing Low Zero Negative
19. Promote Economic Development
As countries become industrialized and
economically developed, their populations tend to
grow more slowly. This demographic transition has
20. Promote Economic Development
Less-developed countries may transition to slower
growth if modern technology can raise per capita
incomes by bringing economic development and
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.
21. Empowering Women Can Slow
Women tend to have fewer children if they are
educated, have the ability to control their own
fertility, hold a paying job outside the home, and
live in societies that do not suppress their rights.
Women account for 66% of all hours worked but
receive only 10% of the world’s income and own
just 2% of the world’s land.
Women make up 70% of the world’s poor and 64%
of its 800 million illiterate adults.
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
22. Promote Family Planning
Family planning provides educational and clinical
services that help couples choose how many
children to have and when to have them.
Successes of family planning:
Without family planning programs that began in
the 1970s, the world’s population would be about
8.5 billion instead of the current 7 billion.
Family planning has reduced the number of
abortions performed each year and decreased the
numbers of mothers and fetuses dying during
23. Promote Family Planning
Problems that have hindered success in some
42% of all pregnancies in less-developed countries
are unplanned and 26% end with abortion.
An estimated 201 million couples in less-developed
countries want to limit their number of children,
but lack access to family planning services.
24. What are the Major Urban
Resource and Environmental
25. Scientists See Three Important
An increasing percentage of the world’s people live in urban areas.
Urban areas grow in two ways—by natural increase due to births and
by immigration, mostly from rural areas.
Three major trends in urban population dynamics have emerged:
The proportion of the global population living in urban areas
increased from 2% in 1850 to 50% today, and is projected to be 70%
26. Scientists See Three Important
The numbers and sizes of urban areas are mushrooming. We now
have cities with 10 million or more people (megacities or
megalopolises) and will soon have hypercities with more than 20
million people. Megacities and hypercities are merging into
megaregions that can stretch across entire countries.
Poverty is becoming increasingly urbanized, mostly in less-
developed countries. An estimated 1 billion people in less-
developed countries live in urban slums and shantytowns.
27. Urban Sprawl Gobbles Up the
Urban sprawl, or the growth of low-density
development on the edges of cities and towns, is
eliminating surrounding agricultural and wild lands.
Urban sprawl is the product of affordable land,
automobiles, relatively cheap gasoline, and poor
28. Urban Sprawl Gobbles Up the
Urban sprawl has caused or contributed to a
number of environmental problems.
People are forced to drive everywhere, resulting in
more emission of greenhouse gases and air
Sprawl has decreased energy efficiency, increased
traffic congestion, and destroyed prime cropland,
forests, and wetlands.
Sprawl has led to the economic deaths of many
central cities as people and businesses move out.
30. Urbanization Has Advantages
Cities are centers of industry, commerce, transportation, innovation,
education, technological advances, and jobs.
Urban residents in many parts of the world tend to live longer than do
rural residents, and have lower infant mortality and fertility rates.
Cities provide better access to medical care, family planning, education,
and social services.
Recycling is more economically feasible.
Concentrating people in cities helps to preserve biodiversity.
Central cities can save energy if residents rely more on energy efficient
mass transportation, walking, and bicycling.
31. Urbanization Has Disadvantages
Most urban areas are unsustainable systems.
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.
Most cities lack vegetation.
Destroyed vegetation could have absorbed air pollutants, given off
oxygen, provided shade, reduced soil erosion, provided wildlife habitats,
and offered aesthetic pleasure.
Many cities have water problems.
Providing water to cities can deprive rural and wild areas of surface
water and can deplete underground water supplies.
32. Urbanization Has Disadvantages
Cities in arid areas that depend on water withdrawn from rivers and
reservoirs behind dams will face increasing problems.
Cities can have flooding problems for several reasons:
Being built on floodplains or near low-lying coastlines.
Covering land with buildings, asphalt, and concrete causes
precipitation to run off quickly and overload storm drains.
33. Urbanization Has Disadvantages
Destroying or degraded large areas of wetlands that have served as
natural sponges to help absorb excess storm water.
Flooding as sea levels rise because of projected climate.
Cities in arid areas that depend on water bodies fed by mountaintop
glaciers will face water shortages if global warming melts the
35. Fig. 6-18, p. 110
Energy Solid wastes
Food Waste heat
Raw materials Greenhouse gases
36. Cities Tend to Concentrate Pollution And Health
Cities produce most of the world’s air pollution,
water pollution, and solid and hazardous wastes.
High population densities can increase the spread
of infectious diseases, especially if adequate
drinking water and sewage systems are not
37. Cities Affect Local Climates
Cities tend to be warmer, rainier, foggier, and
Heat generated by cars, factories, furnaces, lights,
air conditioners, and heat-absorbing dark roofs and
streets creates an urban heat island surrounded by
cooler suburban and rural areas.
The artificial light created by cities affects some
plant and animal species.
38. Life is a Desperate Struggle For
the Urban Poor in Less-Developed
At least 1 billion people live under crowded and
unsanitary conditions in cities in less-developed
Slums are areas dominated by tenements and
rooming houses where several people might live in
a single room.
Squatter settlements and shantytowns are on the
outskirts of cities, and usually lack clean water
supplies, sewers, electricity, and roads, and are
subject to severe air and water pollution and
hazardous wastes from nearby factories.
40. Motor Vehicles Have Advantages And
They provide mobility and offer convenient and
They can be symbols of power, sex appeal, social
status, and success.
Much of the world’s economy is built on producing
motor vehicles and supplying fuel, roads, services,
and repairs for them.
Globally, automobile accidents kill approximately
1.2 million people a year and injure another 15
41. Reducing Automobile Use is not Easy, But
it Can Be Done
Raise parking fees and charge tolls on roads, tunnels, and bridges
leading into cities, especially during peak traffic times.
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.
42. Some Cities Promote Alternatives To
The following are alternatives to cars, each with its
own advantages and disadvantages:
Mass-transit rail systems in urban areas
Bus systems in urban areas
High-speed rail systems between urban areas
44. We Can Make Urban Areas More
Environmentally Sustainable and
Enjoyable Places To Live
Smart growth encourages environmentally
sustainable development requiring less
dependence on cars, controls and directs sprawl,
and reduces wasteful resource use, by using zoning
laws and other tools to channel growth into areas
where it can cause less harm.
New urbanism involves less-developed villages
within cities, so that people can live within walking
distance of where the work, shop, and go for
45. Three Big Ideas
The human population is increasing rapidly and may soon bump up
against environmental limits.
We can slow human population growth by reducing poverty,
encouraging family planning, and elevating the status of women.
Most urban areas are unsustainable, but they can be made more
sustainable and livable within your lifetime.
Figure 6.2: This graph tracks the annual growth rate of world population, 1950–2010, with projections to 2050. (Data from United Nations Population Division and U.S. Census Bureau)
Figure 6.11: The demographic transition, which a country can experience as it becomes industrialized and more economically developed, can take place in four stages. See an animation based on this figure at CengageNOW. Question: At what stage is the country where you live?
Figure 6.8 natural capital degradation: Urban areas are rarely sustainable systems. The typical city depends on large nonurban areas for huge inputs of matter and energy resources, while it generates large outputs of waste matter and heat. Question: How would you apply the three principles of sustainability (see back cover) to lessen some of these impacts?