1. Sprawled City
Lesson 5
THE HUMAN POPULATION AND URBANIZATION
1

2. How Many People Can the Earth
Support?
2

3. Human Population Growth
Continues But it is Unevenly
Distributed
 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:
 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
area farmed.
 Death rates dropped sharply because of improved
sanitation and health care.
3

4. Human Population Growth
Continues But it is Unevenly
Distributed
 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.
 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.
4

5. 2.5
2.0
1.5
1.0
0.5
Average
annual
global
growth
rate
(percent)
0.0
1970 1990 2010 2030 2050
Year
1950
5

6. Human Population Growth
Continues but it is Unevenly
Distributed
 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.
6

7. What Factors Influence the Size of
the Human Population?
7

8. The Human Population Can
Grow, Decline, Or Remain
Fairly Stable
 Birth rate, or crude birth rate, is the number of live
births per 1,000 people in a population in a given
year.
 Death rate, or crude death rate, is the number of
deaths per 1,000 people in a population in a given
year.
 Population change of an area = (births +
immigration) - (deaths + emigration)
8

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
population growth.
9

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
force.
 The cost of raising and educating children.
 The availability of, or lack of, private and public
pension systems.
 Urbanization.
10

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.
11

12. Migration Affects an Area’s
Population Size
 Migration is the movement of people into
(immigration) and out of (emigration) specific
geographic areas.
 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.
12

13. How Does a Population’s Age
Structure Affect Its Growth or
Decline?
13

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.
14

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
spans.
15

16. How Can We Slow Human
Population Growth?
16

17. There are Three Effective Ways to
Slow Population Growth
 The three most effective ways to slow or stop
population growth are:
 Reduce poverty
 Elevate the status of women
 Encourage family planning and reproductive health
care.
17

18. Stage 1
Preindustrial
Stage 2
Transitional
Stage 3
Industrial
Stage 4
Postindustrial
Population
grows very
slowly
because of
a high birth
rate (to
compensate
for high
infant
mortality)
and a high
death rate
Population grows rapidly because
birth rates are high and death
rates drop because of improved
food production and health
Population
growth
slows as
both birth
and death
rates drop
because of
improved
Population growth
levels off and then
declines as birth rates
equal and then fall
below death rates
80
70
60
Total population
50 Birth rate
40
30
20 Death rate
Birth
rate
and
death
rate
(number
per
1,000
per
year)
10
0
Low Increasing Very high Decreasing Low Zero Negative
Growth rate
over time
food
production,
health, and
education
18

19. Promote Economic Development
 As countries become industrialized and
economically developed, their populations tend to
grow more slowly. This demographic transition has
four phases:
 Preindustrial
 Transitional
 Industrial
 Postindustrial
19

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
family planning.
 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.
20

21. Empowering Women Can Slow
Population Growth
 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
read.
21

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
pregnancy.
22

23. Promote Family Planning
 Problems that have hindered success in some
countries:
 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.
23

24. What are the Major Urban
Resource and Environmental
Problems?
24

25. Scientists See Three Important
Urban Trends
 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%
by 2050.
25

26. Scientists See Three Important
Urban Trends
 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.
26

27. Urban Sprawl Gobbles Up the
Countryside
 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
urban planning.
27

28. Urban Sprawl Gobbles Up the
Countryside
 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
pollution.
 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.
28

29. Urban Sprawl
29

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.
30

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.
31

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.
32

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
glaciers.
33

34. Urban Areas are Rarely Sustainable Systems
34

35. Fig. 6-18, p. 110
Inputs Outputs
Energy Solid wastes
Food Waste heat
Water pollutants
Water
Air pollutants
Raw materials Greenhouse gases
Money Wealth
Noise
Manufactured
goods
Manufactured
goods
Information Ideas
35

36. Cities Tend to Concentrate Pollution And Health
Problems
 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
available.
36

37. Cities Affect Local Climates
 Cities tend to be warmer, rainier, foggier, and
cloudier.
 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.
37

38. Life is a Desperate Struggle For
the Urban Poor in Less-Developed
Countries
 At least 1 billion people live under crowded and
unsanitary conditions in cities in less-developed
countries.
 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.
38

39. How Does Transportation Affect
Urban Environmental Impacts?
39

40. Motor Vehicles Have Advantages And
Disadvantages
 They provide mobility and offer convenient and
comfortable transportation.
 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
million people.
40

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.
41

42. Some Cities Promote Alternatives To
Cars
 The following are alternatives to cars, each with its
own advantages and disadvantages:
 Bicycles
 Mass-transit rail systems in urban areas
 Bus systems in urban areas
 High-speed rail systems between urban areas
(bullet trains)
42

43. How Can Cities Become More
Sustainable and Livable?
43

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
entertainment
44

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.
45

46. Thank You!
46