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The Human Population and Urbanization

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Presentation on theme: "The Human Population and Urbanization"— Presentation transcript:

1 The Human Population and Urbanization

2 How Many people can the earth support?

3

4 Demography Demography = the application of population ecology to the study of humans Demographers study population size Density and distribution Age structure and sex ratio And birth, death, immigration, and emigration rates

5 Human population growth continues but it is unevenly distributed
For most of history, the human population grew slowly Starting growing exponentially about 200 years ago 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 modern agriculture Death rates dropped because of improved sanitation and health care

6 The human population is still growing rapidly
It took almost all of human history to reach 1 billion In 1930, 130 years later, we reached 2 billion

7 Is population growth really a problem?
Some say NO: People can find or manufacture additional resources to keep pace with population growth. Nations become stronger as their populations grow. Some say YES: Not all resources can be replaced. Even if they could, quality of life suffers. Nations do not become stronger as their populations grow.

8 Human population growth continues but it is unevenly distributed
The rate of population growth has slowed 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 new arrivals on the planet are added to the world’s more-developed countries The other 99% were added to the world’s middle- and low-income, less-developed countries.

9 Annual growth of world population, 1950-2011

10 What factors influence the size of the human population?

11 The human population can grow, decline, or remain fairly stable
Factors that increase population size Birth rate Immigration Factors that decrease population size Death rate Emigration Population change of an area (births + immigration) - (deaths + emigration)

12 Women are having fewer babies but not few enough to stabilize the world’s population
Total fertility rate (TFR) = the average number of children born per female Between 1955 and 2011, the global TFR dropped from 5 to 2.5 Why?

13 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. Urbanization

14 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

15 Total fertility rates for the US between 1917-2011

16 Some major changes took place in the US between 1900-2000

17 Several factors affect death rates
Death rates have significantly dropped in the last century Increased food supplies Better nutrition Medical advances Improved sanitation Safer water supplies Two useful indicators of the overall health of people in a country or region are life expectancy and infant mortality rate Between 1900 and 2011, the average life expectancy in the United States increased from 47 years to 78 years.

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19 Migration affects an area’s population size
Migration is the movement of people into (immigration) and out of (emigration) specific geographic areas. Religious persecution, ethnic conflicts, political oppression, wars, and certain types of environmental degradation can be factors. Environmental refugees are people who migrate due to environmental degradation such as water and food shortages. One UN study estimated that a million people are added to this category every year.

20 How does a population’s age structure affect its growth or decline?

21 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 Population age-structure diagrams are made by plotting the percentages or numbers of males and females 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.

22 Age structure affects future population size
Age pyramid of the U.S. in 2005

23 Age structure Age structure can influence population growth rates.
Figure 7.9

24 A population’s age structure helps us to make projections
Most future human population growth will take place in less-developed countries due to their population age structure. Why? The global population of seniors (age 65 and older) is increasing Declining birth rates Medical advances that have extended life spans.

25 Generalized population age-structure diagrams

26 The American Baby Boom Added 79 million people to the U.S. population 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. As the baby boomers turn 65, the number of seniors will grow sharply through This process has been called the graying of America.

27 The baby-boom generation in the US, 1955, 1985, and 2035

28 Populations made up mostly of older people can decline rapidly
Japan has the world’s highest % of elderly people and the world’s lowest % of young people. Due to its discouragement of immigration, it may face a bleak economic future. 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, limited funds for supporting continued economic development, and fewer children and grandchildren to care for the growing number of elderly people.

29 Some Problems with Rapid Population Decline
Can threaten economic growth Labor shortages Less government revenues with fewer workers Less entrepreneurship and new business formation Less likelihood for new technology development Figure 6.9: Rapid population decline can cause several problems. Question: Which three of these problems do you think are the most important? Increasing public deficits to fund higher pension and health-care costs Pensions may be cut and retirement age increased Fig. 6-9, p. 103

30 How can we slow human population growth?

31 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.

32 The demographic transition
Demographic transition = a model of economic and cultural change to explain the declining death and birth rates in industrializing nations Stable preindustrial state of high birth and death rates change to a stable post-industrial state of low birth and death rates As mortality decreases, there is less need for large families Parents invest in quality of life

33 The demographic transition

34 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

35 Demographic transition: Stages
Pre-industrial stage: high death rates and high birth rates Transitional stage: death rates fall due to rising food production and better medical care. Birth rates remain high, so population surges. Industrial stage: birth rates fall, as women are employed and as children become less economically useful in an urban setting. Population growth rate declines. Post-industrial stage: birth and death rates remain low and stable; society enjoys fruits of industrialization without threat of runaway population growth.

36 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 live in societies that do not suppress their rights. 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.

37 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

38 Promote family planning
Problems that have hindered success in some countries: 42% of all pregnancies in less-developed countries are unplanned Couples in less-developed countries want to limit their number of children, but lack access to family planning services.

39 What are the major urban resource and environmental problems?

40 Scientists see three important urban trends
An increasing percentage of the world’s people live in urban areas. Urban areas grow in two ways natural increase due to births Immigration

41 Scientists see three important urban trends
Three major trends in urban population dynamics have emerged: 1. The proportion of the global population living in urban areas has greatly increased 2% in 1850 to 50% today, and is projected to be 70% by 2050

42 Scientists see three important urban trends
2. The numbers and sizes of urban areas are mushrooming We now have cities with 10 million or more people (megacities) and will soon have hypercities with more than 20 million people. 3. 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.

43 Major urban areas throughout the world – city lights at night

44 Urbanization in the United States
Between , the % of the U.S. population living in urban areas increased from 5% to 79%. This population shift has occurred in four phases. People migrated from rural areas to large central cities. Many people migrated from large central cities to smaller cities and suburbs. Many people migrated from the North and East to the South and West. Some people fled cities and moved to developed areas outside of suburbs.

45 Urbanization in the United States
There are upsides to urbanization Conditions in U.S. cities have improved with better working and housing conditions Concentrating people in urban areas has helped protect the country’s biodiversity Reduced the destruction and degradation of wildlife habitat

46 Urban areas in the US with more than 1 million people

47 Urban sprawl gobbles up the countryside
Growth of low-density development on the edges of cities and towns Eliminates surrounding agricultural and wild lands Urban sprawl is the product of affordable land, automobiles, relatively cheap gasoline, and poor urban planning

48 Urban sprawl in and around Las Vegas, NV, 1973 and 2009

49 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 Decreased energy efficiency, increased traffic congestion, and destroyed prime cropland, forests, and wetlands

50 Urban sprawl

51 Urbanization has advantages
Cities are centers of industry 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

52 Urbanization has disadvantages
Most urban areas are unsustainable systems Depend on 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 Vegetation could absorb air pollutants, give off oxygen, provided shade, reduce soil erosion, or provide wildlife habitats Many cities have water problems Providing water to cities can deprive rural and wild areas of surface water and can deplete underground water supplies

53 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

54 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.

55 Urban areas are rarely sustainable systems

56 Cities tend to concentrate pollution and health problems
Cities produce most of the world’s air pollution water pollution 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.

57 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 The artificial light created by cities affects some plant and animal species.

58 How can cities become more sustainable and livable?

59 Population growth affects the environment
The IPAT model: I = P x A x T x S Our total impact (I) on the environment results from the interaction of population (P), affluence (A) and technology (T), with an added sensitivity (S) factor Population = individuals need space and resources Affluence = greater per capita resource use Technology = increased exploitation of resources Sensitivity = how sensitive an area is to human pressure Further model refinements include education, laws, ethics

60 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 Reduces wasteful resource use Uses zoning laws and other tools to channel growth into areas where it can cause less harm

61 Smart growth tools

62 Ecocities An ecocity emphasizes the following goals:
Use solar and other locally available, renewable energy resources and design buildings to be heated and cooled as much as possible by nature Reduce the waste of matter and energy Prevent pollution Protect and encourage biodiversity Promote urban gardens and farmers markets Use zoning and other tools to keep urban sprawl at environmentally sustainable levels


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