1. The Human Population and Urbanization

2. How Many people can the earth support?

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. Total fertility rates for the US between 1917-2011

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

15. 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

16. 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

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.

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 Age structure can influence population growth rates.
Figure 7.9

23. 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.
The global population of seniors (age 65 and older) is increasing due to declining birth rates and medical advances that have extended life spans.

24. Generalized population age-structure diagrams

25. 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.

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

27. 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.

28. 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

29. How can we slow human population growth?

30. 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.

31. 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

32. The demographic transition

33. 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

34. 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.

35. 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.

36. 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

37. 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.

38. What are the major urban resource and environmental problems?

39. 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.

40. Scientists see three important urban trends
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.

41. 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) and will soon have hypercities with more than 20 million people.
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.

42. 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

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 by reducing 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, commerce, transportation, innovation, education, technological advances, and jobs.
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.

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
Destroyed vegetation could have absorbed air pollutants, given off oxygen, provided shade, reduced soil erosion, or provided 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. Inputs Outputs Energy Solid wastes Waste heat Food Air pollutants
Water
Water pollutants
Raw materials
Greenhouse gases
Manufactured
goods
Manufactured goods
Noise
Money
Wealth
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?
Information
Ideas
Fig. 6-18, p. 110

57. 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.

58. 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.

59. How does transportation affect urban environmental impacts?

60. Cities can grow outward or upward
Most people living in compact cities get around by walking, biking, or using mass transit such as rail or buses.
In countries such as the United States, Canada and Australia, plentiful land and networks of highways have produced dispersed cities whose residents depend on motor vehicles for most travel.

61. Cities can grow outward or upward
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.

62. 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.

63. Motor vehicles have advantages and disadvantages
Motor vehicles are the one of the world’s largest sources of outdoor air pollution.
They are the fastest-growing source of climate-changing CO2 emissions.
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

64. Reducing automobile use is not easy, but it can be done
A user-pays approach makes drivers pay for most of the environmental and health costs caused by automobile use
An example is a tax on gasoline that covers the estimated harmful costs of driving
Gasoline revenues could be used to help finance alternatives to cars
Taxing gasoline heavily would be difficult in the U.S. for several reasons.
Strong opposition from the public, and from transportation-related industries.
The dispersed nature of most U.S. urban areas.
Lack of fast, efficient, reliable, affordable mass transit options.

65. 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)

66. Alternatives to cars

67. How can cities become more sustainable and livable?

68. 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
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

69. Smart growth tools

70. CASE STUDY: The new urban village of Vauban
Vauban is a suburb outside the city of Freiberg, Germany that is virtually free of cars.
Street parking, driveways, and garages are generally forbidden in the village. A parking space in a city garage costs $40,000.
Homes are within easy walking distance of trains, stores, banks, restaurants, and schools. There are numerous bike paths and a car-sharing club. Mass transit allows residents to work or shop in the city of Freiburg.
There are no single-family homes, only energy-efficient row houses that use passive solar energy.

71. CASE STUDY: The new urban village of Vauban
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.
Build and redesign cities for people, not cars.
Reduce the waste of matter and energy.
Prevent pollution.
Reuse, recycle, and compost 60–85% of all municipal solid waste.
Protect and encourage biodiversity by preserving undeveloped land and protecting and restoring natural systems and wetlands in and around cities.
Promote urban gardens and farmers markets.
Use zoning and other tools to keep urban sprawl at environmentally sustainable levels.

72. 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.