Chapter Summary

Human populations must achieve a working relationship with their environment. Sociologists have applied theories of ecology to the study of human communities, including use of the concept of ecosystem, with populations as their unit of study.

Population Demography is the science dealing with the size, distribution, composition, and changes in population.

• Elements in Population Change.  
  All population change within a society can be reduced to three factors: the birth rate, the death rate, and the migration rate into or out of the society. Demographers look at crude birth rate, general fertility rate, age-specific fertility, fecundity, zero population growth, crude death rate, age-specific death rates, and infant mortality rate. Migration affects population, and demographers measure the net migration rate. Movement may take the form of international migration or internal migration. Births, deaths, and migration affect the growth rate.

• Population Composition.  
  Sociologists are also interested in the composition of a population, particularly in the sex ratio and age composition. A population pyramid is a useful tool for analyzing population change and discerning population trends.

• Malthus and Marx: Two Views of Population Growth.  
  Thomas Malthus held that population increases more quickly than food supply. Karl Marx insisted that an excess of population is related to the availability of employment opportunities, not to a fixed supply of food. Neo-Malthusians are those who agree with many of Malthus’s ideas but who favor contraception for population control.

• Demographic Transition.
  Demographic transition theory holds that the process of modernization is associated with three stages in population change: high potential growth, transitional growth, and population stability.

• Population Policies.  
  Fertility reduction policies are based on family planning, a developmentalist strategy, or a societalist perspective.

• The Effects of Crowding.  
  Population buildup has bad effects on deer, rats, and a variety of other organisms; the impact of crowding on human behavior is more complex and does not invariably result in pathology. Social scientists distinguish between density and crowding.

The city is one of the most striking features of our modern era, basic to many of the characteristics of modern society.

• The Origin and Evolution of Cities.  
  Preindustrial cities were primarily small affairs. Urbanization has proceeded rapidly during the past 180 years, resulting in industrial-urban centers, metropolitan cities, megalopolises, and global cities.

• Patterns of City Growth.  
  Sociologists provide a number of models of city growth: the concentric circle model, the sector model, and the multiple nuclei model.

• Ecological Processes: Segregation and Gentrification.  
  The structural patterning of cities derives from a number of underlying ecological processes. One process by which natural areas are formed is segregation. Invasion and succession are also critical ecological processes. Urban gentrification is the return of middle-class professionals to older urban neighborhoods.

• Urban Crisis: Cities in Decline.
  Urban decline in many American cities has been both descriptive and functional.

• Sprawling Urban Growth: The Rise of "Edge" Cities.  
  "Outer cities,""minicities," or "edge cities" have been made possible by beltways and expressways, and the development of a service-based economy in which telecommunications allow service-sector firms to locate anywhere.

Humans have transformed one-third to one-half of the earth’s land surface and use more than half of all the world’s accessible surface fresh water; some 25 percent of the world’s bird species have been driven to extinction, and forested areas have decreased by a third since the rise of agriculture.

• Human-Environment Interactions: A Closer Look.  
  Sociologists are interested in the relationships between population size, politics and economics, environment, and technology. While humans can overexploit natural resources, they can also protect and restore them.

• The Functionalist Perspective.
  Functionalist theorists see the ecosystem as exhibiting a tendency toward equilibrium in which its components maintain a delicately balanced relationship.

• The Conflict Perspective.  
  Some conflict theorists say that the basic issue is not one of how much is available but which individuals and groups will secure a disproportionate share of what is available.

• The Interactionist Perspective.
  Symbolic interactionists focus on "people behaviors" related to environmental issues. Interests include the gap between people’s attitudes and actions and the difference between public and expert perceptions of risk.

• Entering the New Millennium.
  In 1997, Jane Lubchenko, the president of the American Association for the Advancement of Science, called upon scientists to look at the environment as the most important issue of the future. Economist Julian Simon, in contrast, felt that the free market will result in life improving indefinitely. Others see that we have made progress in solving some environmental problems and could continue to do so. Historical analysis shows that the earth’s human inhabitants have changed their view of nature as a usable resource to nature as a life-sustaining global ecosystem.