Demographic transition. Demographic experts believe that the shift from high to low birth rates, and from low to high life expectancy, is brought about by “social modernization.” This complex of changes involves improved health care and access to family planning; higher educational attainment, especially among women; economic growth and rising per capita income levels; and urbanization and growing employment opportunities. Stabilization of the world’s population will therefore depend on continuing or accelerating socioeconomic development in the great majority of the world’s developing countries. A number of factors could impede the demographic transition, including stagnating economic growth, persistent poverty, or cultural factors that encourage large family size despite rising prosperity. If the transition is stalled, global population would presumably continue to rise throughout the next century.
Population projections carried out recently by another institution, Austria’s International Institute for Applied Systems Analysis (IIASA), explicitly address some of the uncertainties underlying population forecasts. IIASA’s projections make use of a probability model, reflecting expert opinion on the future courses of fertility, mortality, and migration, and the extent of their uncertainty. This model leads to a somewhat broader range of estimates than those from the U.N.; according to IIASA, world population in 2050 will probably number between 8.1 billion and almost 12 billion [11].
What are the implications of an approximately doubled world population? Population growth is of most concern where countries appear least able to deal with its consequences. Key issues in providing for increased populations will include the achievement of adequate income levels, food security, employment, and the provision of basic social services. Also critical is the sound management of natural resources that, in many developing countries, still directly support the livelihoods of a majority of their inhabitants. These and other issues are discussed throughout this section.
A significant number of the world’s people already face critical shortfalls of the essentials needed for a healthy life. Some 1.3 billion live in absolute poverty, 840 million are undernourished [12], roughly 1.4 billion lack safe drinking water [13], and about 900 million are illiterate [14]. In many areas, population growth is accelerating the rate of degradation of forests, fisheries, and productive soils. (See Resources at Risk.) Populations at direct risk from environmental degradation are concentrated in the least developed countries of sub-Saharan Africa and south Asia, and in parts of Latin America. Population growth, together with continued economic expansion, also presents risks at the global level. If the world’s population approximately doubles and average incomes continue to rise, it is likely that the production and consumption patterns characteristic of middle- and upper-income social groups will be adopted more widely throughout the developing world. The environmental impacts of the economic activity required to support modern consumer societies are already immense. (See Production and Consumption.) If tomorrow’s consumers use and waste resources in the same manner as today’s, the consequences in terms of global climate change, loss of vital renewable resources, and toxic pollution will be severe.
References and notes
11. Wolfgang Lutz, Warren Sanderson, and Sergei Scherbov, Probability World Population Projections Based on Expert Opinion, Working Paper (WP-96-17) (International Institute for Applied Systems Analysis, Laxenburg, Austria, 1996), p. 20.
12. United Nations Development Program (UNDP), Human Development Report 1997 (Oxford University Press, New York, 1997), pp. 3-4.
13. United Nations Children’s Fund (UNICEF), The Progress of Nations 1997 (UNICEF, New York, 1997).
14. United Nations Educational, Scientific and Cultural Organization (UNESCO), Statistical Yearbook 1996 (UNESCO, Paris, 1996), Table 2.2, p. 2-9.
