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The unprecedented population growth that occurred in the last century and the projected growth in the next will put increasing pressure on the natural environment and threaten the health of the Earth's basic ecosystems. This Population Bulletin examines the likely global impacts of population growth and distribution on food supply, energy consumption, emission of greenhouse gases, forests, oceans, and other environmental factors. The authors review various models developed to explore the complex relationship among population change, consumption levels, resources, and environmental health, and they discuss the various philosophical perspectives that affect the interpretation of model results.

Demographic factors such as uneven regional population distribution and growth and migration from rural to urban areas are analyzed in the context of resource use. The authors also look at the interaction of such social factors as poverty, affluence, and consumption patterns with demographic trends and environmental impact. About 90 percent of population growth is occurring in low-income regions such as sub-Saharan Africa and South Asia, where water supplies and basic health systems are deficient. By 1994, for example, about 1.2 billion people in developing countries still lacked safe water supplies and about 3 billion-more than half the world's population-lacked access to sanitation services. These countries also lack the resources or institutional capacity to invest in sound environmental policies or to reduce the environmental impact of their economic growth.

Population growth in rapidly expanding economies in Asia and other areas is accelerating the emission of greenhouse gases that can change the Earth's climate. Populations in industrialized countries are expanding slowly but are major contributors to environmental pressures through their historically high levels of material consumption and energy use.

This Population Bulletin also discusses steps already taken by the international community to combat environmental problems and policies most likely to ensure a healthy environment and an abundance of resources in the face of massive population growth and the environmental problems that accompany it.