Environmentalists and economists increasingly agree that efforts to protect the environment and to achieve better living standards can be closely linked and are mutually reinforcing. Slowing the increase in population, especially in the face of rising per capita demand for natural resources, can take pressure off the environment and buy time to improve living standards on a sustainable basis (92, 196, 245, 254).

Although it is not clear whether in the long run rapid population growth causes poverty, "it is clear that high fertility leading to rapidly growing population will increase the number of people in poverty in the short run and, in some cases, make escape from poverty more difficult," observes researcher Dennis A. Ahlburg (7). It is difficult to make investments for the future when resources are already fully used trying to keep up with the current needs of rapidly growing populations.

As population growth slows, countries can invest more in education, health care, job creation, and other improvements that help boost living standards (245). In turn, as individual income, savings, and investment rise, more resources become available that can boost productivity. This dynamic process has been identified as one of the key reasons that the economies of many Asian countries grew rapidly between 1960 and 1990 (144).

In recent years fertility has been falling in many developing countries and, as a result, annual world population growth has fallen to about 1.4% in 2000 compared with about 2% in 1960. The UN estimated recently that population is growing by about 78 million per year, down from about 90 million estimated early in the 1990s (243). Still, at the current pace world population increases by about 1 billion every 13 years. World population surpassed 6 billion in 1999 and is projected to rise to over 8 billion by 2025.

Globally, fertility has fallen by half since the 1960s, to about three children per woman (243). In 65 countries, including 9 in the developing world, fertility rates have fallen below replacement level of about two children per woman (224). Nonetheless, fertility is above replacement level in 123 countries, and in some countries it is substantially above replacement level. In these countries the population continues to increase rapidly.

About 1.7 billion people live in 47 countries where the fertility rate averages between three and five children per woman. Another 730 million people live in 44 countries where the average woman has five children or more (182).

Almost all population growth is in the developing world. As a result of differences in population growth, Europe's population will decline from 13% to 7% of world population over the next quarter century, while that of sub-Saharan Africa will rise from 10% to 17%. The shares of other regions are projected to remain about the same as today (169).

As population and demand for natural resources continue to grow, environmental limits will become increasingly apparent (169). Water shortages are expected to affect nearly 3 billion people in 2025, with sub-Saharan Africa worst affected (82). Many countries could avoid environmental crises if they took steps now to conserve and manage supplies and demand better, while slowing population growth by providing families and individuals with information and services needed to make informed choices about reproductive health.

Family planning programs play a key role. When family planning information and services are widely available and accessible, couples are better able to achieve their fertility desires (133). "Even in adverse circumstance—low incomes, limited education, and few opportunities for women—family planning programs have meant slower population growth and improved family welfare," the World Bank has noted (27).

If every country made a commitment to population stabilization and resource conservation, the world would be better able to meet the challenges of sustainable development. Practicing sustainable development requires a combination of wise public investment, effective natural resource management, cleaner agricultural and industrial technologies, less pollution, and slower population growth.

Better resource management protects the environment and preserves nature's productive capacity. Stronger economies can afford to invest more in protecting the environment. Slower population growth can speed economic growth and conserve natural resources.