Fertile ground for uncertainty.

• Position: World Population

Growth in human population continues to abound despite falling fertility rates, and where it heads in the future will continue to confound demographers, states a report from the Worldwatch Institute, Washington, D.C. With the number of women of childbearing age growing and future fertility trends unpredictable, closing the "gender gap"--the difference between women's health, economic, educational, and political status relative to men--may be one key to slowing population growth.

Challenging assertions that world population is "expected" to be slightly higher than 9,000,000,000 people by 2050, up from today's 6,700,000,000, is Robert Engleman, vice president for programs and author of More: Population, Nature, and What Women Want. Demographers with the United Nations and other agencies produce a range of population projections, since there is no certainty about future fertility rates or life expectancies. The projections, which range from less than 8,000,000,000 to nearly 11,000,000,000 people worldwide by mid century, all assume continued declines in childbearing, which are not guaranteed to materialize.

[ILLUSTRATION OMITTED]

"Sustaining further declines in childbearing and increases in life expectancy will require continued efforts by governments to improve access to good health care, and both trends could be threatened by environmental or social deterioration in future decades;' Engleman maintains. "The uncertain future of these factors make...