SOMEWHERE in the world, a woman gives birth every third of a second. "We've got to find that woman and stop her," goes the old joke, but population growth is no laughing matter. The numbers add up to about a quarter million a day and nearly 95 million per year.For years, experts have argued over whether this constitutes a "population explosion." For certain, it means the number of human beings on Earth will grow from 5.4 billion today to more than 11 billion towards the end of the next century, even if birthrates continue to taper off. And the total could top 14 billion if growth rates remain higher than projected. What's becoming increasingly clear as well is the environmental impact of population growth. A recent report by the United Nations Population Fund cites some of the problems: loss of 70,000 square kilometers (roughly 27,000 square miles) of farmland each year because of worn-out soil; destruction of 11 million hectares (27.5 million acres) of tropical forests and another 10 million hectares "grossly degraded" from fuel-wood harvesting, grazing, and subsistence cultivation; groundwater depletion and surfa ce-water pollution; loss of tens of thousands of species annually. Those of us in the developed world tend to tsk-tsk over high rates of population increase in Africa and South Asia. If they just got themselves down to two or three kids per couple like us, wouldn't that take care of the problem? Yes, if we in the Western world weren't gobbling up natural resources so fast ourselves. "With barely 25 percent of the world's population, developed countries consume 75 percent of all energy used, 79 percent of all commercial fuels, 85 percent of all wood products, and 72 percent of all steel production," states the UN report. "In addition, developed countries generate nearly three quarters of all carbon dioxide emissions which account for half of the greenhouse gases in the atmosphere." Stanford University population experts Paul and Anne Ehrlich have worked out a formula for this. It's I = P x A x T where the impact of a group or nation on the environment equals population times affluence (consumption) times the damage caused by the technology used to supply that affluence. It's not just loss of other species due to habitat destruction and pollution that is the outcome of population growth. There now are estimated to be 10 million "environmental refugees" in the world - a growing number that is higher than all the refugees after World War II. The UN Children's Fund last year reported that 14 million children die each year because of environmental degradation, including lack of clean water and sufficient nourishment. The Worldwatch Institute reports that the increase in worl d grain production is only half the population increase, which means that the hunger problem in developing countries is getting worse. "Not just the environment is at risk," says Susan Weber, executive director of Zero Population Growth. "Unabated population growth will undermine virtually every effort to ensure a quality future - from economic development to peace, from health and education investments to the rights of women and minorities." At the point where environment and population coincide, women are taking the lead in searching for solutions. It was a panel of women from environmental and population organizations that released the recent UN report. Population will be a key topic when a thousand women meet in Miami this week for the "World Women's Congress for a Healthy Planet," which is being sponsored by the Women's Environment & Development Organization. Village women in Nepal and India have promoted family planning efforts that hav e brought down birthrates. The two key needs are money and a change in attitude. For just $16 a couple, family-planning information and contraception can be provided to millions. Important will be enlightenment of men: those who see their virility in terms of offspring, those who dominate patriarchal religions, and those who run the Western governments that have hesitated to fund population programs to the extent needed. It's in everyone's interest to see that the resources are provided, the attitudes changed.