WASHINGTON -- Women in many poor, developing countries are having fewer children than their mothers did, an international survey showed recently.
This drop in fertility rates is a welcome trend on a planet whose population will double during the next century, said experts attending the Demographic and Health Surveys World Conference.
But it will not prevent changes in the lifestyles of virtually everyone on earth as the world's population goes from an expected 6 billion in 1998 to 12 billion near the end of the next century, said Martin Vsessen of the Institute for Resource Development.
"The sobering fact" is that "no matter what we do, the world population will double," said Duff Gillespie of the U.S. Agency for International Development Office of Population.
The explosive growth rate may be slowing, though. Survey results released at the conference showed that the fertility rate -- average births per woman -- in the developing world fell from 6.1 in the late 1960s to 4.2 in the late 1980s.
The survey results were cited as the first evidence of a fertility decline in sub-Saharan Africa -- the global region with the fastest population growth rates.
The fertility rates in the developing countries are still far above those in the industrialized world. The rate in the United States, for instance, is 1.9, said Kristin Jones of the Institute for Resource Development, which conducted the survey of 29 developing countries for AID.
A global fertility rate of 2.1 births per woman is enough to keep the earth's population stable.
In many Third World countries, the declining fertility rate reflects "a revolutionary change in the way couples and government are looking at population control," Mr. Gillespie said.
In Africa, couples have traditionally wanted many children to help them farm and to provide security for their old age, said Olikoye Ransome-Kuti, Nigeria's minister of health. High death rates among children also encouraged women to have many offspring to ensure the survival of at least a few, he said.
Reduced infant mortality, increased availability of contraceptives and changing cultural attitudes have all combined to reduce Nigeria's fertility rate, said Mr. Ransome-Kuti, who delivered the opening address of the World Conference.
In the surveyed countries, the fertility rates ranged from 7.6 children per woman in the African nation of Mali and 7.5 in Uganda to 2.2 in Thailand in Southeast Asia and 2.9 in Colombia in Central America.
As much as 97 percent of global population growth between now and 2020 will take place in Africa, Asia and Latin America -- in countries least able to absorb more people, the demographers warned. One reason that the doubling of world population is inevitable is that more than half the population of the developing world will be below the age of 25 by 2000. As these young people form families -- even small families -- population growth will accelerate.
"The world probably can support a doubling of the population," Mr. Vsessen said, "but it will be a world that is very different." The crowded conditions of cities such as Singapore will be commonplace around the world, he predicted. And methods will have to be developed to get food more efficiently from areas of surplus to areas of famine.
The demographers said there is no single solution to reducing birth rates in developing countries. Governments must realize that rapid population growth destabilizes their economies. Contraceptives must be made available and couples educated in family planning. Cultures must accept small families as desirable.