The U.N.'s high projection, by contrast, shows the population passing 28 billion in 2150 and continuing to climb afterwards. As biologists, we find this projection utterly unrealistic. It makes no allowance for rising death rates due to problems connected with rapid population growth, including the need to supply food to ever-more people; the appearance of novel viruses and resistant strains of old microbial enemies; and general environmental deterioration. To our minds, a likelier outcome would be population limitation resulting from some combination of plague, famine, or war.
The U.N.'s low projection is considerably more interesting. It shows the world population peaking at about 8 billion around 2050 and thereafter slowly declining, dropping below 5 billion by 2150. This assumes that fertility can soon be reduced globally to below replacement level. (Replacement level is when couples just replace themselves in the next generation--at today's mortality rates that means an average of slightly more than two children per family--leading eventually to zero population growth.)
We believe the world can attain below replacement level fertility with a concerted international effort. After all, the industrialized world's average fertility is already well below replacement, and China's is not far behind. If average fertility elsewhere in the developing world could be reduced by half by about 2015, the population surely could be held well below the U.N.'s best-guess 11.2 billion peak.
WEALTH DOESN'T ALWAYS MEAN SMALLER FAMILIES
But how should a concerted international effort be framed? The answer isn't simple because the factors that determine fertility rates are extremely complex and sometimes contradictory, and they vary from culture to culture.
Several decades ago, experts had little understanding of what motivates people to have smaller families, although most agreed that a major prerequisite was ensuring that more infants survived to adulthood. They also thought that, once children were no longer income-producers, but instead cost money to feed, clothe, and educate, couples would find smaller families advantageous. But experts disagreed about the value of programs specifically oriented toward birth control. Some development specialists believed such programs were unnecessary because people would naturally desire smaller families in the wake of modernization and industrialization--in short, development itself would be the best contraceptive.
Nonetheless, family planning programs were established in many developing countries, and by the mid-1970s several showed striking success (among them: Taiwan, South Korea, Singapore, Hong Kong, Sri Lanka, Costa Rica, Trinidad, Tobago, and Barbados). By 1980, the most remarkable turnaround was in China, where an indigenous program had cut the average family size by half in only 10 years, to 2.3 children per couple, just above replacement level fertility.
But these successes showed no clear correlation with development, as measured by the growth of a country's gross national product. Some countries, such as South Korea and Taiwan, showed the expected fertility declines associated with rising GNPs, but others, such as Mexico and Brazil, underwent considerable development with little or no reduction in birthrates. And in many developing nations, birthrates remained high despite substantial drops in infant and child mortality, the existence of family planning programs, and development assistance.
By 1980, it had become apparent that, although industrial development might raise the GNP, it had no consistent relationship to the number of children women bore. But certain kinds of development--improving basic health and nutritional conditions, providing for security in old age, and educating women and granting them a measure of independence and economic opportunity--did make a difference, sometimes a dramatic one. The more that improved living conditions and social security were widely distributed, the more effectively they seemed to influence the entire population to have smaller families.
It is essential to distinguish between the different kinds of development because one thing is certain: The world cannot afford the sort of industrial development that has occurred in rich nations since 1950. The planet's life-support systems can't maintain 5.7 billion people living the overconsumptive lifestyle of the average American--a lifestyle that already causes substantial and possibly irreversible damage to the environment.
OPPORTUNITIES FOR WOMEN HELP EVERYONE
Despite the complexity of the factors that affect reproductive choices, some common threads can guide our actions as understanding evolves. It now seems clear that the kinds of development efforts that do work have to do with people's--especially women's--basic living conditions: health, education, and equality of opportunity.
In nearly all developing regions, there is a strong connection between education of women and lower fertility. Even with a few years of schooling, a young woman may apply her education to better manage her family's health and well-being. She learns to obtain pure water, use sanitary practices, and choose more nutritious foods; as more children survive, the mother becomes more receptive to birth control. Education also often opens opportunities for activities besides motherhood.
In Kerala state in southern India, women traditionally have been treated relatively equitably, and education and health care have long been a priority. Because it is a highly literate society, once a few women began using contraception in the 1960s, knowledge and use soon spread. The average family size, already small by Indian standards, fell from 3.0 children in 1979 to 1.8 in 1991, even though the state remained very poor and there was little or no structural change in the society.
Sadly, prospects for similar declines elsewhere in India may not be as bright. India's average family size is still 3.4 children, one in every eight children dies before age 5, and barely a third of adult women are literate.
Several other Asian nations, however, have succeeded in reducing birthrates. In Thailand, the population has tripled from 20 million in 1950 to 59 million in 1995. To stop this expansion, the government began a family planning program in 1970, which has had dramatic results: In 1970 the average woman bore five children; by 1995 that number has fallen to 2.2. While much credit goes to a vigorous and imaginative public education program, it might not have been so successful without the high literacy rate among Thai women, which during that period rose from 72 to 90 percent.
The benefits of educating women extend far beyond fertility reduction. Closing the gender gap in education (two-thirds of the world's illiterate people are women) turns out to be an important factor in a nation's overall social and economic status. Countries in which women have greater access to education have higher GNPs per capita, and a high level of female literacy is also associated with improvements in health and nutrition, independent of income levels.
Societies in which women have substantial rights also have relatively low fertility rates, as illustrated by most developed nations. In particular, women who work outside the home and earn some income of their own, however small, consistently tend to have fewer children. By contrast, where women have low status, they usually have little or no choice about when or how many children they bear, even though they are responsible for the children's upbringing. If the women do work outside the home, they often do so in family-oriented "informal enterprises," and men retain power over them through culturally ingrained arrangements within families. Thus these women achieve no true economic independence. Since they do not directly reap the benefits, employment may not lower their fertility rates.
WE STILL NEED FAMILY PLANNING
Whatever the basic motivations for family-size decisions may be, there is little question that access to modern contraception and safe abortions can help families stay within their goals. Half of all pregnancies are unplanned and a quarter are "certainly unwanted," according to the World Health Organization; this means that even if other social conditions are not favorable for population reduction, a strong family planning program can reduce fertility.
The most effective programs are bolstered by comprehensive maternal and child health programs. And, increasingly, men are included in family planning services. Support is also offered through social policies that regulate the minimum age for marriage, offer education and work opportunities for women, and provide social security arrangements. Some countries have reinforced the family planning message through housing assignments and tax policies that penalize parents with too many children. India has had vasectomy carnivals, and Indonesian youths who promise not to marry before a certain age and to limit the size of their families are given special recognition.
In the Indian state of Tamil Nadu, the array of tactics now being used is truly impressive, as are the results: Last year, an average family size was down to 2.2 children, close behind Kerala's rate. The backbone of the effort is a network of clinics--some private, some government supported--that provide comprehensive contraceptive and mother-child health services. Family planning counseling is offered--even to mothers-in-law, formidable powers in Indian families.
The ideal family size (illustrated by a logo showing a father, mother, and one child) is displayed on billboards, banners, leaflets, and television. Goals that support smaller families, such as recommended ages for marriage and first childbirth, a target average birth weight, and a minimum pregnancy weight gain are also widely promoted.
Nor are Indian men neglected. One ingenious device is to organize hairdressing salons (frequented more by men than women in Tamil Nadu) as centers of education and contraceptive delivery. Workshops train hairdressers to pass the message, and large jars of condoms are located in salons so men can pick them up free and without embarrassment.
But even without such education efforts, there already exists an enormous unmet need for contraceptives. Although more than half of the world's married women are using birth control, the number of women who wish to avoid pregnancy-, but lack access to contraception, was conservatively estimated to be 120 million in 1990. By the year 2000, the number of people in their reproductive years (ages 15-49) will have increased by 23 percent. So, to achieve even a moderate increase in the rate of contraceptive use, the number of people using modern contraceptives in developing nations will have to double.
To meet this rising need, delegates to the 1994 International Conference on Population and Development in Cairo recommended increasing the annual funding for reproductive health services almost fourfold to $17 billion by 2000. About a third of the funds will go to improving reproductive health programs, and the rest to family planning. The developing countries themselves will supply two-thirds of the money. The balance amounts to only about 10 percent of the total official development aid provided by rich countries in 1991--and barely 0.029 percent of their combined 1993 GNPs. The world cannot afford to do less.
CHANGE BEGINS AT HOME
But runaway population growth is only one component pressuring our life-support systems. The other is overconsumption, which has scarcely been addressed. Those who promote population policies for poor nations should also press for them in rich nations, where each person accounts for so much more environmental damage and resource depletion. Further, rich countries should institute strong consumption reduction policies. This would balance poor nations' needed industrial growth while minimizing the environmental impact of additional development.
The United States should take the lead in both endeavors, although it currently shows little interest in either. American fertility is a shocking exception to the very low rates in most industrialized nations. Although American fertility was below replacement for 20 years, it returned to replacement by 1993 and is still rising. Americans are also the most excessive consumers in the world, and our energy profligacy is exceeded in the developed nations only by the former Soviet bloc. This is shameful in an era when global warming, mainly from burning fossil fuels, poses huge health threats for the next century.
The world is too diverse for any one measure to solve the human dilemma. But one generality is so obvious that failure to see it can only reflect willful blindness: Increasing socioeconomic equity at all levels--between the sexes and among families, social classes, regions, and nations--has great potential for improving the human condition. But rich nations perpetuate poverty in the developing world in a million subtle but powerful ways. Improving the behavior of the wealthy would ultimately be much more effective than simply telling the poor how to change theirs.
Paul R. Ehrlich, Bing professor of population biology, and Anne H. Ehrlich, a senior research associate, work in the department of biological sciences at Stanford University; Gretchen C. Daily is Bing interdisciplinary research scientist at the Center for Conservation Biology at Stanford. This article is adapted from a forthcoming book, The Stork and the Plow (Putnam, 1995).
See "Backlash in Beijing?" (in this issue) and Hot Media for resources.