Many countries that have experienced rapid population growth for several decades are showing signs of demographic fatigue, a result of the struggle to deal with the multiple stresses caused by high fertility. Countries struggling with the simultaneous challenge of educating growing numbers of children, creating jobs for swelling ranks of young job seekers, and dealing with the environmental effects of population growth, such as deforestation, soil erosion, and falling water tables, are stretched to the limit. When a major new threat arises-such as AIDS or aquifer depletion-governments often cannot cope. Problems routinely managed in industrial societies are becoming full-scale humanitarian crises in many developing ones. As a result, some developing countries with rapidly growing populations are headed for population stability in a matter of years, not because of falling birth rates, but because of rapidly rising death rates.
To understand the widely varying population growth rates among countries, demographers use a three-stage model of how these rates change over time as modernization proceeds. In the first stage, there are high birth and high death rates, resulting in little or no population growth. In the second stage, as modernization begins, death rates fall while birth rates remain high, leading to rapid growth. In the third stage, birth rates fall to a low level, balancing low death rates and again leading to population stability, offering greater possibilities for comfort and dignity than in stage one. It is assumed that countries will move gradually from stage one to stage three. Today there are no countries in stage one; all are either in stage two or stage three. However, this analysis concludes that instead of progressing to stage three as expected, some countries are in fact falling back into stage one as the historic fall in death rates is reversed, leading the world into a new demographic era.
National projections of population growth vary more widely than at any time in history. In some countries, population has stabilized or is declining; but in others, population is projected to double or even triple before stabilizing. In 32 countries, containing 14 percent of world population, population growth has stopped. By contrast, Ethiopia's population of 62 million is projected to more than triple to 213 million in 2050. Pakistan will go from 148 million to 357 million, surpassing the U.S. population before 2050. Nigeria, meanwhile, is projected to go from 122 million today to 339 million, giving it more people in 2050 than there were in all of Africa in 1950. The largest absolute increase is anticipated for India, which is projected to add another 600 million by 2050, thus overtaking China as the most populous country.
As recent experience with AIDS in Africa shows, some countries which have reduced their death rates whilst birth rates remain high are simply overwhelmed when a new threat appears. While industrial countries have held HIV infection rates among their adult populations under 1 percent or less, a 1998 World Health Organization survey reports that in Zimbabwe, for example, 26 percent of the adult population is HIV positive. In Botswana it is 25 percent, Zambia 20 percent, Namibia 19 percent, and Swaziland 18 percent. Barring a miracle, these societies will lose one fifth or more of their adult population within the next decade from AIDS alone. These deaths will bring population growth to a halt or even into decline, with high mortality trends more reminiscent of the Dark Ages than the bright new millennium so many had hoped for.
New diseases are not the only threat to demographically fatigued countries. Because population growth affects so many dimensions of a society, any of several different stresses can force a country back into a primitive stage of development. For example, in many developing countries food supplies are threatened by aquifer depletion. Recent growth in food production and population in India, a country heavily dependent on irrigation, has been based partly on the unsustainable use of water. Nationwide, withdrawals of underground water are at least double the rate of recharge and water tables are falling by 1 to 3 meters per year. It is estimated that as India's aquifers are depleted, its grain harvest could fall by as much as one fifth. In a country where food and population are precariously balanced and which is adding 18 million people per year, such a huge drop in food output could create economic chaos.