CONTENTS
HIGHLIGHTSPopulation Reports is published by the Population Information Program, Center for Communication Programs, The Johns Hopkins School of Public Health, 111 Market Place, Suite 310, Baltimore, Maryland 21202-4012, USA
December, 1997 |
Logically, population growth must stop at some point, or the earth would become overcrowded and its resources eventually would be depleted. The term "carrying capacity" refers to the number of people that the earth can support on a sustained basis—that is, support indefinitely at a constant standard of living without destroying the natural resource base. There is no way to predict how large the population could become, however, before it overwhelmed the planet. Nor is there any way to predict the quality of life in the future under the almost infinite variety of scenarios for population growth, consumption patterns, food production, technological change, natural resource use, air and water pollution, land degradation, and many other factors (15, 33, 42). The question of carrying capacity has been debated for 200 years, since 1798, when the English economist Thomas Malthus published his Essay on the Principle of Population as It Affects the Future Improvement of Society. Malthus reasoned that, since productive land and potable water are finite resources, population growth inevitably would outstrip the food and water supply at some point. Mass starvation and anarchy would follow (57). The Middle Ages in Europe provided many tragic examples for Malthus. Europe's population had risenfrom about 36 million in the year 1000 to 80 million in 1300, while new technology, or innovations of any kind, were unknown. By 1300 good farmland was virtually exhausted. As more people tried to live from the same amount of cropland, food prices rose beyond the reach of the poor (that is, beyond the reach of nearly everyone except the clergy and nobility). Devastating famines ravaged the land in 1316 and 1317. Then in 1346 the Black Plague struck. By the end of the century it had killed one-third of the entire population of Europe (69). Malthus failed to anticipate the subsequent leaps in agricultural technology and economies of scale that have enabled world population to rise to nearly six billion. Today, however, scientists warn that the planet may be increasingly at risk in the future. As biologists Peter Vitousek and colleagues argue, at current levels of population and technology, human activities cause "rapid, novel, and substantial changes" to the earth's ecosystems. These include degrading soil and water supplies; altering nature's cycles, largely by releasing enormous amounts of carbon dioxide into the atmosphere; and destroying or altering biological resources, even driving some plant and animal species into extinction. Reducing the pace of human impact on the earth's natural systems might give natural systems more time to adjust. The two basic ways of slowing the growth in human effects on the Earth, they advise, are to slow population growth and to use resources more efficiently (124). While no one can accurately predict the distant future, the final outcome of the race between population growth and food supply is likely to hinge on the answers to several questions:
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