World population, agriculture, and malnutrition.

• Author: Pimentel, David

Increases in food production, per hectare of land, have not kept pace with increases in population, and the planet has virtually no more arable land or fresh water to spare. As a result, per-capita cropland has fallen by more than half since 1960, and per-capita production of grains, the basic food, has been falling worldwide for 20 years.

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Entering the new millennium, stark contrasts are apparent between the availability of natural resources and the demands of billions of humans who require them for their survival. According to the Population Reference Bureau, each day almost a quarter-million people are added to the roughly 6.4 billion who already exist. Yet the stocks of natural resources that support human life--food, fresh water, quality soil, energy, and biodiversity--are being polluted, degraded, and depleted.

Global population has doubled during the last 45 years. If the present growth rate of 1.3 percent per year persists, the population will double again within a mere 50 years. Growth rates vary from one country or region to another. For example, China's present population of 1.4 billion, despite the governmental policy of permitting only one child per couple, is still growing at an annual rate of 0.6 percent. Although China recognizes its serious overpopulation problem and recently passed legislation strengthening the policy, its young age structure means that the number of Chinese will continue to increase for another 50 years. India, with nearly 1.1 billion people (living on approximately one-third the land of either of the United States or China), has a current population growth rate of 1.7 percent per year. This translates to a doubling time of 41 years. Taken together, the populations of China and India constitute more than one-third of the total world population. In Africa, despite the AIDS epidemic, the populations of most countries also are expanding. The populations of Chad and Ethiopia, for example, are projected to double in 21 and 23 years, respectively.

But the problem is hardly confined to the developing world. The U.S. population--among the most heavily consuming in the world--is growing rapidly. Now standing at nearly 300 million, it has doubled during the past 60 years. The U.S. Bureau of the Census reported in 2003 that sustaining the current growth rate of about 1.1 percent per year will double the population to 600 million in less than 70 years.

Current United Nations estimates of population stabilization at about 9 billion people by 2050 are questionable, mainly because of the very young age structure of the current world population and the momentum it fosters. A large share of the population is concentrated within the 15-to-40 range, where reproductive rates are high. Even if all the people in the world adopted a policy of only two children per couple, it would take approximately 70 years before the world population would finally stabilize at about 12 billion, twice the current level.

Land

Many human beings already suffer from hunger and/or malnourishment. The United Nations Food and Agricultural Organization (FAO) reports that the quantity of food produced per capita has been declining since 1984, based on available cereal grains, which make up about 80 percent of the world's food supply. Although grain yields per hectare in both developed and developing countries are still increasing, the rate of increase is slowing. According to the U.S. Department of Agriculture, U.S. grain yields increased at about 3 percent per year between 1950 and 1980, but since then the annual rate of increase...