Water scarcity threatens food in the '90s.

Water scarcity threatens food in the '90s

The world is growing increasingly reliant on irrigated agriculture for its food. Irrigated lands, which account for only 17 percent of the area under cultivation, today yield one-third of the global harvest, notes Sandra Postel, a senior researcher with the Worldwatch Institute in Washington, D.C. Through most of the 20th century, per-capita irrigated agriculture expanded faster than world population. But that trend peaked in 1978, and in the years since, the global per-capita acreage devoted to irrigated agriculture has dropped by 6 percent. Moreover, a number of factors seem likely to hold or further depress the per-capita irrigated average, jeopardizing world food supplies in the coming decade, Postel reported in a study released last week.

The costs of developing new irrigation systems are increasing everwhee, she found. In India, for example, costs of surface-water projects "more than doubled" between 1950 and 1980. Meanwhile, Postel notes, the world's major financers of Third World development projects cut their lending for water projects by 60 percent between 1977 and 1988. And money is sorely needed, she says, not just to expand irrigation but also to maintain existing systems. Postel found that some 60 percent of all current irrigated systems need some form of upgrading, much of it to counter salinization (SN: 11/10/84, p.298).

The search for affordable water is prompting farmers from Texas to china to overpump groundwater at nonsustainable rates, she says. In the rich fruit-and-vegetable basket of Soviet Central Asia, farmers have diverted so much water that the surface area of the Aral Sea -- the world's fourth-largest lake -- has shrunked by 40 percent since 1960. And throughout the world, cities are diverting irrigation water to slake the thirst of their growing masses. Postel says she suspects the water crisis will come to a head first in Egypt, where water supplies just barely meet demands and a population of 55 million is growing by another million every eight months.

To cope, she recommends that governments consider: reducing water subsidies, which discourage conservation of this limited resource; parceling out irrigation water more conservatively; targeting more funds toward boosting crop yields on rain-field lands; and limiting population growth to slow the growing demand for the globe's tightening water supplies.