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Deforestation can set in motion forces that reduce the amount of rainfall in a given area. In a rain forest, for example, as much as half the moisture settles on trees and quickly evaporates into the sky, only to precipitate again in a continuous cycle. Thus when trees are cut down, rainfall may diminish.
Even in dryer regions sparse shrubs can help maintain rainfall. Some scientists argue that once ground cover is stripped, the land hardens and evaporates less moisture into the air. At the same time, the naked soil reflects more sunlight, triggering atmospheric processes that reduce rainfall by drawing dryer air into the area.
The result is desertification, a gradual conversion of marginal land into wasteland. This process is often driven by population pressures, which force people to work lands unsuitable for agriculture. In sub-Saharan Africa, for instance, settlers move into an area when it is wet and green, and then stay and remove the ground cover when the inevitable drought returns. Without a green barrier to stop them, sand dunes march inexorably forward.
While no place is safe from the effects of the water crisis, Egypt, in particular, faces hard times. The country's population of 55 million is growing by 1 million every nine months. Already the people must import 65% of their food, and the situation could grow far worse. The flow of the Nile, Egypt's only major water supply, will be reduced in coming years as upstream neighbors Ethiopia and Sudan divert more of the river's waters. Egypt's only practical course is to brake population growth and reduce the enormous amount of water wasted through inefficient irrigation techniques.
Competition for water is especially fierce between Israel and Jordan, which must share the Jordan River basin. Many towns in Jordan receive water only two times a week, and the country must double its supply within 20 years just to keep up with population growth. "We are cornered," admits Munther Haddadin, a Jordanian development official. With time running out, Jordan hopes to draw additional reserves from the Yarmuk river. Israel, however, will fight any plans for use of the river that do not give guarantees of access to the Yarmuk waters that the country currently uses.
In the grip of a three-year drought, Israel too is far from secure, despite its formidable conservation technologies. An expected 750,000 Soviet emigres will probably settle in the cities, where the use of pure water is the highest. At the same time, 750,000 Palestinians in the Gaza Strip face what Zemah Ishai, Israel's water commissioner, calls a "catastrophe" because of overpumping and contamination of groundwater.
A decade ago, a government study in China estimated that the nation's water resources might support only 700 million people. That was alarming, since the population had already reached 900 million. Unable to increase the supply, the Politburo took the simpler expedient of revising the study to conclude that there was enough water for 1.1 billion people. As the population continues to grow and now surpasses the 1.1 billion mark, China has gradually increased the numbers in the study.