Word: semiarid
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Dates: during 1970-1979
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Because the semiarid region is ecologically fragile, reports AID, "mistakes in the use of soil, water and vegetation are magnified." Trees have been cut down for fuel, savannah grass has been replaced by seasonal crops, and available ground water has been squandered. Most damaging of all, the inhabitants have allowed their huge herds of livestock to denude the land through overgrazing. These practices, combined with the drought, have killed off the natural vegetation and allowed the Sahara to creep southward-in some places, says AID, by "as much as 30 miles a year...
...company has regraded the land and planted trees and several species of grass for a total cost of $700 an acre, which adds only pennies per ton to the total cost of obtaining coal. But local farmers and ranchers are not convinced, because reclamation is extremely difficult in the semiarid region (average rainfall: 14 in. per year). "If I used as much fertilizer as they did on that test site," says Rancher Wally McRae, "I could grow grass on the roof of my house...
...photograph that has caused the most excitement among scientists shows a 250-mile-long valley that resembles an arroyo (a water-cut gulley common in semiarid regions on earth). The valley is 3½ miles wide and has branching, streamlike tributaries that seem more likely to have been formed by water than by lava. "We are hard put to find a mechanism other than running water for these features," says Harold Masursky of the U.S. Geolog ical Survey. Although scientists agree that there is no free-flowing water on the Martian surface now, the sharp and uneroded features...