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National Geographic : 1979 Nov
Contents
that plunges to 436 feet below sea level. The Sahara's dryness begins at the Equa tor. There in the rainy tropics hot air rises and sheds its moisture as it cools. The cooled air begins to subside and warm up again be tween 150 and 30 ° north latitude. The subsid ing air is too dry for clouds and rain to form. This subtropical high-pressure belt parches the earth from the Sahara through the Mid dle East and into northwestern India and Pakistan. It helps create the American des erts. A similar belt south of the Equator leads to the arid sands of the Kalahari and Namib Deserts of Africa as well as the deserts of Peru, Chile, and Australia's barren outback (map, pages 604-606). In the past 65 million years the borders of the Sahara have expanded and retreated many times. Oak and cedar trees once grew in the Saharan highlands, and rock paint ings portray abundant wildlife. But about 3000 B.C. the current desiccation began set ting in, and man, a relative newcomer to North Africa, had to contend with desertifi cation of the worst degree. North Africa's rich granaries that once fed the Roman Empire have vanished. Tunisia has lost perhaps half its arable land. Algeria is planting a greenbelt of trees to keep the desert away, and there has been talk of ring ing most of the Sahara with such a living Maginot Line. Yet in only a few places is the desert ad vancing like an army of sand. The war is being lost in patchwork battles from within. A piece of land goes here, another dies there. The enemy is no longer just the climate. It is ourselves and our animals, chopping trees for fuel, clearing marginal lands and cultivating their fertility away, and grazing grasslands to death. In good years the lean resources of these dry lands are strained, so that each time a drought hits, the collapse is more terrible, the recov ery more doubtful. In 1968 severe drought struck the south ern frontier of the Sahara, a region called the Sahel. As many as 250,000 people and mil lions of animals died over the next six years. In 1974 reasonable rains returned for a few years, but when I visited the Sahel last year, drought had descended once more in places. The millet crop along the Senegal River had failed. Timbuktu was on the The Desert:An Age-old Challenge Grows brink of famine. In Nouakchott, the capital of poor, mammoth Mauritania, the past rainy season had lasted only a few hours. Drought-browned Nouakchott teems with refugees (page 615). Moorish nomads in flowing blue boubous and Negro millet farmers up from the deteriorating fields along the Senegal River cram into two shan tytowns. Herds of wandering goats and camels have chewed back what scant vege tation exists. Sand drifts in the streets, cov ering mounds of trash. Overhead the sun moves dimly through a pale yellow haze. Outside a refugee tent a young boy feeds cardboard to his cow. At the goat market a lone acacia tree sits fenced off in the sand. Someone wants to save it from the goats, or from neighbors who would lop its limbs for charcoal or fence posts. Before the 1968 drought 65 percent of Mauritania's million people were nomads. By 1976 that figure was down to 36 percent. Nouakchott has grown from 12,300 in 1964 to about 135,000 today. At a medical station a teacher sits with three other brightly garbed women reading French magazines. They are oblivious to the flies on their hands and faces. Most people come to Nouakchott, she says, because there is no means of earning a living in the country any longer. Will the drought continue? "Al lah will answer," she says. LIMATOLOGISTS, meanwhile, are debating whether drought in the Sahel is a short-term aberration or the onset of a long-term climatic change. Many argue that the drought feeds on itself, that as vegetation is stripped from the land, the sur face dries out and reflects more of the sun's heat. This would alter the thermal dynamics of the atmosphere in ways that suppress rainfall. Others suspect that increased dust or other atmospheric pollutants could be causing desertifying changes in the climate. "The people in Nouakchott are mostly tired," says Nicole Sandoz, a nurse at the medical station. "In way of life, I don't know what's best for them, this or the desert. Their health is much worse here with the bad water and sanitation. Maybe they are happier squashed together like this. But still, when you see the children, how dirty they are, their (Continuedon page 602) 597
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