dunes, however, while the remainder is a another rain. These are the desert plants rocky or pebbly desert. grazed by nomadic tribesmen’s herds of This is a tropical desert where the camels and horses. These nomads con- world’s record high temperature of 136.6 stantly follow the greening of the desert, F (58.2 C) occurred in Azizia, Tunisia. just as do Africa’s game animals. Daily high temperatures regularly top There are some oases scattered across 100 F (37.8 C) throughout the high sun the Sahara, but only about 90 have large period from June through August. Day- permanent settlements surrounding time relative humidity often drops below them. Most of the remaining oases are 10 percent, making daylight outdoor ex- watering holes and shallow wells, used ertion dangerous. by small villages and the nomads’ herds. As in all true deserts, potential evapo- Some of the lesser oases are hundreds of ration exceeds precipitation. This means miles apart and their dependability may that there is no long-term net moisture be poor. This makes travel especially dan- THE SAHARA accumulation. All desert plants have gerous for non-natives. evolved mechanisms for either conserv- Along the southern fringe of the Sa- WOBBLE ing moisture or completing rapid life hara is a semidesert grassland, called a The Sahara, the world’s largest desert, cycles. For example, the cactus’s pulpy tropical steppe. This is the infamous Sahel, covers much of North Africa. But it was body retains moisture through extended whose climatic variations are legendary. not always desert. About 6,000 years ago, dry periods. Its needles are its leaves, This region often experiences lengthy the region was covered in lakes and grass- which release no moisture, and its root droughts and advancing desertification. lands with abundant animal life. In only system is deep and broad. Unlike the Sahara, numerous villages dot 2,000 years, the desert took over. Rain does come to the Sahara, but it the Sahel. When drought comes, the natu- The speed with which desertification typically consists of scattered thunder- ral plant life comes under severe stress. occurred fascinates a host of scientists storms. Often such storms bring a whole Villagers’ cattle overgraze the meager veg- searching for causes of this climatic phe- year’s rain in a single 30-minute down- etation and women and children are nomenon and the natural cycle that caused pour. Because there is so little natural forced to go farther and farther for water it. It may have implications for under- vegetation to hold the moisture, runoff is and firewood. If the rains don’t soon re- standing current climatic changes, as well rapid. Runoff temporarily collects in dry turn, death and mass migrations occur. as help explain ancient changes in human washes, called wadis, as it roars down The Sahel’s droughts may give us hints patterns in the Middle about potential human im- East. pacts as the Sahara’s grass- A computer simu- Desertification in Desert lands 6,000 years ago gave lation recently led cli- North Africa Areas subject way to desert. Whether or matologists at to desertification not the Northern Hemi- Germany’s Potsdam sphere cooling came about Institute for Climate because of an orbital wobble, 0 1000 mi Impact Research to the Sahara quickly became ©1999 maps.com drier. suspect that only glo- S a hara 0 1000 km bal climate change With a prolonged de- could have been re- sertification, there is some sponsible for such a conjecture that this may have rapid change in Af- S a hel initiated large regional mi- rica. They suspect that S a h el grations. Perhaps peoples Lake fleeing increasingly stressful a wobble in the earth’s Chad axis and a shift in its Sahara droughts while seek- orbit might have been Lake ing more predictable water the cause. But the ef- Turkana supplies influenced the Nile Lake Albert fects on the Sahara re- Geography in the News (10/22/99) civilization. Source: After Goode’s World Atlas, 19th ed. Lake Victoria gion and its people We certainly know a had to be monumen- great deal about the processes tal. slope in fierce walls of water, dirt and and implications of desertification. What Today, the Sahara covers more than debris. Anyone unlucky enough to be is just now being learned is how the natu- 3.5 million square miles (9 million sq. trapped in these flashfloods has little ral climatic cycles are occurring, what km), an area nearly as large as the United chance of surviving. Usually, the victim is role anthropogenic, or human, activities States. Its east-west distance is 3,500 miles not even aware of impending disaster, may play, and how humans adapt to cli- (5,635 km.), and its north-south distance since the storm may have occurred miles matic change is 1,200 miles (1,932 km.). away. And that is Geography in the News, The Sahara is a desolate place, but its Following a rain, the desert may turn October 20, 1999. green for a few weeks, as grasses and beauty lies in its barren rock, shifting (The author is a professor of Geography at flowers flourish for brief periods. They sands and long vistas. Only about 10 per- Appalachian State University, Boone, NC.) complete their life cycles quickly and await cent of the total region contains sand #491  1999 Reproduced from subscribing newspapers