Desertification and its effects on wildlife

Deserts all over the world are advancing because of both climatic change and human mismanagement. As people collect firewood and cattle destroy tree cover, the land dies- and with it, wildlife.

Desertification in ancient times

In the Near East, the plains be-tween the Tigris and Euphrates rivers formed the ancient region of Mesopotamia. This area was known for its agricultural wealth, but it became an early victim of desertification brought about by humans.

Ancient farmers knew that periodically leaving land fallow or unplanted, helped to renew the soil’s fertility. But they stopped this practice so that they could grow more crops.

After 3000 B.C. irrigation be-came more widespread, proba-bly in response to a population increase. As a result, the soil be-came exhausted. Its fertility was also decreased by a buildup of salts left behind by evaporated irrigation water. Eventually the once lush plains became a des-ert, and the ancient Mesopo-tamian civilization collapsed.

Changing enviroments

At one time the lands north of Africa’s Sahara Desert supported a wide range of wildlife. Ancient rock paintings, murals in tombs, and Roman mosaics all depict deer and gazelle in grasslands, with predators such as leopards and lions hunting them.

Under Roman rule, North Af-rica produced vast quantities of cereal grains such as barley and wheat. However, centuries of overgrazing by cattle, as well as harm to shrubs and trees by goats, have combined with cli-matic shifts to erode the land and destroy wildlife. Tunisia, for example, has lost approximate-ly half its arable land.

Some scientists believe desertification reintorce itself ~y in-tensifying the changes in the climate. Whenever vegetation is destroyed on a large, long-term scale, ground temperature rise and rainfall decreases. In 1969 the Israelis built a fence across the Sinai-Negev Desert between Israel and Egypt. On one side the Egyptians contin-ued grazing camels, sheep, and goats. On the other side the Is-raelis left the land uncultivated, and wild plants began to take hold. Satellite photographs re-veal dark patches of vegetation under hazy cloud cover on the Israeli side but a clear sky and a desert in the making on the Egyptian side.

Vanishing wildlife

Desertification makes areas at the edges of a desert inhospi-table to wildlife. Grazing cattle, foraging goats, and people col-lecting firewood strip the plant cover, and livestock trample the topsoil to dust. Native animals then starve, including unique species especially adapted to a semiarid habitat.

At the end of the last Ice Age 12,000 or so years ago, the Arabian Peninsula supported grass-lands and savanna, and juniper forests covered the mountains to the west. Wildlife flourished. But climatic changes reduced the forests and grasslands, and this process was continued by growing human communities. Recently, oil revenues have fi-nanced huge increases in graz-ing livestock and big agricultural projects using large amounts of water. The new livestock have pushed the Bedouins’ camel herds farther afield to graze. The Arabian deserts still con-tain species that have adapted to the arid conditions, and ga-zelles, wolves, foxes, and hares live at the deserts’ edges. But the fringes are threatened by insecticides used to kill malari-al mosquitoes and crop-eating insects such as locusts. These chemicals have also reduced insects that feed other animals and pollinate many plants.

Another threat to the fringes comes from an increased num-ber of sheep and goats. Within a fenced area, these grazing animals will strip the ground bare, while the land outside continues to flourish.

Reclaiming deserts

Modern agriculture has devel-oped many techniques for in-creasing food production. For example, large-scale irrigation projects can turn arid deserts into green oases. But the gain is often temporary unless long-term soil management and re-forestation are undertaken.

Irrigation of arid lands has led to desertification in many parts of the world. The buildup of salt left behind when water evaporates has harmed soils in agricul-tural regions such as California’s Imperial Valley. In Africa and the United States, as well as in other areas, pivoted irrigation systems spread water over crops, creat-ing bright green circles. At the same time, however, these sys-tems pour fertilizers and insect killing pesticides into the soil. Al-though the chemicals help pro-duce two crops per season, the soil structure deteriorates with-out organic additives. Also, the chemicals wash into nearby wa-terways, poisoning fish as well as birds and other animals.

Although difficult, it is possible to reclaim newly formed deserts by replanting. As the vegetation grows, the climate gets moister and wildlife begins to return.