Some deserts, such as the Mojave and the Sahara, are sandy, sun-baked wastelands; others, such as the frigid polar deserts of Antarctica and the Arctic, are covered with snow and ice. The one thing all deserts have in common is aridity, or lack of water, yet there is life in the desert including plants, animals and even human communities, all of whom have learned to adapt to the harsh desert environment.
Deserts cover approximately one-third of the earth’s surface. At least thirty nations, most of them located in the Middle East and Africa, are 75 percent desert. The longest stretch of arid land is the Saharan-Arabian-Iranian-Thar Desert, which extends across North Africa and the Middle East into northwest India. The largest desert is the Sahara, which covers 3.5 million square miles.
Deserts receive less than 10 inches of rain per year. There have been cases when the combination of high heat and dry winds has caused rain to evaporate before it hit the ground. One of the hottest places on earth is Death Valley, located on the border between California and Nevada, where the ground surface temperature has soared to 190 degrees F, the highest on record. The coldest desert temperature on record was reported in Antarctica at -129 degrees F.
Because water is scarce in deserts, life forms tend to be limited. The widest variety of plants and wildlife is found in the Sonoran Desert, which straddles the United States and Mexico. This arid place is home to more than 3,000 species of plants, 500 species of fish, amphibians, mammals and birds, and thousands of insects, including 1,200 different species of bees.
Contrary to popular opinion, not all deserts are sandy. The Sahara is 70 percent gravel. In the Mojave you’ll find dry alkaline lakebeds and dunes of calcium carbonate, the main ingredient used in lime for fertilizer. Lava and salt basins cover Chile’s Atacama Desert, while the Arctic presents an endless horizon of snow and icy glaciers.
The kangaroo rat, a species found in the deserts of the western and southwestern United States, can survive entirely without water. It derives all the moisture it needs from mesquite beans and the seeds of desert grasses that are its primary sources of food. Spadefoot toads remain dormant for long periods, waiting for rain before they reproduce. And mesquite trees can sink their roots 150 feet deep in search of underground sources of moisture.