![]() This process, known as desertification, is not caused by drought, but usually arises from deforestation and the demands of human populations that settle in semiarid lands. Deserts, Land Use, and Climate Change Some of the world's semiarid regions are turning into desert at an alarming rate. Other plants, such as cacti, have special means of storing and conserving water. Some plants have adapted to the arid climate by growing long roots that tap water from deep underground. Desert plants may have to go without fresh water for years at a time. Because of their very special adaptations, desert animals are extremely vulnerable to changes in their habitat. And among insects, the Namib desert beetle ( Stenocara gracilipes) can harvest fog from the air for water. Most desert birds are nomadic, crisscrossing the skies in search of food. Some animals, like the desert tortoise ( Gopherus agassizzi) in the southwestern United States, spend much of their time underground. Many desert animals, such as the fennec fox ( Vulpes zerda), are nocturnal, coming out to hunt only when the brutal sun has descended. Camels can go for weeks without water, and their nostrils and eyelashes can form a barrier against sand. Desert Animals and Plants Desert animals have evolved ways to help them keep cool and use less water. On the other hand, every few years, an unusually rainy period can produce "super blooms," where even the Atacama becomes blanketed with wildflowers. Such environments are so harsh and otherworldly that scientists have even studied them for clues about life on Mars. The driest deserts, such as Chile's Atacama Desert, have parts that receive less than two milimeters (0.08 inches) of precipitation a year. Only about 20 percent of deserts are covered by sand. But some deserts are always cold, like the Gobi desert in Asia and the polar deserts of the Antarctic and Arctic, which are the world's largest. The largest hot desert in the world, northern Africa's Sahara, reaches temperatures of up to 50 degrees Celsius (122 degrees Farenheit) during the day. Despite the common conceptions of deserts as hot, there are cold deserts as well. These areas exist under a “moisture deficit,” which means they can frequently lose more moisture through evaporation than they receive from annual precipitation. Deserts are part of a wider class of regions called drylands. A place that receives less than 25 centimeters (10 inches) of rain per year is considered a desert. What Is a Desert? Deserts cover more than one-fifth of Earth's land area, and they are found on every continent. Yet more than one billion people, one-sixth of Earth's population, actually live in desert regions. Some deserts are among the planet's last remaining areas of total wilderness. Far from being barren wastelands, deserts are biologically rich habitats with a vast array of animals and plants that have adapted to the harsh conditions there. ![]()
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