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A camel caravan crosses part of the Gobi Desert near Dunhuang in western China. Although the Gobi Desert is a region of temperature extremes and harsh conditions, it is also home to many animals, including Bactrian camels, gazelles, small cats, and other creatures.

What Is a Desert?

A person asked to describe a desert would probably use words such as “sandy,” “flat,” “hot,” and “lifeless.” Yet deserts are not necessarily sandy, are often hilly, are sometimes cold, and are hardly ever completely without life. Scientists define a desert as a region that loses more water into the air as water vapor than it receives as precipitation in the form of rain, snow, sleet, hail, dew, or frost. Deserts lose water as vapor in two ways. When water is heated by the sun it begins to evaporate, or turn to vapor. Plants also soak up water at their roots and breathe it out as vapor, in a process called transpiration . Arid deserts receive less than 10 inches (25 cm) of precipi- tation each year. There is hardly any cloud above them during the day, and the sun heats the desert surface very quickly. The dry desert air cannot hold onto this heat at night, which is why

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