A desert is a type of ecosystem fitting under the category of biome.  Deserts are extremely dry, and their unique conditions cause highly different plant and animal life to exist.

In order to be considered a desert, an area must receive less than 10 inches (25 centimeters) of precipitation annually.  Also, an area where evaporation is considerably greater than precipitation, which means it is very dry, might also be considered a desert.  A third definition of a desert is an area not capable of supporting life.

A Desert.  Photo Credit: ClickArt Image Pak.

The most common areas for deserts to occur in are 30 degrees north and south of the equator.  Here, large dry air masses come down to the earth and produce the desert areas.

Desert land is expanding through the problem of desertification.  Through human wreckage of soil, desert areas are expanding and the total amount of desert in the world is growing.

There are three classifications of deserts.  Deserts such as the Sahara are known as hot deserts, those like the Mojave are temperate deserts, and those like the Gobi are cold deserts.

In the future, deserts could play an interesting role in meeting the world's energy needs.  Because deserts tend to be uninhabited, dangerous waste materials could be stored in them.  Also, solar energy collectors could be placed in deserts to generate power.