According to the World Conservation Union (IUCN), "desert consists of arid landscapes with a sparse plant cover, except in depressions where water accumulates. The sandy, stony or rocky substrate contributes more to the appearance of the landscape than does the vegetation."
Approximately 20% of the Earth is classified as desert habitat. While hot, dry, and sandy places immediately spring to mind when one thinks of a desert, there are actually several different types of deserts:
Hot and Dry Deserts
While these various desert types occur in different places on the Earth, they share a common characteristic in their low levels of precipitation (typically less than 20 inches per year).
Deserts are often mistakenly thought of as wastelands, bereft of life. On the contrary, deserts are very special places biologically, hosting specialized plants and animals that can tolerate low levels of moisture and extreme temperatures. Desert soils often are highly adapted to provide nutrients and substrate while requiring very low levels of water. When water does come to the desert, it often falls in short, sudden, and severe bursts that can cause flash flooding. Another occasional disturbance is fire.