Desert Biomes

A desert is a biome defined by very low precipitation, where the amount of water lost through evaporation greatly exceeds the amount that falls as rain. This scarcity of water, rather than heat alone, is the defining feature of a desert, which is why some deserts are hot while others are cold. Deserts cover a large fraction of the Earth's land surface and are often grouped together as drylands. The Sahara in northern Africa is the largest hot desert, and dramatic landscapes such as the Grand Canyon lie within arid regions.

Deserts fall into several types. Subtropical deserts form near the tropics where descending dry air suppresses rainfall. Cool coastal deserts arise along certain shorelines where cold ocean currents limit precipitation. Cold winter deserts experience freezing seasons, and the polar regions are sometimes classed as cold deserts because they receive very little precipitation. Wind and infrequent water shape desert surfaces into features such as sand dunes, rocky plains and dry channels, a field studied as desert geomorphology.

Life in the desert is adapted to conserve water and tolerate extremes. Plants such as cacti and other succulents store water in thick tissues and reduce water loss with small or spine-like leaves, while many desert wildflowers bloom rapidly after rare rains. Desert animals often shelter from the daytime heat, are active at night, and obtain much of their water from food. These adaptations allow surprisingly varied communities to persist despite the harsh climate.

Frequently asked questions

What defines a desert?

A desert is defined by very low precipitation and high potential evaporation, so that water is chronically scarce. This can occur in hot regions or in cold ones.

Are all deserts hot?

No. Some deserts are hot, but cold winter deserts and the polar regions are also deserts because they receive very little precipitation.

How do cacti survive in deserts?

Cacti are succulents that store water in thick stems, have spines instead of broad leaves to reduce water loss, and use shallow, wide-spreading roots to capture rainfall quickly.