Desert Biomes: Dry, But Full of Life

Beyond the sun and sand, here's what you need to know about the world's deserts.

Sahara Desert
Sunset over the western part of The Sahara Desert in Egypt. The Sahara Desert is the world's largest hot desert. (Photo: hadynyah/Getty Images).

If you think all deserts are just sand and sun, think again. There is actually a lot more going on in many desert environments than you realize.

A desert is characterized by its lack of precipitation. Deserts are often described as areas where more water is lost to evaporation than is received from precipitation. Many deserts see less than ten inches of rain per year.

This lack of water makes it difficult for most plants and animals to survive.

But some have been specially adapted to endure a desert's harsh environment. Animals such as reptiles and small mammals like kangaroo mice do well in desert environments. Many desert animals are nocturnal which helps them avoid daytime temperatures. Cacti and other water-conserving plants also thrive in a desert environment. Some desert plants have deep root systems that allow them to tap into water sources well below the desert surface. 

Because of their harsh environments, deserts are also prone to extreme weather conditions such as fires, flooding, dust storms, and of course, drought. 

Right now, deserts and semi-arid areas make up about one-third of the Earth's surface. They can be classified by their geographic location, the amount of precipitation in the area, or by their average temperature. The four main categories of desert are hot, cold, semi-arid, and coastal. Here's a bit more information about each of these desert types:

Hot. Hot deserts are known for their high summer temperatures and low levels of precipitation. These deserts often see wide temperature variations between winter and summer and even day and night. What little rainfall does occur in hot deserts generally falls all at once in infrequent bursts throughout the year.

This leads to flooding which is then followed by long dry periods. The four major North American hot deserts are the Chihuahuan, Sonoran, Mojave and the Great Basin. Hot deserts also occur in southern Asia, South and Central America, Africa, and Australia. 

Cold. These deserts are characterized by long, cold winters with moderate amounts of snowfall followed by short, warm summers. They are found in Antarctica, Greenland, Central Asia, southern Australia, and on the eastern side of the Rocky Mountains.   

Semi-arid. As their name suggests, semi-arid deserts see slightly more rainfall than other desert types. Summers are generally hot and dry with most rainfall falling in the winter months. Semi-arid deserts may see anywhere from 8 to 20 inches of rain per year. They are found in Utah, Montana, and the Great Basin in the U.S. as well as around the world in Newfoundland, Greenland, Russia, Europe, and northern Asia.

Coastal. Coastal deserts are known for their cool winters and warm winters. A such, they tend to see less extremes in temperature variation than other desert types. Coastal deserts usually occur on the western edge of a land mass and many are bordered on the east by mountains.

What moisture these areas do get usually comes in the form of fog or dew. The Atacama Desert in Chile is a coastal desert, as are some of the deserts found in California, south-west Africa, Mexico, and Australia. 

In addition to the large deserts that are already found on the Earth, such as the Sahara Desert, the Gobi Desert, and the Kalahari Desert, there are a few environments in the world that are turning into deserts. This process, known as "desertification," is human-caused and is typically the result of climate change, overpopulation, and over-use of the land for agricultural and livestock purposes.