Deserts are unique ecosystems characterized by extreme aridity, meaning they receive very little precipitation. These environments are found across the globe, covering about one-fifth of the Earth’s land surface. While often envisioned as hot, sandy expanses, deserts encompass a diverse range of landscapes, each shaped by its specific environmental conditions. Exploring their global distribution reveals how different geographical and atmospheric factors contribute to their formation.
Defining Desert Biomes
A desert biome is defined by extremely low annual precipitation, typically receiving less than 250 millimeters (10 inches) of rain. This limited rainfall leads to high evaporation rates. Deserts often experience significant temperature fluctuations, with scorching daytime heat followed by surprisingly cold nights, due to the dry air’s inability to retain warmth. Life forms in these environments exhibit specialized adaptations to survive with minimal water and cope with temperature extremes.
Major Hot Desert Regions
Hot deserts are typically located between 15° and 35° latitude, both north and south of the equator. The Sahara Desert, stretching across North Africa, is the world’s largest hot desert, encompassing over 9 million square kilometers. East of the Sahara, the Arabian Desert dominates much of the Arabian Peninsula. In South America, the Atacama Desert in Chile is one of the driest places on Earth, with some areas experiencing virtually no rainfall for years.
North America is home to several hot deserts, including the Sonoran Desert, which extends across parts of Arizona, California, and Mexico. The Mojave Desert, known for its Joshua trees, is also found in the southwestern United States. Australia features hot deserts, such as the Great Victoria Desert, the Great Sandy Desert, and the Gibson Desert, covering significant portions of the continent’s interior. These regions often feature vast stretches of sand dunes or rocky plains.
Major Cold Desert Regions
Cold deserts experience extreme cold and low precipitation. These are often found at higher latitudes or elevations.
The Gobi Desert, spanning large parts of Mongolia and China in Central Asia, is an example of a cold desert. It experiences frigid winters and can have significant temperature variations between seasons.
In North America, the Great Basin Desert, located across Nevada, Utah, and parts of surrounding states, is another cold desert with high elevation and cold winters. Polar regions also contain polar deserts, such as those found in the Arctic and Antarctic. These areas receive very little precipitation, primarily in the form of snow, and are defined by consistently freezing temperatures.
Common Drivers of Desert Formation
Several interconnected geographical and atmospheric phenomena contribute to desert formation. High-pressure zones, often found around 30 to 35 degrees latitude, cause dry air to descend, preventing cloud formation and precipitation. This mechanism is a primary driver for many subtropical deserts, including the Sahara and Arabian Deserts. Mountain ranges can create a “rain shadow effect,” where moisture-laden air is forced to rise and cool, releasing its precipitation on one side of the mountains. The leeward side then remains dry, as seen with the Atacama, Great Basin, and Gobi deserts. Cold ocean currents, such as those off the coast of Chile and Namibia, cool the air above them, reducing its capacity to hold moisture and leading to coastal deserts. Continentality, or distance from large bodies of water, means air masses lose most of their moisture before reaching the interior of large continents, contributing to the aridity of regions like the Gobi Desert.