The desert is a biome that is characterized by low rainfall. It can occur both in tropical regions and in cold climates. The vegetation is sparse, in which cacti are predominant.
These regions are generally close to the lines of the tropics and lose moisture through the trade winds and the action of cold sea currents.
Deserts occupy extensive territories, located mainly in tropical and subtropical areas .
In the northern hemisphere, arid regions cover a wide area, from almost all of North Africa and the Near East (Arabia), part of Asia to Pakistan, China and Mongolia (Gobi Desert).
In North America, they are located in the southwestern United States and northern Mexico (Mojave and Sonora deserts).
In the southern hemisphere, the deserts of the central region of the Australian continent, of Southern Africa (Namibia and Kalahari) and those of South America, in Patagonia and in the coastal zone of Chile (Atacama) and Peru, stand out.
Precipitation is very low and can occur in any season. This absence of rain is a challenge for the living beings that live there.
In addition, temperatures vary widely between day and night, reaching a thermal difference of 35 ° C. The winds are constant and often very violent, causing sandstorms.
The soil of the desert regions is very shallow, with a sandy surface covered by a mantle of stones and gravel.
The wind is an agent of permanent erosion of this type of soil; Sand dunes can occasionally be carried by the winds, but, contrary to what one might think, they do not constitute the dominant landscape.
Vegetation is scarce and adapted to an insufficient water supply. The cacti stand out in America and palm trees in Africa and Asia; in addition, clumps of herbaceous plants also occur.
There are plants capable of storing water, such as cacti, while others (such as certain shrubs) develop very deep roots, capable of reaching the water table.
Many species of desert plants have fast vital cycles: they sprout, grow, flower and bear fruit very quickly, when there is a supply of rainwater. Then they die and only the seeds remain, waiting for a new rain so they can sprout and restart the cycle.
The plant in the photo above is endemic to the Namibian desert, where environmental conditions are extremely strict: it rains only every four or five years, with annual rainfall of less than 2 mm.
The desert fauna is adapted to the extreme conditions of these places. Many animals are nocturnal, as during these hours the heat and evaporation are less than during the day. Others take shelter under rocks or inside lairs, such as scorpions and reptiles.
To prevent water loss, camels reduce their sweating and obtain energy by degrading the fat stored in their hump.
Coyote, cougar and rattlesnake are some of the desert animals in America; there are also abundant insects that, like plants, are adapted to the occurrence of occasional rain.
Desert animals, such as the gazelle and the camel, usually have a light colored coat, which reflects heat better than the dark ones.