Search results
Although some deserts are very hot, with daytime temperatures as high as 54°C (130°F), other deserts have cold winters or are cold year-round. And most deserts, far from being empty and lifeless, are home to a variety of plants, animals, and other organisms. People have adapted to life in the desert for thou sands of years.
- Overview
- Origin
desert, any large, extremely dry area of land with sparse vegetation. It is one of Earth’s major types of ecosystems, supporting a community of distinctive plants and animals specially adapted to the harsh environment. For a list of selected deserts of the world, see below.
Desert environments are so dry that they support only extremely sparse vegetation; trees are usually absent and, under normal climatic conditions, shrubs or herbaceous plants provide only very incomplete ground cover. Extreme aridity renders some deserts virtually devoid of plants; however, this barrenness is believed to be due in part to the effects of human disturbance, such as heavy grazing of cattle, on an already stressed environment.
The desert environments of the present are, in geologic terms, relatively recent in origin. They represent the most extreme result of the progressive cooling and consequent aridification of global climates during the Cenozoic Era (65.5 million years ago to the present), which also led to the development of savannas and scrublands in the less arid regions near the tropical and temperate margins of the developing deserts. It has been suggested that many typical modern desert plant families, particularly those with an Asian centre of diversity such as the chenopod and tamarisk families, first appeared in the Miocene (23 to 5.3 million years ago), evolving in the salty, drying environment of the disappearing Tethys Sea along what is now the Mediterranean–Central Asian axis.
Britannica Quiz
Ecosystems
Deserts also probably existed much earlier, during former periods of global arid climate in the lee of mountain ranges that sheltered them from rain or in the centre of extensive continental regions. However, this would have been primarily before the evolution of angiosperms (flowering plants, the group to which most present-day plants, including those of deserts, belong). Only a few primitive plants, which may have been part of the ancient desert vegetation, occur in present-day deserts. One example is the bizarre conifer relative welwitschia in the Namib Desert of southwestern Africa. Welwitschia has only two leaves, which are leathery, straplike organs that emanate from the middle of a massive, mainly subterranean woody stem. These leaves grow perpetually from their bases and erode progressively at their ends. This desert also harbours several other plants and animals peculiarly adapted to the arid environment, suggesting that it might have a longer continuous history of arid conditions than most other deserts.
Desert floras and faunas initially evolved from ancestors in moister habitats, an evolution that occurred independently on each continent. However, a significant degree of commonality exists among the plant families that dominate different desert vegetations. This is due in part to intrinsic physiologic characteristics in some widespread desert families that preadapt the plants to an arid environment; it also is a result of plant migration occurring through chance seed dispersal among desert regions.
Students save 67%! Learn more about our special academic rate today.
Former desert areas presently in non-arid environments, such as the Sandhills in Nebraska, are known as paleodeserts. In the Köppen climate classification system, deserts are classed as BWh (hot desert) or BWk (temperate desert).
Temperature. During the day, desert temperatures rise to an average of 38°C (a little over 100°F). At night, desert temperatures fall to an average of -3.9°C (about 25°F). Precipitation. Deserts get about 250 millimeters (10 inches) of rain per year—the least amount of rain of all of the biomes. Vegetation. Cacti, small bushes, short grasses.
Absolute minimum temperatures, except in desert areas close to the sea, are generally below the freezing point. Typical mean annual temperatures are between 20 °C (68 °F) and 25 °C (77 °F). Temperate or cold deserts occur
Sep 14, 2020 · Bactrian camels in the Gobi Desert. Temperate deserts, also known as cold deserts, occur at higher latitudes and therefore have cooler temperatures. Their aridity is caused by being far from the ocean or from being close to high mountains that prevent moist air from reaching inland. The largest temperate desert is the Gobi Desert of central ...
Sep 3, 2022 · A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation.
