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Learn about the different types, causes, and features of deserts, the arid ecosystems that receive very little precipitation. Explore the diversity and adaptations of plants and animals that live in deserts around the world.
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the land surface of the Earth is arid or semi-arid.
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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.
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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.
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Learn about desert, a large, extremely dry area of land with sparse vegetation and distinctive plants and animals. Explore the origin, distribution, and diversity of deserts around the world.
Oct 19, 2023 · Learn about the characteristics, types, and adaptations of deserts, the extremely dry environments that cover one-fifth of Earth's surface. Explore the examples of arid, semi-arid, coastal, and cold deserts with images and vocabulary.
Oct 19, 2023 · Learn about the types, features, and challenges of deserts, the biologically rich habitats that cover one-fifth of Earth's land area. Find out how deserts are affected by climate change, human activities, and conservation efforts.
Jun 28, 2019 · National Geographic. 23.1M subscribers. Subscribed. 12K. 1.4M views 4 years ago #NationalGeographic #Deserts #Educational. Deserts are diverse ecosystems that occur on all seven continents....
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Learn about the diversity, adaptations, and threats of deserts, the biologically rich habitats that cover one-fifth of the Earth's land area. Find out how deserts are affected by climate change, land use, and human activities.
