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| Sunday, 13 February 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Deserts where the earth has gone dry
They are usually very dry. Even the wettest deserts get less than ten inches of rainfall a year. In most other places of the earth, rain falls steadily throughout the year. But in the desert, there may be only a few periods of rain per year which may be rather brief with long dry periods in between. It may be known to you that many deserts are hot during the day with temperatures sometimes exceeding 100 degrees Fahrenheit. During the night the same deserts can have temperatures falling into the range of 40 or 50 degrees Fahrenheit. Why does this happen? Other biomes are insulated by their humidity (water vapour in the air). Temperate deciduous (trees which periodically shed leaves) forests, for example, may have above 80 per cent humidity during the day. This water reflects and absorbs the sunlight and the energy it brings. At night, the water acts like a blanket, trapping heat inside the forest. Since deserts usually have only between 10 and 20 per cent humidity to trap temperatures and have so few trees and other vegetation to retain heat, they cool down rapidly when the sun sets, and heat up quickly after the sun rises. There are two types of deserts in the world: cold deserts and hot deserts. Snow is the main form of precipitation (moisture) in a cold desert where the annual rainfall is less than ten inches. The main form of precipitation in a hot desert is rain; but that's only ten inches or less of rain per year. Many deserts are found within the band between 30 degrees latitude North and 30 degrees latitude South. Some deserts are located beside mountains and are caused by the "rainshadow" effect. As air moves up over a mountain range, it gets cold and loses the ability to hold moisture - so it rains or snows. When the air moves down the other side of the mountain, it gets warmer. Warm air can hold lots of moisture, so it doesn't rain as much, and a desert is formed. Although deserts are harsh and dry, they are home to many living things. In fact, deserts are second only to tropical rainforests in the variety of plant and animal species that live there. How do you think plants grow in soil which is extremely dry? Many of the fascinating features of desert plants are adaptations - traits that help the plant survive in its harsh environment. Desert plants have two main adaptations: the ability to collect and store water, and features that reduce water loss. Desert plants often look different from plants in other biomes. Animals in the desert must survive in a hostile environment. Intense heat, searing sun, and lack of water are just a few of the challenges facing desert animals. Animals that live in the desert have adaptated in many ways to their harsh surroundings. Some animals never drink, but get their water from seeds (some seeds contain upto 50 per cent water) and plants. Many animals are nocturnal, sleeping during the hot day and only coming out at night to hunt and eat. Some animals rarely spend any time above ground. Spadefoot toads spend nine months of every year underground! Eucalyptus, saltbush, spinifex grass, blue-tongued lizard, dingo, fat-tailed mouse, kangaroo, marsupial mole, rabbit-eared bandicoot, sand goanna, spinifex hopping mouse and thorny devil are some examples of animals living in deserts. And did you know that Aborigines lived in the Australian deserts for over 30,000 years? The biggest desert in the world is Northern Africa's Sahara Desert; it covers 3,500,000 square miles (9,065,000 square kilometres). The driest deserts are the Atacama of Northern Chile, South America, and the Lut in Eastern Iran; these deserts get less than half an inch (about 1 centimetre) of precipitation each year - and it is from condensed fog, and not rain. ######### Cold deserts of the world The Atacama, located in the coasts of Peru and Chile, is considered as one of the driest areas on earth. Atacama is covered by sand dunes and pebbles. Bunchgrass, cardon cactus, tamaruga trees, lizards, llama and Peruvian fox are some of the animals and plants found here. The desert also provides a nesting area for many seabirds. Large deposits of sodium nitrate, used to make gun powder, are found in this desert. The Gobi desert situated between Northern China and Southern Mongolia is covered by sandy soil, and areas of small stones which are called "gobi". Camel's thorn, grasses, gazelle, gerbil, jerboa, lizards, onager, and wolves are some of the plants and animals living in the Gobi desert. Hot deserts of the world The Arabian Desert located in the Arabian Peninsula is covered almost entirely by sand. It has some of the most extensive stretches of sand dunes in the world. Acacia, oleander, saltbush, desert locust, dromedary camel (camel with one hump), gazelle, lizard, jackal and oryx are some plants and animals found in the Arabian Desert.The Australian deserts of Great Sandy, Victoria and Simpson are sandy, while Gibson and Sturt are stony. |
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Did you know that deserts cover about one fifth (20 per cent) of the
earth's land area? The desert is a harsh environment with very little
rainfall and extreme temperatures.
