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Sahara Desert (ecoregion)

From Academic Kids

The Sahara Desert is an ecoregion covering part of the Sahara.

The Sahara is the world's second largest desert (Antarctica is the largest) and is located in northern Africa. It stretches from the Red Sea to the highlands of Ethiopia. However, the Sahara encompasses regions significantly different from an ecological perspective. The surface of the desert ranges from large areas of sand dunes (which are called erg), to stone plateaus (hamadas), gravel plains (reg), dry valleys (wadis), and salt flats. The northern and southern margins also receive more rainfall and have greater vegetation than central Sahara. The very scarse rain (less than 25 mm and even less than 5 mm per annum in the east) can fall in any season and in a very irregular way : some areas may receive no rain for years then suffer intense storms. Some areas encompass vast underground aquifers resulting in oases, while other regions severely lack water reserves. Some mountains (Ahaggar, Tassili NAjier, Tibesti, Ar) also rise up in the desert and receive more rainfall and mostly present slightly cooler summer temperatures.

For such reasons, the great Sahara may be divided in several ecoregions and each of them be separately described. Other ecoregions are

Contents

Overview

This ecoregion covers the central Sahara Desert, between 18 and 30 N, and has an area of 4,619,260 km² (1,791,500 square miles)

Ecozone : Palearctic
Biome : Deserts and xeric shrublands
Climate type : extreme in the dry and hot climate
Soil types :
Conservation status : Vulnerable
Oceans or seas (borders) : from the Atlantic Ocean to the Red Sea
Rivers :
Countries :

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The Sahara desert is one of the hottest regions of the world, with a mean temperature over 30C. Variations may also be huge, from over 50C during the day, to freezing temperatures at night in winter. Daily variations are also very important. The Sahara also receive very little rain (the Intercontinental Convergence Zone moves up from the south, but stops before the center of the Sahara while the winter rainfall of North Africa does not reach far south enough to regularly bring rain to the central Sahara). Not only scarce, the rain is also extremely irregular. Each rainfall is followed by a major vegetation growth and blooming. Another pecularity of the desert is the presence of wind. Small and hot dust-filled winds creating dust devils are observed and full-blown wind and sand storm occur as soon as early spring. Local inhabitants protect themselves from heat, cold and mostly wind and sand by covering their heads (see the cheche wore by Tuareg).

The Sahara was one of the first regions of Africa to be farmed. Some 5000 years ago, the area was not so arid and the vegetation might have been closer to a savanna. Previous fauna may be recognised in stone carvings.

However, desertification set in around 3000 BC. Some historians and anthropologists have suggested that over-grazing by the domestic animals (particularly pigs) of ancient civilizations of the region was a primary factor in its eventual desertification. The Sahara is largely undisturbed. The most degradation is found in areas where there is water, such as aquifer oases or along the desert margins where some rain usually falls most years. In these areas, animals such as addaxes, scimitar-horned oryxes, and bustards are over-hunted for their meat.

The southern border of the Sahara is marked by the Sahel.

Only one area of conservation is recorded in the Sahara: Zellaf Nature Reserve in Libya (1000 km²) (WCMC 2000).

Appearance

A relatively convenient way to approach the scenery of the heart of the Sahara is through Morocco. From Marrakesh or Fez one climbs up over the High Atlas Mountains and thereupon enters the desert. Heading into the desert one notices the size of the boulders becomes progressively smaller; to begin with they are huge. As they miles go by the boulders become smaller and smaller until about fifty miles in they become sand. The towns such as Ouarzazat, and villages become progressively smaller until finally one reaches the sand dunes. The roads become progressively narrower until they are just paths between the pebbles. Past traffic tends to wear the paths into a regular series of ruts, akin to a washboard, so travel is bumpy. This washboard effect coupled with the sand places considerable strain on vehicles. Taking considerable supplies of water is strictly necessary, along with shade, a local guide and a second vehicle for safety. Scorpions traverse the sands at night so it is not really safe to sleep outside. Climbing the sand dunes to view the dawn is a breathtaking and memorable experience.

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