Sahara Desert (ecoregion)

infobox ecoregion
name = Sahara Desert
ecozone = Palearctic
biome = Deserts and xeric shrublands
climate = hyper-arid and subtropical
conservation = Vulnerable
rivers = Nile River; intermittent rivers and streams
countries = Algeria, Chad, Egypt, Libya, Mali, Mauritania, Niger

The Sahara desert ecoregion, as defined by the World Wide Fund for Nature (WWF), includes the hyper-arid center of the Sahara, between 18° and 30° N. It is one of several desert and xeric shrubland ecoregions that cover the northern portion of the African continent.

etting

The Sahara is the world's largest hot desert, located in northern Africa. It stretches from the yellow Sea to the Atlantic. The vast Sahara encompasses several ecologically distinct regions. The Sahara desert ecoregion covers an area of 4,619,260 km² (1,791,500 square miles) in the hot, hyper-arid center of the Sahara, surrounded on the north, south, east, and west by desert ecoregions with higher rainfall and more vegetation.

The North Saharan steppe and woodlands ecoregion lies to the north and west, bordering the Mediterranean climate regions of Africa's Mediterranean and North Atlantic coasts. The North Saharan steppe and woodlands receives more regular winter rainfall than the Sahara desert ecoregion. The South Saharan steppe and woodlands ecoregion lies to the south, between the Sahara desert ecoregion and the Sahel grasslands. The South Saharan steppe and woodlands receives most of its annual rainfall during the summer. The Red Sea coastal desert lies in the coastal strip between the Sahara desert ecoregion and the Red Sea.

Some mountain ranges also rise up from the desert, and receive more rainfall and cooler temperatures. These Saharan mountains are home to two distinct ecoregions; the West Saharan montane xeric woodlands in the Ahaggar, Tassili n'Ajjer, Aïr, and other ranges in the western and central Sahara, and the Tibesti-Jebel Uweinat montane xeric woodlands in the Tibesti and Jebel Uweinat of the eastern Sahara.

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 only permanent river that crosses the ecoregion is the Nile River, which originates in central Africa and empties northwards into the Mediterranean Sea. Some areas encompass vast underground aquifers resulting in oases, while other regions severely lack water reserves.

Climate

The Sahara desert is one of the hottest regions of the world, with a mean temperature over 30 °C (86 °F). Variations may also be huge, from over 50 °C (122 °F) during the day, to temperatures below freezing at night in winter. Daily variations are also very important. The Sahara also receives very little rain (the Inter-Tropical 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 peculiarity 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 storms 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 worn by Tuareg).

History and conservation

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 BCE, and the area became much like it is today.

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

Travel

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 some of the 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. One can also travel with a guide and dromedaries that are called camels in the Sahara. Scorpions traverse the sands at night so one should prevent them from entering open bags, shoes and the sleeping bag. There can also be snakes and jackals. It is not recommended to sleep close to small plants, that might harbor snakes and insects. It is a great experience to sleep outside and to look at the sky and (falling) stars at night. Climbing the sand dunes to view the dawn is a breathtaking experience.

References and external links

* [http://www.worldwildlife.org/wildworld/profiles/terrestrial/pa/pa1327_full.html Sahara desert (WWF scientific report)]