Sahara Desert (ecoregion)
Sand dunes in Tadrart Acacus a desert area in western Libya
|Biome||Deserts and xeric shrublands|
|Area||4,619,260 km2 (1,783,510 sq mi)|
|Countries||Algeria, Chad, Egypt, Libya, Mali, Mauritania and Niger|
|Rivers||Nile River; intermittent rivers and streams|
|Climate type||hyper-arid and subtropical|
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.
The Sahara is the world's largest hot desert, located in northern Africa. It stretches from the Red Sea to the Atlantic Ocean. The vast Sahara encompasses several ecologically distinct regions. The Sahara desert ecoregion covers an area of 4,619,260 km2 (1,783,510 sq mi) 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 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 (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.
The Sahara desert generally features an arid climate. The Sahara desert is one of the hottest regions of the world, with a mean temperature over 30 °C (86 °F). Daily variations may also be extreme: a swing from 37.5 to -0.5 °C (100 to 31 °F) has been observed. The Sahara receives very little rain in the Inter-Tropical Convergence Zone which moves up from the south. 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, such as the cheche worn by Tuareg.
History and conservation
The Sahara was one of the first regions of Africa to be farmed. Some 5,000 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: the Zellaf Nature Reserve in Libya.
- "Sahara Desert". Terrestrial Ecoregions. World Wildlife Fund. Retrieved 2011-03-21.