Sahara desert (ecoregion)
The Sahara Desert
is the world's largest hot, non-polar desert and is located in North Africa
. It stretches from the Red Sea
to the Atlantic Ocean
. The vast desert 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 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 east 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 features a hot desert climate
(Köppen climate classification BWh
). The Sahara Desert is one of the driest and hottest regions of the world, with a mean temperature sometimes over 30 °C (86 °F) and the average high temperatures in summer are over 40 °C (104 °F) for months at a time, and can even soar to 47 °C (117 °F). In desert rocky mountains such as the Tibesti
in Libya or the Hoggar
in Algeria, average highs in summer are slightly moderated by the high elevation and are between 35 and 42 °C (95 and 108 °F) at 1,000 to 1,500 metres (3,300 to 4,900 ft) elevation. Daily variations may also be extreme: a swing from 37.5 to −0.5 °C (100 to 31 °F) has been observed.
Typical temperature swings are between 15 and 20 °C (27 and 36 °F).
Precipitation in the Sahara Desert is scarce, as the whole desert generally receives less than 100 millimetres (3.9 in) of rain per year except on the northernmost and southernmost edge as well as in the highest desert mountains. More than half of the desert area is hyper-arid and virtually rainless, with an average annual precipitation below 50 millimetres (2.0 in) and many consecutive years may pass without any rainfall. The south of the Sahara Desert, along the boundary with the hot semi-arid climate
) of the Sahel
, receives most of its annual rainfall during the highest-sun months (summer) when the Inter-Tropical Convergence Zone
moves up from the south. Wind-
occur in early spring. Local inhabitants protect themselves from the heat, the sunshine, the dry air, the high diurnal temperature ranges and the sometimes dusty or sandy winds by covering their heads, such as the cheche
garment worn by Tuareg
History and conservation
Addaxes grazing in a deserted region
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
for their meat. Only one area of conservation
is recorded in the Sahara: the Zellaf Nature Reserve in Libya.
In 2001, WWF devised Terrestrial Ecoregions of the World (TEOW) "a biogeographic regionalization of the Earth's terrestrial biodiversity".
The 2001 regionalization divided the deserts of the Sahara into several ecoregions. The Sahara desert ecoregion included the Sahara's hyper-arid center, and the more humid Saharan mountains and southern, northern, eastern, and western deserts were separate ecoregions.
- ^ a b c d e f g "Sahara Desert". Terrestrial Ecoregions. World Wildlife Fund. Retrieved 2011-03-21.
- ^ "Terrestrial Ecoregions of the World". World Wildlife Fund. Accessed 25 April 2020. 
- ^ Olson, D. M., Dinerstein, E., Wikramanayake, E. D., Burgess, N. D., Powell, G. V. N., Underwood, E. C., D'Amico, J. A., Itoua, I., Strand, H. E., Morrison, J. C., Loucks, C. J., Allnutt, T. F., Ricketts, T. H., Kura, Y., Lamoreux, J. F., Wettengel, W. W., Hedao, P., Kassem, K. R. 2001. Terrestrial ecoregions of the world: a new map of life on Earth. Bioscience 51(11):933-938.
- ^ Eric Dinerstein, David Olson, et al. (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm, BioScience, Volume 67, Issue 6, June 2017, Pages 534–545, 
Last edited on 11 May 2021, at 12:17
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