Ecoregions
The Sahara comprises several distinct ecoregions, and with their variations in temperature, rainfall, elevation, and soil, they harbor distinct communities of plants and animals.
The Atlantic coastal desert occupies a narrow strip along the Atlantic coast, where fog generated offshore by the cool Canary Current provides sufficient moisture to sustain a variety of lichens, succulents, and shrubs. It covers 39,900 square kilometers (15,400 sq mi) in Western Sahara and Mauritania.
The North Saharan steppe and woodlands lies along the northern desert, next to the Mediterranean forests, woodlands, and scrub ecoregions of the northern Maghreb and Cyrenaica. Winter rains sustain shrublands and dry woodlands that form a transition between the Mediterranean climate regions to the north and the hyper-arid Sahara proper to the south. It covers 1,675,300 square kilometers (646,800 sq mi) in Algeria, Egypt, Libya, Mauritania, Morocco, Tunisia, and Western Sahara.
The Sahara desert ecoregion covers the hyper-arid central portion of the Sahara where rainfall is minimal and sporadic. Vegetation is rare, and this ecoregion consists mostly of sand dunes (erg, chech, raoui), stone plateaus (hamadas), gravel plains (reg), dry valleys (wadis), and salt flats. It covers 4,639,900 square km (1,791,500 square miles) of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Niger, and Sudan.
The South Saharan steppe and woodlands ecoregion occupies a narrow band running east and west between the hyper-arid Sahara and the Sahel savannas to the south. Movements of the equatorial Intertropical Convergence Zone (ITCZ) bring summer rains during July and August which average 100 to 200 mm (3.9 to 7.9 in) but vary greatly from year to year. These rains sustain summer pastures of grasses and herbs, with dry woodlands and shrublands along seasonal watercourses. The ecoregion covers 1,101,700 km2 (425,400 mi2) in Algeria, Chad, Mali, Mauritania, and Sudan.
In the West Saharan montane xeric woodlands, several volcanic highlands provide a cooler, moister environment that supports Saharo-Mediterranean woodlands and shrublands. The ecoregion covers 258,100 km2 (99,700 mi2), mostly in the Tassili n'Ajjer of Algeria, with smaller enclaves in the Aïr of Niger, the Dhar Adrar of Mauritania, and the Adrar des Iforas of Mali and Algeria.
The Tibesti-Jebel Uweinat montane xeric woodlands ecoregion consists of the Tibesti and Jebel Uweinat highlands. Higher and more regular rainfall and cooler temperatures support woodlands and shrublands of palms, acacias, myrtle, oleander, tamarix, and several rare and endemic plants. The ecoregion covers 82,200 km2 (31,700 mi2) in the Tibesti of Chad and Libya, and Jebel Uweinat on the border of Egypt, Libya, and Sudan.
The Saharan halophytics is an area of seasonally flooded saline depressions which is home to halophytic, or salt-adapted, plant communities. The Saharan halophytics cover 54,000 km2 (20,800 mi2), including the Qattara and Siwa depressions in northern Egypt, the Tunisian salt lakes of central Tunisia, Chott Melghir in Algeria, and smaller areas of Algeria, Mauritania, and Western Sahara.
The Tanezrouft is one of the harshest regions on Earth and the driest in the Sahara, with no vegetation and very little life. It is situated along the borders of Algeria, Niger and Mali, west of the Hoggar mountains.
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