West Saharan montane xeric woodlands

The West Saharan montane xeric woodlands is an ecoregion that extends across several highland regions in the Sahara. Surrounded at lower elevations by the largely barren Sahara, the West Saharan montane xeric woodlands are isolated refuges of plants and animals that can survive in the higher humidity and lower temperatures of the highlands.

Setting

The Sahara is vast desert, stretching across northern Africa from the Atlantic Ocean to the Red Sea. Some mountains (Ahaggar, Tassili n'Ajjer, Tibesti, Aïr) rise up from the desert and receive more rainfall and mostly present slightly cooler summer temperatures. These highlands support dry woodlands and shrublands distinct from the hot dry desert lowlands.

This ecoregion has an area of 258,100 km² (99,700 square miles). The boundaries for the largest part of this ecoregion, which includes the Tassili-n-Ajjer Ahaggar and Aïr (or Azbine) massifs, follow the 'regs,' 'hamadas' and 'wadis' above the 1000 m contour. This covers a good part of southeast Algeria. These areas reach almost 3000 meters in altitude. Additional areas further south were included within this ecoregion, including the Aïr ou Azbine in northern Niger, Dhar Adrar in Mauritania, and Adrar des Iforas in Mali and Algeria, using the 500 m-elevation contour.

The mountains of the West Saharan Montane Xeric Woodland ecoregion are found within the Sahara Desert and are predominantly of volcanic origin. They rise from the surrounding flat desert landscape or sand dunes and create islands of moister habitat (guelta) which support flora and fauna. The most important area is the Tassili-n-Ajjer Plateau, an outlier of the Ahaggar Mountains in Algeria which supports some near-endemic species and some globally threatened antelopes. The highest point of these mountains is 3003 meters (Mount Tahat).

Winters are quite rigorous, with amplitude in temperature over 20°C. Day temperatures may be over 20°C while nights are freezing. In summer, days are very hot, though less than in central Sahara. Rainfall is rare and sporadic.

Flora and fauna

Vegetation varies greatly depending on altitude and landscape (in particular wind protection). It is often relict of mediterranean vegetation.

In gueltas, vegetation is very diverse and hosts many animals. Trees may be found at lower elevations, while higher mostly host bushes. It is however possible to find olive trees (the olive tree on the right hand picture was found at 2300 m). Endemic and rare species includes Saharan Cypress (“tarout”) (Cupressus dupreziana), wild olive (Olea lapperrini) and Saharan Myrtle (Myrtus nivellei), all of which are relict Saharan-Mediterranean species. Olive and myrtle trees grow at the bottom of wadis, intermittent stream valleys, or beside gueltas, permanent or temporary waterholes.

Other species with a preference for moist habitats are Trianthema pentandra, Lupinus pilosus, and Convolvulus fatmensis. Silene kiliani, Acacia laeta, A. scorpiodes, and Cordia rochii grow in wadis. Other representatives of the 28 national Algerian plant rarities found on Tassili-n-Ajjer include Ficus ingens and Anticharis glandulosa.

Population and conservation

The human population of the ecoregion is very small, with less than 5 persons per km². Many people are nomadic though some small cities also exist (ideles). The vegetation remains fairly intact.

References and external links

• West Saharan montane xeric woodlands (World Wildlife Fund)