Location and General Description
The Atlantic Coastal Desert comprises the westernmost portion of the Sahara, the world’s largest desert. This ecoregion covers the vast majority of Western Sahara’s 1,110 km coastline, from La'ayoune southwards, and roughly two-thirds of Mauritania’s 754 km of coastline. It includes Mauritania’s capital city of Nouakchott and the large port town of Nouadhibou to the northwest. It merges into the Mediterranean Acacia-Argania Dry Woodland to the north and is bordered to the west by the Northern Saharan Steppe and Woodland.
The ecoregion lies between sea level and a maximum of 200 m in elevation. Much of the coast is formed of cliffs 20 to 50 m high, and a sandy or gravelly hamada plateau stretches inland. The climate is extremely hot and arid, with only low amounts of episodic rainfall. Despite this, mists blown in from the Atlantic are common. Condensation of these mists permits the growth of lichens on shrubs and on the bare ground between vascular plants.
In terms of the phytogeographical classification of White (1983), this area is classified as part of the Sahara regional transition zone. The ecoregion has a much denser vegetation cover than that of other parts of the Sahara, and is also relatively rich in plant species. The Euphorbia-dominated succulent shrublands and the Argania spinosa scrub forests that characterize ecoregion 89 to the north essentially disappear at Seguia el Hamra (White 1983). However, some of the species of succulent shrubs have a scattered distribution in the northern part of this ecoregion, most notably Euphorbia regis-jubae, E. echinus, and Senecio anteuphorbium. In the south (i.e. coastal Mauritania), Sahelo-Saharan linked species such as Acacia tortilis, Maerua crassifolia, Salvadora persica, and Balanites aegyptiaca are well represented. Along the coast, halophytic species such as Suaeda, Atriplex, and Zygophyllum are common, together with plants such as Salsola longifolia, Heliotropium undulatum, and Lycium intricatum.
The human population density of the ecoregion is extremely low. The inhabitants traditionally practiced pastoral nomadism, raising camels, goats, and sheep. Now, more of the inhabitants that live close to the coast are engaged in the fishing industry. Others practice agriculture. Mining, working in towns, and in the oil industry are becoming increasingly important occupations.
The Atlantic Coastal Desert is relatively rich in endemic plants, but there are almost no endemic or near-endemic animals. One strictly endemic species is found in the ecoregion, the Algerian whip snake (Coluber algirus). Some of the more important biodiversity features are actually on the Atlantic Coast. The Mediterranean monk seal (Monachus monachus CR) (Hilton-Taylor 2000) has its last stronghold in the coves along the Cap Blanc Peninsula near the Mauritanian town of Nouadhibou on the border with Western Sahara.
The larger coastal bays, particularly the Baie d'Ad Dakhla and the Gulf of Cintra in Western Sahara and the Banc d'Arguin in Mauritania, are of immense importance for over two million wintering Western Palearctic waders, from fifteen different species (Shine et al. 2001). The most abundant are dunlin (Calidris alpina), bar-tailed godwit (Limosa lapponica), curlew sandpiper (Calidris ferruginea) and redshank (Tringa totanus) all with populations of over 100,000 birds (Dodman et al. 1997). Over one hundred thousand other waterbirds also use the wetlands for breeding or on migration, including more than 30,000 greater flamingos (Phoenicopterus ruber).
Notable terrestrial fauna include the Dorcas gazelle (Gazella dorcas VU), golden jackal (Canis aureus), fennec fox (Fennecus zerda), sand fox (Vulpes rueppelli), sand cat (Felis margarita), ratel (Mellivora capensis), and striped hyena (Hyaena hyaena LR/DD). The globally threatened dama gazelle (Gazella dama), addax (Addax nasomaculatus), and cheetah (Acinonyx jubatus) may have previously occurred here, but they are no longer found (East 1999).
The ecoregion is severely degraded due to prolonged droughts and overgrazing by livestock. However, little habitat has been totally lost because the arid climate prohibits farming, and thus extensive blocks of natural but degraded habitat remain throughout the ecoregion. There are only two existing protected areas, the 11,730 km2 Banc d'Arguin National Park and the 3,100 km2 Réserve Intégrale de Cap Blanc, both in Mauritania.
In addition, the coastal sector, called Aguerguer or Côte des Phoques, of the proposed 15,000- 20,000 km2 Parc National de Dakhla in Western Sahara will also include and protect a substantial part of this ecoregion.
Types and Severity of Threats
Overgrazing, cutting of trees for firewood and timber, and soil erosion aggravated by drought are contributing to desertification. The large mammal species have suffered from uncontrolled hunting, particularly by military personnel in Western Sahara. Invasion of brown rats (Rattus norvegicus) threatens seabird colonies along the coast. The population of monk seals is threatened by accidental capture and drowning in fishing gear, disturbance from tourists and fishermen, and the imminent danger of the collapse of their breeding caves due to coastal erosion. Wildlife in coastal areas is threatened by increasing pressure from the fishing industry and pollution from industrial developments at Nouâdhibou (Shine et al. 2001).
Justification of Ecoregion Delineation
The boundaries of this ecoregion, extending from the coast to 40 km inland, are taken directly from the ‘Atlantic coastal desert’ vegetation unit of White (1983). Its uniqueness derives from the mist it receives from the Atlantic making it relatively rich in endemic plants. It is also positioned along a major bird migration flyway. Thus, the few coastal wetlands within the ecoregion support huge bird populations, especially during the Palearctic winter months.
Dodman, T., C. de Vaan, E. Hubert, and C. Nivet. 1997. African waterfowl census 1997. Wetlands International, Waginingen.
East, R., editor. 1999. African Antelope Database 1998. IUCN/SSC Antelope Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. x + 434 pp.
Hilton-Taylor, C. 2000. 2000 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, United Kingdom.
Shine, T., Robertson, P. and Lamarche, B. 2001. Mauritania. In Fishpool, L. and Evans, M., editors. The Important Bird Areas of Africa. BirdLife International, Cambridge, UK.
White, F. 1983. The vegetation of Africa, a descriptive memoir to accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa (3 Plates, Northwestern Africa, Northeastern Africa, and Southern Africa, 1:5,000,000). UNESCO, Paris.
Prepared by: Chris Magin
Reviewed by: In progress