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Somali montane xeric woodlands

The Somali Montane Xeric Woodland ecoregion runs around the Horn of Africa, including a number of higher montane areas close to the sea. Although classified as part of the Somali-Masai regional center of endemism this area also contains remnant plant species linking it to Mediterranean, Macaronesian and Afromontane regions. It has served as a refuge for arid and semi-arid relict elements from these different regions. This ecoregion includes the highest point in Somalia and has the highest amount of rainfall in Somalia. At least ten species of plants, and six species of vertebrate animals are endemic to the ecoregion. The habitats are fairly intact due to the low human population and the inaccessibility of the escarpment and plateau areas, but populations of larger mammals have been greatly reduced by hunting. However, the difficult topography and long-running political problems mean that much of the region is unexplored biologically (WWF and IUCN 1994).

  • Scientific Code
    (AT1319)
  • Ecoregion Category
    Afrotropical
  • Size
    24,000 square miles
  • Status
    Critical/Endangered
  • Habitats

Description
Location and General Description
This ecoregion stretches along the coast of Somalia through the regions of Somaliland and Puntland from the Shimbiris Mountain east of Hargeysa through the northern mountains of Somalia to Raas Caseyr, covering the very tip of the Horn of Africa, and continuing some 300 kilometers south along the Somali coastal plain. Elevations range from sea level to the summit of Shimbiris at 2,416 m, the highest point in Somalia (WWF and IUCN 1994). There are also extensive coastal plains and sizeable mountain escarpments with areas higher than 1,500 m. As a result, some authorities (e.g. Friis 1992) consider these mountain areas to be biogeographic extensions of the Ethiopian highlands. The climate is hot and dry, with considerable seasonal temperature variations. Mean temperatures range from 21°C to 30°C in the lowlands to 9°C to 21°C in the mountains. The mean rainfall of the low-lying areas is less than 200 mm annually, though it is presumably far greater at higher elevations, and falls mainly during the winter months. The escarpment near Maydh receives the most rainfall in Somalia, over 700 mm each year.

Most of the higher mountain areas are composed of limestone and gypsum, covered with free-draining thin rendzina lithosols that retain little moisture outside the rainy seasons. Many endemic species are confined to these areas, such as Reseda sessilifolia that grows on outcrops of gypsum.

The vegetation of this ecoregion varies due to elevation, rainfall, and soil or rock types. At lower elevations, xerosols and yermosols have developed, particularly on the lowland coastal plains bordering the Indian Ocean. Here, there is little to no vegetation in this desert to semi-desert habitat. In subcoastal areas woody vegetation becomes denser with dominant species from the genera Acacia, Commiphora, and Boswellia (WWF and IUCN 1994). Along the sides of the escarpment Macchia-like evergreen and semi-evergreen scrub occurs with species such as Dracaena schizantha, Cadia purpea, Buxus hildebrandtii, and Pistacia aethiopica, while remnants of Juniperus forest grow at higher altitudes on the mountains (WWF and IUCN 1994, White 1983).

Biodiversity Features
The biological value of the ecoregion is poorly known. Most of the area has been inaccessible for many years due to political instability in Somalia, and much of the information that does exist is old and potentially unreliable. However, it is known that there are over ten species of endemic plants represented in this ecoregion, including relict elements of arid and semi-arid groups; for example, four endemic species of Helianthemum and one endemic species of Thamnosma. Also, the monotypic genus Renschia is a strict endemic (WWF and IUCN 1994). Both WWF and IUCN (WWF and IUCN 1994), Friis (1992) and Lovett and Friis (1996) regard this as a center of endemism for plants. The most endemic-rich zone is the high montane region, but plant endemics are also found at lower elevations.

There are three strict endemic reptiles, the snakes Spalerosophis josephscorteccii and Leptotyphlops reticulatus and the lizard Pseuderemias savagei, with two other reptiles nearly-endemic to the ecoregion. Three strict endemic birds also occur: the Somali pigeon (Columba oliviae, DD), the Somali thrush (Turdus ludoviciae, CR), and the Warsangli linnet (Carduelis johannis, EN), all found in the North Somali mountains endemic bird area (Stattersfield et al. 1998). Three small mammal species are also considered near-endemics, Atelerix sclateri, Acomys louisae and Elephantulus revoili. The rare antelopes beira (Dorcatragus megalotis, VU) and Speke's gazelle (Gazella spekei, VU) are also found here and in a few other ecoregions in the Horn of Africa area (East 1999).

The severely threatened Somali thrush and Warsangli linnet are principally or perhaps wholly confined to juniper forests at higher elevations. More widely distributed mammal species such as Speke's gazelle (Gazella spekei, VU), Salt’s dikdik (Madoqua saltiana), beira (Dorcatragus megalotis, VU), and Soemmerring's gazelle (Gazella soemmerringii, VU) are also threatened and suffer from over-hunting and from grazing competition with livestock (East 1999).

Current Status
Due to the longstanding and continued political difficulties in the former Somalia, there is no accurate information about the habitat within this ecoregion. It is known that the area of juniper forest has been greatly reduced and what remains is heavily degraded. At lower elevations and drier sites, the vegetation may be in better condition because the human population density is low and the habitats are semi-deserts in many areas. Previously, small forest patches were principally centered on the higher elevation areas of the Surud-Ad-Al Madu and Mosca highlands (Friis 1992). The only protected areas within the ecoregion are a few forest reserves, of which the most important is Daloh Forest Reserve, an area of montane Juniperus forest. Because of the past political situation these areas probably have not been protected for some time.

Types and Severity of Threats
The major threats to the ecoregion are thought to be intensive grazing by goats and other livestock (including cattle in the mountains), and cutting of Juniperus trees for timber and fuel wood. Hunting of larger mammals is also a long-standing problem. The prolonged period of political instability in the ecoregion may have also resulted in a number of additional threats, but apart from the breakdown of management authorities set up to conserve forests and wildlife, these are not well documented.

Justification of Ecoregion Delineation
This ecoregion follows the ‘Somalia-Masai semi-desert grassland and shrubland’ vegetation unit classified by White (1983). The Somali Montane Xeric Woodland covers approximately the same area as the North Somali Mountains Endemic Bird Area (Stattersfield et al. 1998), and includes Cal Madow (Al Medu), a center of endemism for plants (WWF and IUCN 1994). It also shares affinities with the Mediterranean, Macaronesian and Afromontane regions. Modifications to the ecoregion include its extension further west than Berbera, as well as the inclusion of the littoral region and an island of montane vegetation at Shimbiris, east of the Harer branch of the Ethiopian Highlands (WWF 1998). Although White (1983) classifies this unit with the Ethiopian Highlands, it was considered to be more similar to the other parts of the Somalian Xeric Woodland ecoregion.

References
East, R. (comp.) 1999. African Antelope Database 1998. IUCN/SSC Antelope Specialist Group. ICN, Gland, Switzerland and Cambridge, UK. x + 434 pp.

Friis, I. 1992. Forests and Forest Trees of Northeast Tropical Africa. HMSO, Kew Bulletin Additional Series XV.

Lovett, J.C., and I. Friis. 1996. Patterns of endemism in the woody flora of north-east and east Africa. Pp. 582-601. In: L.J.G. van der Maesen et al. (eds.). The Biodiversity of African Plants. The Netherlands: Kluwer Academic Publishers.

Stattersfield, A.J., M.J. Crosby, A.J. Long, & D.C. Wege. 1998. Endemic Bird Areas of the World. Priorities for Biodiversity Conservation. BirdLife Conservation Series No. 7. BirdLife International, Cambridge, UK. 846 pp.

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.

WWF and IUCN. 1994. Centres of plant diversity. A guide and strategy for their conservation. Volume 1. Europe, Africa, South West Asia and the Middle East. IUCN Publications Unit, Cambridge, U.K.

WWF. 1998. A conservation assessment of terrestrial ecoregions of Africa: Draft proceedings of a workshop, Cape Town, South Africa, August 1998. World Wildlife Fund, Washington, DC, USA.

Prepared by: Chris Magin, Christine Burdette
Reviewed by: In progress

 

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