This ecoregion is located in the Sahelian regional transition zone where high mountains rise from the low-lying semi-desert habitats. The height of these mountains creates an environment unlike that of the surrounding areas; here water is not scarce and sand does not dominate the soil structure. This isolated rugged habitat supports endemic plant and small animal species, and provides critical habitat for populations of some larger antelopes, such as the threatened addax (Addax nasomaculatus), dama gazelle (Gazella dama), dorcas gazelle (Gazella dorcas), and red-fronted gazelle (Gazella rufifrons).
Location and General Description
The largest portion of the East Saharan Montane Xeric Woodland ecoregion is located in Chad, where it encompasses the Massif Ennedi and Massif du Kapka at over 1,400 meters (m) elevation. A smaller outlier of this ecoregion is located in Sudan, the Jebel Marra, which reaches heights over 3,000 m. This ecoregion, comprised of two isolated areas, supports dry woodland vegetation surrounded by Sahel Acacia wooded grassland and deciduous bushland. Happold found that the high jebels, which support areas of moisture-dependent habitat instead of desert and semi-desert, are more likely to have a higher biodiversity value.
Throughout this ecoregion, most of the year's rainfall occurs between May and September. Precipitation varies greatly with elevation, ranging from 150 millimeters (mm) to 500 mm in most areas but reaching more than 1,000 mm on the higher parts of the Jebel Marra.
The Jebel Marra is volcanic in origin, with a relict crater now containing two lakes. Bare rock outcrops are found in many areas, although lithosols and yermosols also occur. While the Jebel Marra is comprised of Tertiary aged basalts, the upland Ennedi Plateau, above 1,800 m to 2,000 m, differs geologically by having a cap of Devonian-aged sandstone. Due to its huge size, the Jebel Marra offers multiple habitat types; valleys with deep litter soil and wooded forest, bare rocky outcrops, tall grass savanna, and a high elevation plateau of remnant volcanic ash with short grasses and wind blown bushes.
In terms of the phytogeograhical classification by White, this area is part of the Sahelian regional transition zone, which ranges between 1,800 m to 2,000 m. The actual vegetation of the ecoregion is mapped as Sahelomontane, one of three such areas in northern Africa. The flora has affinities to that of North Africa, the Ethiopian Highlands, the Kenyan Mountains, and Europe. Originally the higher elevation areas were probably dominated by Olea laperrinei (VU) scrub forest, however the current vegetation is dominated by secondary grassland, with O. laperrinei scattered across the landscape. On the steeper, more eroded slopes bunch grass and small shrub species like Andropogon distachyos, Themeda triandra, Hyparrhenia hirta, Lavandula pubescans and Blaeria spicata grow together. Areas with better drainage harbor a second type of grassland, including species like Hyparrhenia multiplex, Vulpia bromoides, Aristida congesta, Festuca abyssinica, Panicum pusillum, Tripogon leptophyllus and Pentaschistis pictigluma, all not more than 5 centimeters (cm) tall.
In terms of plants, a number of species endemic to the Sahel region occur in this ecoregion, including Ammannia gracilis, Chrozophora brocchiana, Farsetia stenoptera, Indigofera senegalensis, Launaea (Sonchus) chevalieri, Nymphoides ezannoi, Panicum laetum, Rotala pterocalyx, Tephorsia gracilipes, T. obcordata and T. quartiniana. Endemic lists from Wickens for the Jebel Marra Area include Gnaphalium marranum, Celsia sudanica, Kickxia aegyptiaca, K. dibolophylla, Pletranthus jebel-marrae, and Felicia dentata.
There are not many endemic animal species in this ecoregion. In mammals, the rat species Grammomys aridulus is near-endemic to the Jebel Marra portion of the ecoregion, and nearby lower areas. Two gerbils, Burton's gerbil (Gerbillus burtoni CR) and the hairy-footed gerbil (Gerbillus lowei CR), are both strictly endemic to the higher elevations of the Jebel Marra, with the latter confined to hillsides near the crater lakes. Both of these gerbils are regarded as critically endangered. The rusty lark (Mirafra rufa) is near-endemic to the area, also being found in other high altitude portions of the Sahara.
This ecoregion, particularly the Ennedi Plateau, is also an important location for larger mammals, including threatened antelope populations. Addax (Addax nasomaculatus CR), dama gazelle (Gazella dama EN), dorcas gazelle (Gazella dorcas VU), and red-fronted gazelle (Gazella rufifrons VU) are all found here. The greater kudu (Tragelaphus strepsiceros) is considered lower risk but in need of conservation assistance. The scimitar-horned oryx (Oryx dammah) is now considered extinct in the wild, but occurred in this ecoregion until the late 1980s. Although unlikely, it may be possible that a few survive on remote locations of the Ennedi Plateau. Other common species in this ecoregion include sand fox (Vulpes pallida), caracal (Caracal caracal), brown hare (Lepus capensis), rock hyrax (Procavia capensis), African wild cat (Felis silvestris), golden jackal (Canis aureus), and desert hedgehog (Hemiechinus aethiopicus).
The ecoregion includes elements of Afrotropical and Palearctic fauna, with key species including carrion eaters like Nubian buzzards (Neotis nuba) and black vultures (Aegypius monachus). Not many large predators exist in this ecoregion, except the endangered cheetah (Acinonyx jubatus). It also forms part of the greater Sahara ecosystem, where species have developed significant adaptations to drought. For example, dorcas gazelles may not drink water in their lifetime, receiving moisture solely from plants, while the Saharan cheetah can survive on the moisture acquired from the blood and urine of its prey.
The only habitats remaining undisturbed in this ecoregion are deep valley floors. However, these areas are inhospitable to larger vertebrates due to their small size and the steep sided valleys. The top of the Jebel Marra was once covered in scrub forest but is now secondary grassland with scattered trees due to human activities.
Humans have inhabited the Jebel Marra for over 2,000 years, with all accessible slopes up to 2,600 m elevation at one point used for agriculture.
Human activities are not believed to be currently threatening the habitats of this ecoregion, although recent reports are not readily available. Most of the agriculture once practiced in the area has been abandoned, resulting in regeneration of the landscape into more natural habitat (although not the original Olea laperrinei scrub forest type). This cannot be said of the fauna, as the larger animal species have been either removed or reduced to very small populations by hunting or competition with livestock and drought. One World Conservation Union (IUCN) category I-IV protected area the Fada Archei forest reserve in Chad also lies in part of this ecoregion. There is also a forest reserve in Sudan that covers part of the Jebel Marra area.
Types and Severity of Threats
The human population of the ecoregion is extremely low and mostly consists of nomadic and semi-nomadic people with a few farmers present in the valleys surrounding the ecoregion boundaries. The threats to the habitat are not believed to be very severe, but the threats to the remaining populations of large mammals from hunting are extremely serious. The habitat, however, could eventually be converted for agriculture as the human population continues to grow and demand for food within Chad and neighboring countries increases.
Justification of Ecoregion Delineation
The boundaries of the Massif Ennedi and Massif du Kapka in eastern Sahara were drawn around the 1,000 m elevation contour, while the boundaries for the Jebel Marra were taken directly from White. These high jebels, which contain moisture-dependent habitat, share as affinities areas in North Africa, the Ethiopian Highlands, Kenyan Mountains, and Europe.
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