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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

531: Shebelle - Juba

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Abebe Getahun, Department of Biology, Addis Ababa University, Addis Ababa, Ethiopia

Countries:

Ethiopia; Kenya; Somalia

Boundaries:

The xeric systems of this ecoregion include the Wabi Shebelle and Juba basins with the ecoregion extending from Kenya to Somalia along the coast of the Indian Ocean and inland to the Ethiopian Highlands [525]. During flooding, the rivers often spill over their banks and inundate adjacent floodplains.

Climate:

All of the lower Wabi Shebelle and adjacent areas are very dry. The most reliable month for rain is April, followed by May, whereas no rain falls between October and September (Ethiopian Wildlife and Natural History Society 1996). The hottest months are February and March.

Freshwater habitats:

Draining from the southeastern escarpment of the eastern Ethiopian highlands, the Wabi Shebelle and the Fafan Rivers flow through the Somalian desert, although they do not reach the Indian Ocean. The Wabi Shebelle is the major river of the central Somali region. Rising between the Arsi and Bale Mountains, it flows in a southeasterly direction to Somalia. In its lower section, the Wabi Shebelle and its main seasonal tributary from the east, the Fafan, cut through a series of wide, flat shelves of sedimentary rocks made of sandstone, limestone, and gypsum. Wabi Shebelle, with a catchment area of 205,407 km2, winds a length of 1340 km inside Ethiopia, and a further 660 km in Somalia (Ethiopian Mapping Authority 1988). The Wabi Gestro, the Ghenale River, and the Dawa Parma River drain the southwestern escarpment of the eastern Ethiopian highlands. These rivers unite and become the Juba River, which eventually drains into the Indian Ocean (Westphal 1975). These Juba tributaries arise just east of Abaya and Chamo Lakes, but are separated from the lake drainages by a high mountainous divide. According to Roberts (1975), midway between the lower courses of the Wabi Shebelle and the Juba there is a low-lying limestone plateau with extensive underground waterways radiating out from it.

Terrestrial Habitats:

Floodplains are often covered in a tangled growth of small bushes and herbs, which include wild relatives of cotton. Large trees are not naturally found on the floodplains, but heat-tolerant species, including Hyphaene thebaica, have been planted in settlements (Ethiopian Wildlife and Natural History Society 1996).

Fish Fauna:

The rivers in this ecoregion are believed to host many Nilo-Sudanic fishes similar to the southern rift valley lakes (Lakes Chamo and Abaya). It is believed that these lakes and the Shebelle-Ghenale River basins had former connections with the upper White Nile as recently as 7,500 years ago (Roberts 1975; McClanahan & Young 1996). Some of the rivers in this ecoregion (e.g., Ghenale River) support abundant populations of fish. For example, Woldemariam (1972) in Tedla (1973) exaggerated that it is difficult to take a bath in the river because of the high numbers of the fish(Tedla 1973).

Description of endemic fishes:

Endemic fish, including Bagrus urostigma, Labeo boulengeri, Labeo bottegi, and Synodontis geledensis, live in the rivers of this ecoregion. Most of the Nilotic species found in Lake Abaya, with the exception of Hyperopisus bebe, are also present in the Wabi Shebelle-Juba drainage (Roberts 1975). Another important feature of the area is the presence of subterranean waterways, which are inhabited by the endemic monotypic fish genera Uegitglanis and Phreatichthys. Both the clariid catfish (U. zammaranoi)and the cyprinid (P. andruzzii)lack visible eyes and are depigmented and scaleless.

Other noteworthy aquatic biotic elements:

The vegetation alongside the middle section of the Ghenale River also supports populations of the vulnerable Prince Ruspoli’s turaco (Tauraco ruspolii),white-winged collared-dove (Streptopelia reichenowi), and Jubaland weaver (Ploceus dicrocephalus) (Ethiopian Wildlife and Natural History Society 1996, 2001). Along the coast in Somalia are several areas of importance for waterbirds, for example the Jasiira lagoon is known to support congregations of Phoenicopterus ruber and Egretta gularis (Robertson 2001).

Ecological phenomena:

A continuous escarpment, running in a wide curve from the Kenyan border to northern Somalia, forms the western and northern borders of this ecoregion, while the southwestern part of this escarpment forms the eastern wall of the Rift Valley. The escarpment rises northwards and attains its maximum elevation of over 3,000m near the Chilalo Massif in Ethiopia. Several endemic fishes live in the streams and subterranean waters of this xeric ecoregion.

Justification for delineation:

A continuous escarpment, running in a wide curve from the Kenyan border to northern Somalia, forms the western and northern borders of this ecoregion, while the southwestern part of this escarpment forms the eastern wall of the Rift Valley. The escarpment rises northwards and attains its maximum elevation of over 3,000m near the Chilalo Massif in Ethiopia. Several endemic fishes live in the streams and subterranean waters of this xeric ecoregion

Level of taxonomic exploration:

Poor. The native freshwater flora and fauna of this vast ecoregion has been poorly investigated. Although the riparian vegetation has been described to some extent, little is known about the upland vegetation. Without better information, identification of conservation priorities is difficult.

References/sources:

McClanahan, T. R.,Young, T. P. (1996) East African ecosystems and their conservation. New York, USA: Oxford University Press.

Roberts, T. R. (1975). "Geographical distribution of African freshwater fishes" Zool. J. Linn. Soc. 57 249-319.

Robertson, P. (2001)"Somalia" In Fishpool, L.D.C.;Evans, M.I. (Ed.). Important bird areas in Africa and associated islands: Priority sites for conservation. (pp. 779-792) Newbury and Cambridge, UK: Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11).

Tedla, S. (1973). "Freshwater Fishes of Ethiopia" Unpublished Thesis. Dept. of Biology, Haile Selassie I University.

Westphal, E. (1975). "Agriculture systems in Ethiopia. Joint publication of the College of Agriculture, Haile Selassie I University, Ethiopia and the Agricultural University, Wageningen, The Netherlands"

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