Contact Us|Site Map


Ecoregion Description


View global map

Species Richness


# of Endemic Species


Threats

536: Uele

Major Habitat Type:

tropical and subtropical upland rivers

Author:

Emily Peck, WWF-US, Conservation Science Program, Washington, DC, USA

Reviewers:

Luc De Vos, National Museum of Kenya, Nairobi, Kenya

Countries:

Central African Republic; Democratic Republic of Congo

Boundaries:

The rivers and streams within the Uele ecoregion drain from a high plateau along the northeastern border of the Congo basin in the Democratic Republic of Congo. The basin of the Uele River, a major tributary to the Ubangui, determines the boundaries of this ecoregion.

Main rivers or other water bodies:

The Uele River and its affluents, the Bili, Uere, and Bomokandi Rivers, drain woodland savannas in the north and east and mixed evergreen forests in the south and west. The Uele River begins in the Blue Mountains at an elevation of 1620 m, and then traverses the high plateau for 1170 km before joining the Ubangui River in Yakoma, below 500 m (Orange 1998). The Uele River’s catchment covers 139,700 km². The Bili is a blackwater river with a catchment area of 27,400 km². The Bili runs through more extensive areas of evergreen forests and carries a large amount of dissolved organic matter (Orange 1998).

Topography:

The high plateau in the northeast of the ecoregion slopes west and south toward the central Congo basin. Numerous scarps and cliff faces break up the gently sloping landscape. As a result, waterfalls and rapids mark all rivers running off the plateau toward the central Congo basin. 

Climate:

The Uele ecoregion is situated between 3-5º N. Rainfall varies from west to east and seasonally. The lower elevation, more densely forested western part of the ecoregion receives an average annual rainfall of 1600-1700 mm. The higher, savanna-covered eastern plateau experiences an average annual rainfall of 1200-1500 mm. The wet season usually extends from March to November, and the dry season from December to February. The mean annual temperature for the ecoregion is 24ºC (WCMC 1984; Orange 1998).

Terrestrial Habitats:

A mosaic of afromontane forest, gallery forest, wooded savanna, and grassland blankets the northern highlands of the Uele ecoregion. Savannas range from dense woodland to virtually treeless grassland. Loudetia arundinacea and Hyparrhenia spp. dominate the grasslands of the far northeast. Numerous small rivers and papyrus swamps dissect these grasslands. Combretum spp. and Terminalia spp. dominate the savanna woodland vegetation. Other predominant species include Bauhinia thonningii, Dombeya quinqueseta, Hymenocardia acida and Acacia, Grewia and Bridelia spp. Gallery forest contains Irvingia smithii, Erythrophleum suaveolens, Chlorophora excelsa, and Klainedoxa and Ficus spp. (WCMC 1984). 

The montane forests of the Blue Mountains exhibit an altitudinal zonation of plant species. Species such as Podocarpus, Prunus, and Ocotea occur at intermediate elevations. At higher altitudes these forests transition to elfin forests and communities of bamboo, tree ferns, and lobelias. At the highest altitudes, afro-alpine moorlands occur with a variety of shrubs and grasses (Sayer et al. 1992). Fire plays an important role in the maintenance of the vegetation cover and often sweeps across the savanna during the dry season. In the southern and western parts of the ecoregion, a closed canopy of broadleaf and needle leaf evergreen forest blankets the landscape. Evergreen forest covers 30% of the course of the Uele River, and 44% percent of the Bili River (Orange 1998).  

Fish Fauna:

The headwaters of the Congo basin are poorly known biologically and hydrologically, including the Uele River and its affluents. Current information suggests that the rivers of the Uele basin are rich in fish and aquatic herpetofauna. At least 136 fish species have been documented. Predominant fish families are Mormyridae (with an exceptional over 30 species), Cyprinidae (over 20 species), Alestidae (over a dozen species), Citharinidae (at least 10 species), Distichodontidae (at least seven species), Mochokidae (over a dozen species), Schilbeidae (seven species) and Cichlidae. Less species-rich but common families in the Uele ecoregion are Clariidae, Amphiliidae, Polypteridae, Mastacembelidae, Tetraodontidae, Malapteruridae, Anabantidae, Centropomidae, Hepsetidae, Channidae, and Bagridae.

Description of endemic fishes:

Based on collected data, the ecoregion exhibits a low level of endemism in fish, although this may be due to low sampling effort. Nine fish species are considered endemic although seven of them are only reported from their type locality in the Uele system: Amphilius notatus, Distichodus langi, Clariallabes simeonsi, Chrysichthys uniformis, Barbus schoutedeni, Barbus urotaenia, Hippopotamyrus macroterops, Hippopotamyrus retrodorsalis,and Petrocephalus hutereaui. Further investigations in the Upper Congo River basin may reveal occurrences of these species outside the Uele system.

Other noteworthy aquatic biotic elements:

Many frogs, reptiles, and mammals also depend on the freshwater systems of this ecoregion. About seventy frogs are known, of which about a dozen are considered endemic. The Central African giant terrapin (Pelusios chapini), West African flapshell turtle (Cycloderma aubryi), and slender-snouted crocodile (Crocodylus cataphractus) are among the aquatic reptiles native to the ecoregion. Aquatic mammals include the giant otter shrew (Potamogale velox), marsh mongoose (Atilax paludinosus), swamp otter (Aonyx congicus), spot-necked otter (Lutra maculicollis), aquatic genet (Osbornictis piscivora), hippopotamus (Hippopotamus amphibius), and African water rat (Colomys goslingi).

Level of taxonomic exploration:

Poor

References/sources:

Orange, D. (1998). "Matter transports in humid tropical watershed in a forested area: the Uele river in Zaïre"

Sayer, J. A., Harcourt, C. S., et al. (1992) The conservation atlas of tropical forests: Africa. London, UK: IUCN.

Wcmc (1984) "World Heritage Sites: Garamba" <http://www.wcmc.org.uk/protected_areas/data/wh/garamba.html>(2001)

The Nature Conservancy World Wildlife Fund
©WWF/TNC 2008 | Copyright Notice | Sponsors |Last updated: May 15, 2014