Coastal East Africa



ID

564

Author(s)

Dalmas Oyugi, National Museum of Kenya, Nairobi, Kenya; Michele Thieme and Ashley Brown, Conservation Science Program, WWF-US, Washington, DC, USA


Countries

Malawi
Mozambique
Tanzania

Reviewer(s)

Lucy Kashaija, World Wildlife Fund – Tanzania Programme Office, Dar es Salaam, Tanzania


Major Habitat Type

Tropical and subtropical coastal rivers

Drainages flowing into

Indian Ocean


Main rivers to other water bodies

From north to south, the major river drainages are the Wami, Ruvu, Rufiji (whose tributaries include the Great Ruaha, Kilombero, Luwego, and Mbarangandeu), Matandu, and Mbemkuru. The Wami River drains the Nguu, Nguru, Ukaguru and Rubeho Mountains of the ‘Eastern Arc’ mountain range. The shorter Ruvu River flows from the Uluguru Mountains onto the coastal plain. The Rufiji River, the largest in Tanzania, has several major tributaries, including the Ruhudji, with floodplains along the Kilombero Valley (up to 6,265 km2), the Great Ruaha, Njombe and Luwegu rivers. These rivers have their major headwaters in the Udzungwa and Mahenge Mountains of the Eastern Arc and the more southern Kipengere Range (Southern Highlands). The Rufiji is lined by a number of small temporary and permanent lakes that includes the Tangalala Lake Complex, a series of connected lakes (Manongi 1993). Larger rivers of northern Mozambique include the Ruvuma, Messalo, Lúrio, Mocubúri, Ligonha, and the Licungo, all of which drain the highland interior (900-2,500 m asl) to the coastal plain. The Ruvuma River is the third largest in Mozambique and has a catchment area of 155,400 km2 (Hughes & Hughes 1992). Swamps that line the lower reaches of the Ruvuma include the Nhica (75 km2), the Quitemba (25 km2), and the Miula (70 km2). Lake Nangade and several other oxbow lakes also occur in the river’s floodplain. Lakes Chilwa and Chiuta are shallow lakes at the headwaters of the Lugenda River, a tributary of the Ruvuma River. South of the Ruvuma, the Messalo, Montepuez, Megaruma, Lúrio, Mocubúri, and Monapo Rivers all have seasonal flows and most are lined by swamps. The lower courses of several of these rivers expand out into narrow, long lakes, such as Lake Biribizi on the Montpuez River (Hughes & Hughes 1992).



Description

Boundaries

This ecoregion, situated along the eastern coasts of Tanzania and Mozambique, extends from the Wami River basin southwards to the Luala River basin, directly above the Lower Zambezi basin [561]. The ecoregion includes Lakes Chilwa and Chiuta, the Ruaha/Rufiji, Ruvuma, and Lúrio Rivers, as well as other smaller coastal basins.

Topography

In the Tanzanian portion of the ecoregion, rivers descend from the escarpments and highlands of the interior to the narrow coastal plain (15 km to 30 km wide).

Freshwater habitats

The habitats in the ecoregion include forested headwater streams, medium-sized rivers and their tributaries, mangrove forests, estuaries, small lakes, permanent swamps, dambos, deltas, and seasonal floodplains. Lake Chilwa is a unique, closed system with extensive Typha swamps, saline waters, and highly variable lake extent and water quality.

Terrestrial habitats

Vegetation adjacent to and within the freshwater systems of this ecoregion consists primarily of a coastal mosaic including large areas of miombo woodland, coastal dry forest and coastal scrub, riparian and swamp forests, floodplain vegetation, and mangrove forests (Hughes & Hughes 1992; Hatton & Munguambe 1998; Burgess & Clarke 2000). Swamp and riparian forest trees include Pandanus rabaiensis, Baikiaea insignis, Syzygium cordatum, Ficus verruculosa, F. trichopoda, Voacanga thouarsii, Raphia farinifera,and Parkia filicoidea. Cyperus papyrus also grows in permanent swamps lining the rivers, often in association with Phragmites spp. and Nymphaea capensis (Hughes & Hughes 1992). Grasses such as Echinochloa pyramidalis, Cynodon dactylon, and Oryza spp. dominate many of the floodplains of the ecoregion, whereas hygrophilous (living or growing in moist places) grass species such as Andropogon schirensis, Digitaria milanjiana, Loudetia phragmitoides, and others dominate dambos (seasonally waterlogged, predominantly grass-covered, shallow depressions in the headwater zone of rivers that are generally less than 5 km2) within the ecoregion (Hatton & Munguambe 1998). Mangrove forests line river mouths throughout the ecoregion (Hughes & Hughes 1992; Kemp et al. 2000). The montane headwaters of the rivers in this ecoregion are clothed with montane cloud forests, which are rich in endemic species of plants and animals (Lovett & Wasser 1993; Burgess et al. 1998).

Description of endemic fishes

About thirty percent of the -nearly 100 described fish species are endemic. Among endemic fish, there is a radiation of the Aplocheilidae genus Nothobranchius, with nine endemics known from this ecoregion (Lévêque 1997). The Cichlid Haplochromis tweddlei is, as yet, known only from Lakes Chilwa and Chiuta and may be endemic to the larger Ruvuma system (Roberts 1975; Tweddle 1983).

Other noteworthy fishes

The presence of the tank goby, Glossogobius giuris, in Lake Chiuta suggests there is (or historically was) no barrier to upstream movement of fishes in the Ruvuma/Lugenda River system. The absence in the Chilwa catchment of Chiuta species Mormyrus longirostris, M. cf. brevianalis, Labeo sp., B. orientalis and Synodontis sp. is probably related to a lack of a suitable habitat and historical access. The absence of G. giuris is less easy to explain as it can survive in saline conditions.

Ecological phenomena

BirdLife has identified Lake Chilwa as an important area for congregations of waterbirds. Significant populations of Egretta ardesiaca, Plegadis falcinellus, Platalea alba, Dendrocygna bicolor, Amaurornis flavirostra, Gallinula angulata, Porphyrio alleni, P. porphyrio, and Rynchops flavirostris have been documented on the floodplains of the lake (Dowsett-Lemaire et al. 2001).

Justification for delineation

This ecoregion includes coastal basins from the Wami River in Tanzania to the Luala River in Mozambique and includes the Ruaha/Rufiji, Ruvuma, and Lúrio Rivers, as well as other smaller basins. The relatively depauperate freshwater fish fauna of the rivers of this coastal ecoregion has its greatest affinities with the Zambezi fauna (Bills 1997; Lévêque 1997). Many of these rivers may have been dry as recently as the last interpluvial, which accounts for their low species counts (Roberts 1975). The Tanzanian Shield rivers, meaning those rivers between the Athi basin in the Kenyan Coastal Rivers ecoregion [864] to the Zambezi in the Lower Zambezi ecoregion [866], at times converged due to fluctuations in sea level and may account for the similarity in fauna among many of the coastal rivers of the Eastern Coastal ecoregion (Lévêque 1997).

Level of taxonomic exploration

Poor


References

  • Baker, N. E.;Baker, E. M. (2001). "Tanzania" Fishpool, L. D. C.;Evans, M. I. ( (Vol. Important bird areas in Africa and associated islands: Priority sites for conservation, pp. Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11) ) 897-945.
  • Baker, N. E.;Baker, E. M. (2002) \Important Bird Areas in Tanzania: A first inventory\ (Dar es Salaam, Tanzania)
  • Bills, R. (1997) \Freshwater of the Moebase region and their fish communities. Environmental impact assessment of the proposed TIGEN sands mineral mine, Zambezia Province, Mozambique\ Grahamstown, South Africa. Coastal Environmental Services.
  • Burgess, N. D. and Clarke, G. P. (2000). Coastal forests of eastern Africa, IUCN Forest Conservation Programme Gland, Switzerland: IUCN.
  • Burgess, G. H. and Franz, R. (1989). "Zoogeography of the Antillean Freshwater Fish Fauna" C. A. Woods and F. E. Sergile (Ed.) Biogeograpy of the West Indies: Patterns and Perspectives ( pp. 263-304 ) Boca Raton, FL, USA: CRC Press.
  • Clausnitzer, V. (2001). "Notes on the species diversity of East African Odonata, with a checklist of species" Odonatologica 30 (1) pp. 49-66.
  • Dowsett-Lemaire, F., Dowsett, R. J. and Dyer, M. (2001). "Malawi" L. D. C. Fishpool and M. I. Evans (Ed.) Important bird areas in Africa and associated islands: Priority sites for conservation ( pp. 539-555 ) Newbury and Cambridge, UK: Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11).
  • Dudley, C. O., Stead, D. E. and Schulten, G. G. M. (1979). "Amphibians, reptiles, mammals and birds of Chilwa" M. Kalk, A. J. McLachlan and C. Howard-Williams (Ed.) Lake Chilwa: Studies of change in a tropical ecosystem, Monographiae Biologicae 35 ( pp. 247-273 ) The Netherlands: Dr. W. Junk.
  • Hatton, J. and Munguambe, F. (1998) \The biological diversity of Mozambique\ Maputo, Mozambique. Ministry for the Coordination of Environmental Affairs.
  • Hughes, R. H.;Hughes, J. S. (1992). "A directory of African wetlands" Gland, Switzerland, Nairobi, Kenya, and Cambridge, UK: IUCN, UNEP, and WCMC.
  • Kemp, J.,Hatton, J. C.;Sosovele, H. (2000). "East African marine ecoregion: Reconnaissance synthesis report" Tanzania: WWF.
  • Lévêque, C. (1997). Biodiversity dynamics and conservation: The freshwater fish of tropical Africa Cambridge, UK: Cambridge University Press.
  • Lovett, J. C., Hatton, J., Mwasumbi, L. B., et al. (1997). "Assessment of the impact of the lower Kihansi hydropower project on the forests of Kihansi Gorge, Tanzania" Biodiversity and Conservation 6 (7) pp. 915-933.
  • Manongi, F. J. (1993). "River basin planning and management of wetlands" G. L. Kamukala and S. A. Crafter (Ed.) Wetlands of Tanzania: Proceedings of a seminar on wetlands of Tanzania, Morogoro, Tanzania Gland, Switzerland: IUCN.
  • Roberts, T. R. (1975). "Geographical distribution of African freshwater fishes" Zool. J. Linn. Soc. 57 pp. 249-319.
  • Schiøtz, A. (1999). Tree frogs of Africa Frankfurt, Germany: Edition Chimaira.
  • Stattersfield, A. J.,Crosby, M. J.,Long, A. J.;Wege, D. C. (1998). "Endemic bird areas of the world: Priorities for biodiversity conservation" Cambridge, UK: BirdLife International.
  • Tweddle, D. (1983). "The fish and fisheries of Lake Chiuta" Luso: J. Sci. Tech. (Malawi) 4 (2) pp. 55-81.