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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

563: Eastern Zimbabwe Highlands

Major Habitat Type:

montane freshwaters

Author:

Belinda Day, Freshwater Research Institute, Zoology Department, University of Cape Town, Cape Town, South Africa

Reviewers:

Paul Skelton, South African Institute for Aquatic Biodiversity (formerly J.L.B. Smith Institute of Ichthyology), South Africa

Countries:

Mozambique; Zimbabwe

Boundaries:

The Eastern Zimbabwe Highlands ecoregion is defined by the high-elevation easternmost rim of the central-southern African plateau and encompasses the Nyanga and Chimanimani mountain ranges. The ecoregion forms a narrow, north-south oriented belt, 450km long, along the eastern border of Zimbabwe with Mozambique.

Main rivers or other water bodies:

A number of rivers drain the Eastern Zimbabwe Highlands. The Nyanga Mountains form the watershed divide on which tributaries of the Pungwe, Save and lower Zambezi Rivers arise. These tributaries include the Pungwe, Kairezi, Nyangombe, Nyazengu, and Ruenya Rivers. The headwaters of the Odzani, Revue, and Nyamahwarara Rivers drain the Nyanga Lowlands and Honde Valley. Tributaries of the Lower Save and Buzi (whose main tributaries are the Revue, Rusitu, and Haroni Rivers) drain the Chimanimani mountains before flowing eastwards through Mozambique. The Pungwe and Save basins, which cover the northeastern and southwestern highlands, respectively, are two of the major river systems in Zimbabwe (Sanyanga 1994). 

Topography:

The topography of this ecoregion is diverse, with rolling hills lying below massive mountain peaks separated by dramatic river gorges, waterfalls, and steep-sided valleys. The land rises to the east, where the rim of the escarpment forms a high altitude north-south oriented ridge, broken in places by fertile lower-lying river valleys, including the Honde, Rusitu and Burma valleys. In the south, altitudes are generally between 1,500 and 1,900 m. The highest peaks of the Chimanimani Mountains and Umkondo Highlands reach above 2,000 m (Childes & Mundy 1998). Further north, in the region to the southeast of Mutare, the highlands form a dissected plateau approximately 1,700m above sea level. The highest region of the Eastern Highlands is the Nyanga Mountains in the north, with Mount Inyangi the highest point in Zimbabwe (2,592 m).

Climate:

Although the ecoregion falls within the tropics, the climate is essentially temperate due to its high altitude. Above 1,800 m temperatures are relatively low, with summer maxima of 25oC and mean annual temperatures between 15 and 17.5oC (Childes & Mundy 1998; Mtetwe 2000). At lower altitudes the climate is more subtropical, with temperatures often exceeding 35oC in summer (Childes & Mundy 1998). There is a warm dry season from August to October, a warm wet season from November to March, and a cool dry season between April and July. Precipitation is orographic: south-easterly monsoon winds, blowing across Mozambique from the Indian Ocean, are forced up onto the plateau and release their moisture as rain. Rainfall is high and highly predictable, with a prolonged rainy season from October to April (Mtetwe 2000). Most of the highlands receive a mean annual rainfall of over 1,500 mm and many of the highest peaks receive in excess of 3,000 mm (Hughes & Hughes 1992; Childes & Mundy 1998). Frost is common during winter (May to August) and mists or light rains are frequent during the dry season.

Freshwater habitats:

The Eastern Zimbabwe Highlands are deeply dissected by the headwaters of numerous rivers. Many streams flow eastwards for a short distance before descending high waterfalls at the rim of the escarpment into Mozambique. The topography is spectacular, with deep ravines and gorges separated by steep valleys. The streams are high altitude, narrow mountain torrents, with rapid flow and rocky substrata. Most streams are oligotrophic, apart from the Gairezi River, which is naturally eutrophic (Bell-Cross & Minshull 1988). As the river valleys are narrow and steep, floodplains and swamps are very rare, even at lower altitudes (Hughes & Hughes 1992). Springs and small lakes are, however, numerous at high altitudes. Dambos, which are seasonally waterlogged grasslands found in the valley bottoms, are found on granites and granitic gneisses along the headwaters of many of the streams (Chabwela 1994).

Terrestrial Habitats:

Rainfall decreases from east to west, such that eastern slopes tend to be well forested but western slopes tend to support grasslands and woodlands adapted to the drier conditions. Soils in the Eastern Highlands are coarse-grained, old and highly leached sandy loams. The dominant vegetation type above 1,800 m is Afromontane Themeda grassland, which contains a variety of herbaceous plants and includes some Afro-alpine species. Between 1,650 and 1,800 m, Syzygium montane forest dominates. The wetter eastern mountain slopes and protected ravines and gullies are covered with Afromontane rainforest. Further west the grasslands are drier and flatter and are interspersed with scattered areas of dwarf Brachystegia spiciformis woodland. Below 1,650 m the climate is more subtropical and medium-altitude rainforests dominate. Low-altitude forests occur below this altitude, with Brachystegia woodlands predominating. The large commercial tea plantations in the Nyanga area are characterised by the presence of Maranthes goetzeniana, Newtonia buchananii,and Xylopia aethiopica, all lowland forest species. Streams in the Gurungwe Peak area to the south-east support Breonadia microcephala along their banks (Childes & Mundy 1998).

Soils in the Chimanimani Mountains in the south of the ecoregion are extremely nutrient-poor and sandy, with poor water retention properties. These unusual soils have resulted in the evolution of floral endemics, which have more in common with the southern African Drakensberg species than with other Zimbabwean species. The dominant vegetation types on the plateau in the Chimanimani Mountains are montane grasslands, interspersed with Erica, Protea and Phillipia scrub, with Afromontane forests in the wetter valleys. Dry montane forests are found below 1,500 m, and in drier areas Miombo woodlands replace these forests. River valleys in the Save catchment are characterized by evergreen riparian forests (Campbell 1994). The forests include species such as Acacia albida, Guibourtia conjugata, Cordyla africana, Salvadora angustifolia, Azima tetracantha, Terminalia gazensis, Croton megalobotrys, Pteleopsis myrtifolia, and Xanthocercis zambesiaca (Hughes & Hughes 1992).

Fish Fauna:

The rivers and streams of the Eastern Highlands have at least 32 fish species. Small barbs (Barbus spp.) are particularly common and Bell-Cross and Minshull (1988) mention a minimum of 12 species.

Description of endemic fishes:

Four endemic fish (Labeo baldasseronii, Amarginops hildae, Varicorhinus pungweensis and Parakneria mossambica) have been described.

Other noteworthy aquatic biotic elements:

Little work has been done on the freshwater fauna and flora of the ecoregion, but the area contains high rates of endemism in terrestrial flora and fauna. For example, the Chimanimani Mountains are the area of highest plant biodiversity in Zimbabwe, with approximately 60 endemic species, although most are not wetland species (Childes & Mundy 1998).

The Eastern Zimbabwe Highlands are also rich in amphibians. A number of rare and range-restricted amphibians occur in this ecoregion, three of which are endemic – Bufo inyangae, Probreviceps rhodesianus, and Afrana inyangae.

The region supports few rare or restricted range wetland bird species; though the endangered blue swallow (Hirundo atrocaerulea) requires water for nest building and will only construct nests within the vicinity of wetlands (Childes & Mundy 1998). Breeding pairs of the vulnerable wattled crane (Grus carunculatus) also occur. The river valleys and riparian woodlands of the ecoregion are important for a number of bird species and nine Important Bird Areas occur in the highlands, mainly in forest-grassland mosaic habitats (Childes & Mundy 1998; Parker 2001).

Justification for delineation:

Skelton (1993) considers this ecoregion to be part of the Montane-escarpment aquatic region in Southern Africa, based on fish distributions. The montane-escarpment aquatic region has generally high-gradient streams with cool temperatures and is fragmented into highland “islands” and includes this ecoregion, along with the Drakensburg-Maloti Highlands [574] and Amatolo-Winterberg Highlands [577]. The fish fauna is depauperate and includes several characteristic species like mountain catlets (Amphiliidae) and chiselmouths (Skelton 1993; Tweddle & Skelton 1998).

Level of taxonomic exploration:

Poor. There are few publications on the freshwater ecosystems of the Eastern Zimbabwe Highlands and many of the freshwater taxa, particularly the invertebrates, are all but unknown. For example, data on both the vegetation and invertebrates of Zimbabwean fresh waters are insufficient to allow the identification of freshwater bioregions (Mtetwe 2000). Studies of the aquatic invertebrate fauna of the highland streams would prove extremely useful in assessing the ecological distinctiveness of the Eastern Zimbabwe Highlands.

References/sources:

Bell-Cross, G.,Minshull, J. L. (1988). "The fishes of Zimbabawe" Harare, Zimbabwe: National Museums and Monuments of Zimbabwe.

Campbell, B. M. (1994)"The environmental status of the Save Catchment" In Matiza, T.;Crafter, S.A. (Ed.). Wetlands ecology and priorities for conservation in Zimbabwe. Gland, Switzerland: IUCN.

Chabwela, H. N. (1994)"Current threats to the wetlands of Zimbabwe" In Matiza, T.;Crafter, S.A. (Ed.). Wetlands ecology and priorities for conservation in Zimbabwe. Gland, Switzerland: IUCN.

Childes, S. L.,Mundy, P. J. (1998)"Important Bird Areas of Zimbabwe" In Barnes, K.N. (Ed.). The important bird areas of southern Africa. (pp. 355-384) Johannesburg, South Africa: BirdLife International.

Hughes, R. H.,Hughes, J. S. (1992). "A directory of African wetlands" Gland, Switzerland, Nairobi, Kenya, and Cambridge, UK: IUCN, UNEP, and WCMC.

Mtetwe, S. (2000) "Establishment of biomonitoring reference sites for Zimbabwe. A tool for effective integrated catchment management. Proceeding of the 1st WARFSA/WaterNet Symposium: Sustainable Use of Water Resources; Maputo, 1-2 November 2000". Zimbabwe.

Parker, V. (2001)"Mozambique" In Fishpool, L.D.C.;Evans, M.I. (Ed.). Important bird areas in Africa and associated islands: Priority sites for conservation. (pp. 627-638) Newbury and Cambridge, UK: Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11).

Sanyanga, R. A. (1994)"Tourism and wetlands management in Zimbabwe, with special reference to the Zambezi River System" In Matiza, T.;Crafter, S.A. (Ed.). Wetlands ecology and priorities for conservation in Zimbabwe. Proceedings of a seminar on the wetlands of Zimbabwe.. Gland, Switzerland: IUCN.

Skelton, P. H. (1993) A complete guide to the freshwater fishes of Southern Africa. South Africa: Southern Book Publishers, Halfway House.

Tweddle, D.,Skelton, P. H. (1998). "Two new species of Varicorhinus (Teleostei: Cyprinidae) from the Ruo River, Malawi, Africa, with a review of other southern African Varicorhinus species" Ichthyolological Exploration of Freshwaters 8 369-384.

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