Boundaries

The Drakensberg-Maloti Highlands are highly valued in southern Africa for their rivers’ excellent water quality and high water yield. These rivers provide water to large areas of xeric South Africa. The ecoregion encompasses the whole of Lesotho, excluding the westernmost lowland areas. It also includes small parts of South Africa just south and north of Lesotho.

Topography

The whole of the ecoregion lies above 1,850 m asl and slopes upwards towards the east, where the border with the KwaZulu-Natal province of South Africa forms the rim of the southern African plateau. The steep formations along the uplifted edges of the plateau make up the Great Escarpment, of which the Drakensberg comprises the eastern portion. Within this ecoregion, the highest part of the Drakensberg Escarpment forms a ridge at a height of over 3,000 m, with spectacular drops of between 500 and 700 m (Hughes & Hughes 1992).

The terrain of the highlands ranges from undulating hills to rugged peaks and headlands intersected by deep valleys and ravines. The highest peak in southern Africa, Thabana-Ntlenyana (3,482 m), is located in this ecoregion, and the whole of the eastern half of Lesotho lies above 2,440 m (Hughes & Hughes 1992; Barnes 1998). The mountains and peaks of the Lesotho Highlands above 2,300 m consist of basalts, extruded approximately 180 million years ago during a massive series of tectonic events. Underlying the basalts are horizontal sedimentary strata topped by soft sandstones (Barnes 1998).

Freshwater habitats

The streams of this ecoregion tend to be steep (dropping up to 1,200 m in 60 – 70 km) and fast-flowing. Upon reaching the foothills and lowlands in the west, the rivers slow down and widen, often forming small floodplains and marshes (Hughes & Hughes 1992).

Pans (areas without external drainage, some of which seasonally dry out), marshes (often with reedbeds), tarns (shallow pools and pans that typically form on sandstones), and bogs and sponges (some of which have been re-classified as midslope and valleyhead fens) are common in the highlands (Lesotho Government 2000). They are especially prevalent in the northeast, where rainfall is highest, and decrease in both size and frequency to the south and west. Most occur in the soft sandstone of the alpine regions above 2,300 m. Bogs and sponges collectively cover thousands of hectares but most are individually small (Hughes & Hughes 1992; Barnes 1998). They are found at all altitudes, wherever there is a continuous or semi-continuous source of water. This distribution extends to extremely high altitudes, such as on the plateau along the rim of the Drakensberg Escarpment and on summits of peaks such as Thabana Ntlenyana. Pans are found in a few places in the highveld grasslands both at lower altitudes and on several of the plateaus, whereas marshes are less common due to harvest of reeds. Marshes remain at Tebeteben, Mohlaka-oa-tuka, and Koro-Koro (Lesotho Government 2000). Tarns occur in depressions in soft sandstones, such as those found in the Sehlabathebe National Park (Hughes & Hughes 1992).

The Drakensberg-Maloti Highlands contain rare examples of Afromontane and Afro-alpine rivers and other wetlands (Lesotho Government 2000). The high altitude wetlands found in this ecoregion have limited occurrences in the Eastern Cape and are found nowhere else in southern Africa (Wetlands International 2002).

Terrestrial habitats

The Drakensberg-Maloti Highlands ecoregion falls within the Afromontane and Afro-alpine bioregions (Stuart et al. 1990). The Lesotho Government (2000) classifies the vegetation into three types: Highveld grassland (1,400 – 1,800 m), Afromontane grassland (1,800-2,500 m), and Afroalpine grassland (above 2,500 m). Each of the various types of wetlands in the ecoregion is characterized by a different vegetation community. For example, montane sandstone pools are characterized by aquatic species such as Limosella spp., Utricularia spp., Ilysanthes confertiflora, and Aponogeton ranunculiflorus, whereas gravel-filled pools tend to support Crassula galpinii. Crassula natans, Aponogeton spathaceum, and Limosella maior are found in sandstone pools in the foothills.

Description of endemic fishes

The only endemic, the Maloti minnow, Pseudobarbus quathlambae, is known only from six high-altitude tributaries of the Orange River. It is critically endangered due to habitat degradation and alteration, and competition with and predation by alien trout species (Stuart et al. 1990; Rall & Skelton 2001).

Justification for delineation

The delineation of this ecoregion follows the boundaries of the Drakensberg-Maloti Highlands and comprises the middle sub-region of the Montane-escarpment aquatic region (Skelton 1993). The Drakensberg-Maloti Highlands are a residual portion of the peripheral uplands of the Great Escarpment that has progressively been eroded and dissected northward and westward by the rivers on the southern and eastern southern African coasts (Truswell 1977; Corbett 1979 in Skelton 1986) (Trusw. Relict fauna and flora of Afromontane species are present in the highlands and a comprehensive treatment of the fish biogeography of the region is presented by Skelton (1994)(Skelton 1994).

Level of taxonomic exploration

Little is known about the historical distribution, habitat requirements, biology, or life history of most of the wetland taxa, particularly the invertebrates, in the Drakensberg-Maloti Highlands. It seems likely however, from the results of the few taxa that have been studied, that further investigation may reveal a diverse fauna that could include endemic or relict species. As many of the taxa in Lesotho are seriously threatened, it is essential that research, monitoring, and conservation are made a priority before ecosystems are permanently degraded and destroyed.