Highveld grasslands cover a large portion of west-central South Africa. Grasslands all over the world have experienced dramatic habitat destruction as a result of anthropogenic changes. The Highveld Grassland is no exception, with agriculture severely fragmenting this once-expansive region. This ecoregion now provides the last remaining stronghold of a number of grassland species that have suffered major reductions in abundance in the grassland biome, and which are consequently threatened with extinction (e.g. the Blue Crane (Anthropoides paradisea). There is a relatively biodiverse vertebrate fauna, with 608 taxa recorded.
Location and general description
The ecoregion draws its name from the high interior plateau known as the Highveld, and the expansive cover of species-rich communities of grasses. The ecoregion is bordered by the Drakensberg in the east, the arid Karoo and Kalahari in the west, and the low-lying bushveld to the north. The Highveld Plateau is fairly level with elevations varying from 1400 metres (m) to 1800 m. The flat topography means that the landscape is traversed by many meandering rivers, with the grassland community historically playing an important role in natural water purification of the westward flowing rivers that originate on the Drakensberg escarpment. The functioning of this ecosystem has been disrupted in many areas by water transfer projects that have been built to supply greater Johannesburg with water.
The dominant vegetation comprises grasses, with geophytes and herbs also being well represented. Dominant and diagnostic grass species are Thatching Grass (Hyparrhenia hirta) and Catstail Dropseed Grass (Sporobolus pyramidalis). Non-grassy forbs include False Paperbark Thorn (Acacia sieberiana), Rhus rehmanniana, Selago densiflora, Spermacoce natalensis, Aandblom (Kohautia cynanchica), and Phyllanthus glaucophyllus.
Relatively high precipitation levels sustain the grasslands during the austral summer, with the mean annual range between 400 to 900 millimeters (mm). Frequent fires, frost, and heavy grazing - formerly by wild animals and now by cattle and sheep – suppress the presence of shrubs and trees. Mean maximum temperatures range from 21 to 24o Celsius (C), and mean minimums range from 3 to 6o C, with temperatures sometimes reaching 38o C in the summer and –11oC in the winter. Austral summer rainfall is not evenly distributed throughout the region, resulting in several different habitat types. Differences in habitat types are further accentuated by the variable soil characteristics of the region. Over most of the area sandstones and shales of the Karoo sequence are dominant. Deep red sandy loam soils dominate towards the cooler and wetter northeast portion of the ecoregion, and transition to shallower lithosols in the extreme northeast part of the ecoregion.
Some dissention surrounds the number of diagnostic habitat types that comprise Highveld Grasslands. Several authors prefer detailed subdivision, and others advocate the aggregation of habitat types. Here, the Highveld Grassland ecoregion is divided into three habitat types: (1) Kalahari/Karoo-highveld transition zone; (2) sweet grasslands; and (3) sour grasslands. In the western half of the ecoregion, a gradual transition occurs from the Karoo/Kalahari-highveld transition zone to the grassland habitats of the Highveld. Shrubs and trees grow in the transition zone, although grasses still dominate this zone. This ecotone borders the sweet grasslands, which occur predominately in areas with lower rainfall. They have low fiber content and retain nutrients in their leaves during the winter. In contrast, sour grassveld species are low and dense, have a high fiber content, and retain nutrients in the roots during the winter, making them largely unpalatable.
Although highly fragmented, the Highveld contains the greatest expanse of remaining grassland in southern Africa. Analyses of pollen spores from the Winterberg escarpment suggest that grasses have dominated the floral community since at least the early Holocene. At times, Highveld grassland types have expanded or contracted in response to climate change. During the Quaternary, grassland expanded in response to glacial events to the north. Global climate variation may again alter the ecotonal nature of the Karoo/Kalahari-highveld grassland in the extreme west of the ecoregion, with arid-adapted species of the Karoo/Kalahari ecoregions encroaching onto sweet grassland. Despite the severely degraded nature of the once pristine Highveld grassland, this ecoregion provides the last remaining stronghold of several grassland species that have suffered major reductions in abundance in the grassland biome (e.g. the Blue Crane (Anthropoides paradisea).
Bird species richness is relatively high within this ecoregion. However, Botha’s Lark (Spizocorys fringillaris) is the only bird species strictly endemic to the ecoregion, where it inhabits heavily grazed grassland. An additional six avian species are near-endemics including White-winged Flufftail (Sarothrura ayresii), Blue Korhaan (Eupodotis caerulescens), White-bellied Bustard (Eupodotis senegalensis), Rudd’s lark (Heteromirafra ruddi), melodious lark (Mirafra cheniana), buff-streaked chat (Oenanthe bifasciatai), and yellow-breasted pipit (Hemimacronyx chloris).
This ecoregion contains a higher number of mammals, although only the Orange Mouse (Mus orangiae) is restricted to the ecoregion, and the Rough-haired Golden Mole (Chrysospalax villosa) is near-endemic. The ecoregion also supports populations of several large mammal species, some of which are rare in southern Africa (Stuart and Stuart 1995). Among these are the Brown Hyena (Hyaena brunnea), African Civet Cat (Civettictis civetta), Leopard (Panthera pardus), Sable Antelope (Hippotragus niger), Ground Pangolin (Manis temminckii), Honey Badger (Mellivora capensis), African Striped Weasel (Poecilogale albinucha), Aardwolf (Proteles cristatus), Oribi (Ourebia ourebi), and Hartmann's Mountain Zebra (Equus zebra hartmannae). Herds of large mammals, including Black Wildebeest (Connochaetes gnou) and White Rhinoceros (Ceratotherium simum), previously occurred in the Highveld grasslands, but were extirpated by the local human population.
Relatively few reptile species occur within the ecoregion, mainly due to its cool climate. However, the ecoregion supports some of Africa’s most characteristic reptile species, including Nile Crocodile (Crocodylus niloticus), African Rock-python (Python sebae), Nile Monitor (Varanus niloticus) and Veld Monitor (Varanus albigularis albigularis). There are also two strictly endemic reptiles: Giant Girdled Lizard (Cordylus giganteus) and Agama aculeata distanti (Branch 1998). Several additional reptile species are near-endemics, including Drakensberg Rock gecko (Afroedura niravia), Giant Girdled Lizard (Cordylus giganteus), and Breyer's Whip Lizard (Tetradactylus breyeri) (Branch 1998).
Twenty-nine amphibians occur within the ecoregion but none are endemic (Passmore and Carruthers 1995). Example anuran species in the Highveld grasslands are the African Dwarf Toad (Poyntonophrynus vertebralis), who breeds in temporary shallow pans, freshwater pools or depressions containing rainwater; the Red Toad (Schismaderma carens); Cape River Frog (Amietia fuscigula). endemic of the high slopes of the Drakensberg Mountains and Lesotho Highlands; South African Snake-necked Frog (Phrynomantis bifasciatus), typically found under loose sand below large rocks or boulders.
The grassland habitat that has remained in a near-pristine state is found mostly in nature reserves. The main protected areas are Valei, Nooitgedacht Dam, Bronkhortspruitdam, Vaal Dam, Willem Pretorius, Rustfontein Dam and Koppies Dam Nature Reserves, and the Ermelo Game Park. Together with a number of smaller reserves, these currently conserve only 0.5 percent of the ecoregion. Even the areas of grassland habitat that have remained in a near-natural state are declining steadily in area and quality. The present state of fragmentation, together with anthropogenic changes planned for the coming years may lead to the extinction or near-extinction of some larger animal species, such as the blue crane (Anthropoides paradisea).
The Highveld grasslands have suffered extensive degradation. Because it is highly suited for agriculture relative to other areas in South Africa, large tracts of land have already been converted to agriculture, chiefly for corn production. Urban expansion, fire, and overgrazing have led to increased habitat fragmentation, as has coal mining and afforestation for stands of exotic trees, especially by species of Eucalyptus. Over several hundred years, particularly around towns, planted wattle (Acacia mearnsii) has become invasive, and is prone to rapid expansion up river watersheds. In the future, expanded surface activity associated with mining below the grassland may become a greater concern as companies develop new technology to make deep mining of coal more profitable.
The Highveld plays an important role in natural water purification, as the peat formed here has been shown to filter out 90 percent of the harmful chemicals in herbicides. Peat is also useful in absorbing various other pollutants, as a source of fuel, in horticulture, and for medicinal purposes. In South Africa, where clean water resources are already particularly valuable, this natural filter is being extracted from the Highveld at an unprecedented rate. Approximately 60 percent of locally extracted peat is used to grow mushrooms, while the remaining 40 percent comprises "environmentally friendly" potting soil and compost. Peat has an extremely slow regeneration rate, increasing between 0.7 mm to 1.2 mm per year depending on environmental conditions (Dada 1999). Given its slow formation process, it is unlikely this resource will recover in millennia from the damage caused by its rapid removal. Hence, the Highveld’s role as a natural filtration process for scarce water resources could be in jeopardy. The preservation of this resource is imperative, and could be fulfilled by moderating or halting the use of peat for gardening purposes.
Justification of ecoregion delineation
This ecoregion, distinguished from surrounding ecoregions by its higher elevations on the Highveld Plateau, follows Low and Rebelo’s highveld grasslands. These include ‘rocky highveld grassland,’ moist clay highveld grassland,’ ‘dry clay highveld grassland,’ ‘moist sandy highveld grassland,’ ‘ moist cool highveld grassland,’ and ‘moist cold highveld grassland.’ The lumping of these finer units corresponds closely to the ‘Highveld grassland’ vegetation unit of White.
References and further reading
- Acocks, J.P.H. 1988. Veld types of South Africa. Memoirs of the Botanical Survey of South Africa 57: 1-146. (An update of the first edition published in 1953),
- Allan, D.G. 1992. Distribution, relative abundance and habitat of the Blue Crane in the Karoo and the southwestern Cape. Proceedings of the first southern African crane conference. Pages 29-46 in D.J. Porter, editor. South African Crane Foundation, Durban.
- BirdLife International. 2000. Threatened Birds of the World. Lynx Edicions and BirdLife International, Barcelona and Cambridge, UK.
- Branch, W. 1998. Field guide to snakes and other reptiles of southern Africa. Struik, Cape Town. ISBN: 0883590425
- Bredenkamp, G.J., A.F. Joubert, and H. Bezuidenhout. 1989. A reconnaissance survey of the vegetation of the Potchefstroom-Fochville-Parys area. South African Journal of Botany 55: 199-206.
- Coetzee, J.P., G.J. Bredenkamp and N. Van Rooyen. 1993. The sub-humid warm temperate mountain bushveld plant communities of the Pretoria-Witbank-Heidelberg area. South African Journal of Botany 59: 623-632.
- Cowling, R.M., D.M. Richardson, and S.M. Pierce. 1997. Vegetation of South Africa. Cambridge: Cambridge University Press.
- Dada, R. 1999. How compost is killing the wetland. Africa News Service. March 5.
- Davies, B. and J. Day.1998. Vanishing Waters. University of Cape Town Press, Cape Town.
- Eckhardt, H.C., N.Van Rooyen, and G.J. Bredenkamp. 1993. An overview of the vegetation of the Vrede-Memel_warden area, north-eastern Orange Free State. South African Journal of Botany 59: 391-400.
- Fuls, E.R.,G.J. Bredenkamp, N. Van Rooyen, and G.K. Theron. 1993. The physical environment and major plant communities of the Heilbron-Lindley-Warden-Villiers area, northern Orange Free State. South African Journal of Botany 59: 345-359.
- Harrison, J.A., D.G. Allan, L.G. Underhill, M. Herremans, A.J. Tree, V. Parker, and C.J. Brown, editors. 1997. The atlas of southern African Birds Vols 1and 2. BirdLife South Africa, Johannesburg.
- Hilton-Taylor, C. 2000. 2000 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, United Kingdom. ISBN: 2831705657
- Low, A.B. and A.G. Rebelo, 1998. Vegetation of South Africa, Lesotho and Swaziland. Department of Environmental Affairs and Tourism, Pretoria. 2nd ed.
- Mallett, V. 1999. After Hours- Journey to the center of the earth. Business Day. July 16.
- Meadows, M.E. and H.P. Linder, 1993. A palaeoecological perspective on the origin of afromontane grasslands. Journal of Biogeography 20: 345-355.
- Meadows, M.E. and K.F. Meadows. 1988. Late Quaternary vegetation history of the Winterberg mountains, eastern Cape, South Africa. South African Journal of Science 84: 253-259.
- Passmore, N. and V. Carruthers, 1995. South African Frogs: a complete guide. Witwatersrand University Press, Johannesburg. ISBN: 1868125173
- Rutherford, M.C. and R.H. Westfall. 1986. Biomes of southern Africa – an objective categorization. Memoirs of the Botanical Survey of South Africa 54: 1-98.
- Siegfried, W.R. 1992. Conservation status of the South African endemic avifauna. South African Journal of Wildlife Research 22: 61-64.
- Stuart, C. and T. Stuart.1995. Field Guide to the Mammals of Southern Africa. Struik, Cape Town. ISBN: 0883590476
- White F. 1983. The Vegetation of Africa, a descriptive memoir to accompany the UNIESCO/AETF AT/UNSO Vegetation Map of Africa (3 Plates, Northwestern Africa, Northeastern Africa, and Southern Africa.,1:5,000,000). Paris: UNESCO.
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