Southern Africa bushveld
The Southern Africa bushveld is an element of the vast savannas that cover much of southern Africa. There is low endemism in this ecoregion for both flora or fauna, but the charismatic large mammals and rich birdlife characteristic of African savannas are in evidence. The rugged Waterberg Mountains contain the highest levels of species richness and endemism in the region, and are noted for their reptilian endemism. Cattle ranching and urban expansion from the nearby Pretoria-Witwatersrand-Vereeniging complex are the major threats to the conservation of this ecoregion. However, ecotourism has become a major land-use commitment in the bushveld and has led to the establishment of a number of small nature reserves and private game parks, which augment the conservation status of this ecoregion.
The Southern African bushveld belongs to the savanna biome, the dominant vegetation assemblage of Africa, occupying 54 percent of southern Africa, 60 percent of sub-Saharan Africa, and twelve percent of the Earth's global land surface. Savannas are generally defined as a continuum of vegetation types with trees and grasses as their main constituents. The Southern African bushveld is a classic savanna, made up of a mix of vegetation types, with somewhat arbitrary delineations separating the different types. To the north, east, and west the ecoregion borders other savanna ecoregions and is mainly differentiated because of its high elevation (700 to 1100 metres).
The Southern African bushveld covers the southeast corner of Botswana, southern Zimbabwe and northern South Africa. It has a well-defined southern boundary, the Highveld grassland which is a cool, high-elevation (1500 to 2000 m) grassland that is exposed to frequent, severe frosts in winter. To the east, the ecoregion is bound by the mountain ranges of the Drakensberg, Strydpoortberg and Soutpansberg. The Zambezian and Mopane Woodland ecoregion is situated in the low-lying areas to the east of these mountain ranges. The western and northern boundaries are less well defined. To the west the climate becomes increasingly arid, and as a result, the soils are more fertile. The savannas characteristic of these arid, fertile environments are termed "arid fine-leaved savannas" and include the Kalahari Acacia-Baikiaea woodland and the Kalahari Xeric savanna ecoregions. To the north, the climate becomes moister, and as a result the soils are leached and rather infertile. The savanna characteristic of this moister environment are termed "moist broad-leafed savannas" or "semi-deciduous forests" and include the Zambezian Baikiaea woodland and the Southern Miombo woodland ecoregions. The low-lying Limpopo River Valley, cutting in from the east, is not included in this ecoregion, but rather with the Zambezian and Mopane woodland ecoregion.
The key feature common to savannas worldwide is climate, specifically, a hot wet season of four to eight months in duration, and a cool dry season for the remainder of the year. The Southern African Bushveld is typical in this regard, with hot, wet summers and cool, dry winters. It has an average annual rainfall of between 350 millimetres (mm) to 750 mm, with a slightly higher average (650 mm to 900 mm) in the Waterberg Mountains. The highveld plateau to the south forms a ridge running east to west, and provides shelter against cooler air masses from the south. As a result, the temperatures in the bushveld are higher than on the more elevated highveld and range from –3° C to 40° C, with an annual average of 21° C. Another distinguishing characteristic is the relative lack of frost in the bushveld. The ecoregion experiences mild frosts on a few occasions per year; whereas, the highveld is exposed to frequent severe frosts in winter.
The ecoregion occurs on an extensive, undulating interior plateau, which lies at an elevation between 700 metres (m) to 1100 m. The soils of this plateau are chiefly coarse, sandy and shallow, overlying granite, quartzite, sandstone or shale. The most distinctive topographical feature of the ecoregion is the rugged and rocky Waterberg Mountains, which rise up from the plateau to an elevation of between 1200 m to 1500 m. A flat plain known as the Springbok Flats extends into the southwest of the ecoregion. This plain is characterized by an unusual soil type: black or red vertic clay, derived from basalt.
The ecoregion is well-drained by the Limpopo River and the Olifants River. The Limpopo has the larger watershed area, covering most of the ecoregion. It receives tributaries from Botswana, Zimbabwe, and northern South Africa. The Olifants River has a smaller catchment and drains the eastern part of the ecoregion. These two rivers converge before discharging the combined flow into the Indian Ocean, immediately north of Maputo in Mozambique.
Cowling et al. divide the vegetation of this ecoregion into "mixed savanna" and "mopane savanna". Mopane savanna extends from southeastern Botswana into the main plateau of Zimbabwe and down into the north of South Africa, known as the Tuli Block. The mopane savanna is an exception to the "broad-leaved/fine-leaved" distinctions of Cowling et al. as it is a broad-leaved savanna that occurs on arid, fertile soils. The mopane savannas are dominated by often monospecific stands of the winter-deciduous mopane tree (Colophospermum mopane) (Caesalpinoideae family). This tree shows major plasticity in growth form, ranging from a dense shrubland to a tall, open woodland. This variability in growth form reflects growth conditions and a history of disturbance, especially by elephants. Towards the Tuli block in northern South Africa, C. mopane becomes less mono-dominant and is intermixed with other tree species such as umbrella thorn (Acacia tortilis) and blackthorn (A. mellifera). The "mixed savanna" described by Cowling et al. varies from a dense, low canopy bushveld to an open tree savanna.
To the north of the ecoregion (around Bulawayo in Zimbabwe) the vegetation turns into tree savanna about six metres in height with a plentiful grass cover. Hyparrhenia filipendula and yellow thatching grass (H. dissoluta) are the most common grass species. The silver clusterleaf (Terminalia sericea) is the dominant tree, intermixed with varying proportions of Burkea africana. To the north of this, Acacia species, such as Acacia nilotica, A. karoo and A. rehmanniana, become dominant. To the southwest of the ecoregion, on the Springbok Flats, a distinctive type of vegetation, the clay thorn bushveld, grows. This veld type is associated with the unusual basalt-derived clays of the flats. It is an open savanna dominated by many Acacia species, such as Acacia tortilis, A. nilotica, A. nigrescens, A. gerrardii, and A. karoo. The grasses are dense, tall, and coarsely tufted. Turf grass (Ischaemum afrum), deck grass (Sehima galpinii), and canary millet (Setaria incrassata) are the predominant Poaceae family species. The savanna surrounding the Waterberg Mountains is characterized by Willow beechwood (Faurea saligna), common hookthorn (Acacia caffra), Wild seringa (Burkea africana), Terminalia sericea, and African wattle (Peltophorum africanum). The rugged, rocky slopes of these mountains are dominated by woody species such as White seringa (Kirkia acuminata), Stem-fruit (Englerophytum magalismontanum), Red bushwillow (Combretum apiculatum), Velvet bushwillow (C. molle), and manica protea (Protea caffra).
A considerable number of mammalian species occur within the ecoregion including: Burchell's zebra (Equus quagga burchelli); Hippopotamus (Hippopotamus amphibius), a herbivore classified as Vulnerable; Cheetah (Acinonyx jubatus), a carnivore classified as Vulnerable; Commerson's roundleaf bat (Tomopterna cryptotis), classified as Near Threatened;
Amphibians of the ecoregion are represented by Garman's toad (Amietophrynus garmani), an anuran of broad distribution; Savanna ridged frog (Ptychadena anchietae); Angola frog (Rana angolensis); African gray treefrog (Chiromantis xerampelina); African clawed frog (Xenopus laevis); African split-skin toad (Schismaderma carens); African ornate frog (Hildebrandtia ornata); Knocking sand frog (Tomopterna krugerensis), which is found broadly in southern Africa; and the Transvaal short-headed frog (Breviceps adspersus); Horseshoe forest treefrog (Leptopelis bocagii); Boettger;s dainty frog (Cacosternum boettgeri); Cryptic sandfrog (Tomopterna cryptotis); Common reed frog (Hyperolius viridiflavus); Gray's stream frog (Strongylopus grayii); Garman's toad (Amietophrynus garmani); Flat-back toad (Amietophrynus maculatus).
A number of reptilian taxa occur within the Southern Africa bushveld: Bibron's worm snake (Typhlops bibronii); Vine snake (Thelotornis capensis); Black mamba (Dendroaspis polylepis); Angola garter snake (Elapsoidea semiannulata); Annobon lidless skink (Panaspis annobonensis); Bark snake (Hemirhagerrhis nototaenia); Bell's hingeback tortoise (Kinixys belliana); Blue throated agama (Acanthocercus atricollis); Blunt-tailed worm lizard (Dalophia pistillum); Bradfield's dwarf gecko (Lygodactylus bradfieldi).
In principle, the conservation status of the Southern African Bushveld is satisfactory. Many areas of natural habitat have been conserved in the form of provincial nature reserves, conservation areas and private game farms. Pilanesberg National Park, in the southwest of the ecoregion, is one of the most important reserves. This 553-square-kilometre (km2) national park encompasses an isolated ring complex of volcanic hills (one of three such ring complexes in the world). The park conserves a large area of "mixed savanna", dominated by Acacia karoo, A. caffra, and Faurea saligna. It is home to many threatened large mammals including black rhinoceros, African elephant, Cheetah and Brown hyena. In 1999, the park introduced nine African wild dogs (Lycaon pictus), which are critically endangered species. The Hans Strydom and Doorndraai Dam Nature Reserves are important in that they are situated in the Waterberg Mountain Range, which is home to a number of endemic plants and animals. Euphorbia waterbergensis, Hibiscus waterbergensis, and Aloe petrophila are examples of rare Waterberg endemics found in these reserves. The most threatened veld type in this ecoregion is found on the fertile clays of the Springbok Flats. Low and Rebelo estimate that 60 percent of this Springbok Flats veld type has been converted to agriculture. Only one percent of this veld type is conserved, within the Nylsvlei Nature Reserve.
In the Northern Province of South Africa there has been a recent trend to restock privately owned savanna areas with indigenous herbivores. These private game farms contribute significantly to conservation. It is estimated that there is more private land than state land under conservation management in the Northern Province. About nine percent of the Waterberg Mountains are conserved in these private conservation areas and game parks. While the percentage of habitat protected by the game farms is high, the habitat is somewhat fragmented because these small conservation areas are often interspersed with cattle ranches, and, in some cases, fencing . This is the case for most of the Northern Province, but not for the Waterberg Mountains area, where the unconserved areas are relatively undisturbed, mainly due to the rocky nature of the area.
The situation in Botswana and Zimbabwe is very different because the human population density is low and is restricted to small settlements. There are still large areas of continuous habitat remaining in these two countries. There are no protected areas in the Botswana portion of the ecoregion. In Zimbabwe, the most important protected area is Matopos National Park (425 km2). The Matobo Hills are an essential water catchment area and are known for their unique geological formations, dominated by many granite inselbergs, or kopjes, interspersed with caves. As many as forty raptor species are found here and over 85 mammal species have been recorded here, including small but well-protected populations of black and white (Ceratotherium simum) rhinoceros. Finally the region has great cultural and archaeological significance, including important rock paintings circa 5000 BC, and has been inhabited from the Stone Age to the present.
Types and severity of threats
The major land-use activities in the northern Province of South Africa are game and cattle farming. Game farming preserves the natural habitat whereas cattle farming can lead to its degradation. Cattle directly degrade the habitat by grazing and trampling plants and by exposing and compacting the soil, leading to soil erosion. Cattle can also lead to bush encroachment by reducing grass cover and subsequent fire frequency. These processes lead to reduced biodiversity within the area. The predatory and scavenging fauna of the bushveld are perceived as pests by farmers and routinely exterminated. Blackbacked jackals (Canis mesomelas), caracals (Felis caracal), and vulnerable Cape vultures (Gyps coprotheres) are common target species. Poisoned carcasses are a popular method of killing these species. Non-target species such as bat-eared foxes (Otocyon megalotis), aardwolves (Proteles cristarus), and aardvarks (Orycteropus afer) are often also killed.
Direct habitat loss is prevalent on the Springbok Flats, the most-threatened habitat within the ecoregion. The fertile clay soils of these flats are ideal for crops such as wheat, maize, and sunflowers. In addition to direct habitat loss, the agriculture in this area has had a negative impact on many bird species through the use of organo-chloride insecticides and herbicides, notably DDT. Direct habitat loss is also threatening the south of the ecoregion through the expansion of the Pretoria-Witwatersrand-Vereeniging complex. This "vaal triangle" is one of South Africa’s most densely populated industrial areas.
There are fewer threats to the north of the ecoregion in Botswana and Zimbabwe, where low-intensity goat and cattle farming create the principal impact. The removal of dead wood for firewood also negatively impacts obligate tree-hole nesting birds and small mammals. In large areas of Botswana and Zimbabwe, wildlife contributes significantly to the local economy. Wildlife utilization was originally mostly licensed trophy hunting, but is now increasingly oriented toward non-consumptive recreation and tourism. This trend should improve the conservation status in the north of the ecoregion.
There are four alien plant species that have invaded the Southern African bushveld. These are Jacaranda mimosifolia, Lantana camara, syringa (Melia azedarach), and white mulberry (Morus alba). The impacts of these invasive species here may not be as serious a threat as it is in other ecoregions in southern Africa (such as the Lowland Fynbos and Renosterveld ecoregion).
Justification of ecoregion delineation
The Southern African Bushveld, stretching from Bulawayo in the north to Pretoria in the south, combines White’s ‘Colophopsermum mopane woodland and scrub woodland’ and ‘South Zambezian undifferentiated woodland', and includes portions ‘Kalahari deciduous Acacia wooded grassland and deciduous bushland.’ Lying on a plateau, it has a higher elevation gradient than surrounding ecoregions to the west, north and east. The Highveld forms a distinct southern boundary, with even higher elevations between 1500 to 2000 metres.
This ecoregion forms part of larger complex of Caesalpinoid woodland ecoregions that support wet and dry miombo, mopane, thicket, dry forests, Baikiaea woodland, and flooded grassland habitats, among others. The dominance of Caesalpinoid trees is a defining feature of this bioregion (i.e., a complex of biogeographically related ecoregions). Major habitat types (e.g., mopane and miombo) and the geographic separation of populations of large mammals are used to discriminate ecoregions within this larger region. All of these ecoregions contain habitats that differ from their assigned biome or defining habitat type. For example, patches of dry forest occur within larger landscapes of miombo woodlands in several areas. More detailed biogeographic analyses should map the less dominant habitat types that occur within the larger ecoregions.
References and further reading
- Barnes, K. K.N., editor. 1998. The Important Bird Areas of Southern Africa. Birdlife South Africa, Johannesburg. ISBN: 0620234237
- Cole. M.M. 1986. The Savannas: Biogeography and Geobotany. Academic Press, London. ISBN: 0121795209
- Cowling, R.M., D.M. Richardson, and S.M. Pierce. 1997. Vegetation of Southern Africa. Cambridge University Press, Cambridge, UK. ISBN: 0521571421
- Du Plessis, M.A. 1995. The effects of fuelwood removal on the diversity of some cavity-using birds and mammals in South Africa. Biological Conservation, 74:77-82.
- Goldblatt, P. 1978. An analysis of the flora of Southern Africa: its characteristics, relationships and origins. Annuals of the Missouri Botanical Garden, 65:369-436.
- Hilton-Taylor, C. 1996. Red Data List of Southern African Plants. Strelitzia 4. National Botanical Institute, Pretoria. ISBN: 1874907293
- Hilton-Taylor, C. 2000. The 2000 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, UK. ISBN: 2831705657
- Hogan, C. Michael, Mark Cooke & Helen Murray. 2006. Waterberg Massif, Limpopo Province, South Africa. Lumina Technologies
- Johnston, H. and J.C. Tothill. 1985. Definition and broad geographic outline of savanna lands. Pages 1-14 in J.C. Tothill and J.J. Mott, editors. Ecology and Management of the World’s Savannas. Australian Academy of Science, Canberra. ISBN: 0858471213
- Low, A.B. and T.G. Rebelo. 1996. Vegetation of South Africa, Lesotho and Swaziland. Pretoria, South Africa: Dept. of Environmental Affairs and Tourism, Pretoria.
- Nix, H.A. 1983. Climate of tropical savannas. Pages 37-62 in F. Bourliere, editor. Tropical Savannas. Elsevier, Amsterdam. ISBN: 0444420355
- Scholes, R.J. and D.O. Hall. 1996. The carbon budget of tropical savannas, woodlands and grasslands. In: J.M. Melillo and A. Breymeyer, editors. Global Change: Carbon Cycle in Coniferous Forests and Grasslands. John Wiley and Sons, New York.
- Scholes, R.J. and B.H. Walker. 1993. An African Savanna: Synthesis of the Nylsvley Study. Cambridge University Press, Cambridge. ISBN: 0521419719
- Trollope, W.S.W. 1984. Fire in savanna. Pages 149-179 in P. de V. Gooysen and N.M. Tainton, editors. Ecological Effects of Fire in South African Ecosystems. Springer-Verlag, Berlin. ISBN: 0387135014
- Van der Meulen, F. 1979. Plant Sociology of the Western Transvaal Bushveld, South Africa: A Synaxonomic and Synecological Study. Dissertations Botanicae. Cramer, Vaduz. ISBN: 3768212203
- White, F. 1983. The Vegetation of Africa: A Descriptive Memoir to Accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa (3 Plates, Northwestern Africa, Northeastern Africa, and Southern Africa, 1:5,000,000). UNESCO, Paris. ISBN: 9231019554
- Wild, H. and A. Fernandes. 1968. Vegetation Map of the Flora Zambesiaca Area. Flora Zambesiaca supplement. M.O. Collins, Salisbury.
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