Location and General Description
The Southern African Bushveld is part of the vast savannas that cover much of southern Africa. There is little in the way of endemic flora or fauna, but the charismatic large mammals and rich bird life typical of African savannas are present. The rugged Waterberg Mountains contain the highest levels of species richness and endemism in the region, and are noted for their reptile 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 activity in the bushveld and has led to the establishment of many small nature reserves and private game parks in the area, which enhance the conservation status of this ecoregion.
The Southern African Bushveld belongs to the vast savanna biome, the dominant vegetation of Africa, occupying 54 percent of southern Africa (Cowling et al. 1997), 60 percent of sub-Saharan Africa (Scholes and Walker 1993), and 12 percent of the global land surface (Scholes and Hall 1996). Savannas are generally defined as a continuum of vegetation types with trees and grasses as their main constituents (Scholes and Walker 1993). 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 m to 1,100 m).
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 (1,500 to 2,000 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" (Cowling et al.1997) 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 infertile. The savannas characteristic of this moister environment are termed "moist broad-leafed savannas" or "semi-deciduous forests" (Cowling et al. 1997) and include the Zambezian Baikiaea Woodland and the Southern Miombo Woodland ecoregions. The low-lying Limpopo 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 all savannas worldwide is climate, specifically, a hot wet season of 4 to 8 months in duration, and a cool dry season for the rest of the year (Cole 1986). 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 mm to 750 mm (Nix 1983), with a slightly higher average (650 mm to 900 mm) in the Waterberg Mountains (Low and Rebelo 1996). The highveld plateau to the south forms a ridge running east to west, and provides shelter against cooler air masses from the south (Van der Meulen 1979). 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 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 of between 700 m to 1,100 m. The soils of this plateau are mostly coarse, sandy and shallow, overlying granite, quartzite, sandstone or shale (Low and Rebelo 1996). 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 1,200 m to 1,500 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. (Low and Rebelo 1996).
The ecoregion is well-drained by the Limpopo and Olifants Rivers. 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 watershed area and drains the eastern part of the ecoregion. The two rivers converge before flowing into the Indian Ocean, just north of Maputo in Mozambique.
Cowling et al. (1997) 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. (1997) 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). 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 (Cowling et al. 1997). Towards the Tuli block in northern South Africa, C. mopane becomes less monodominant and is intermixed with other tree species such as Acacia tortilis and A. mellifera (Wild and Fernandes 1968). The "mixed savanna" of Cowling et al. (1997) varies from a dense, short bushveld to an open tree savanna.
To the north of the ecoregion (around Bulawayo in Zimbabwe) the vegetation turns into tree savanna about 6 m in height with a good grass cover. Hyparrhenia filipendula and H. dissolute 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 (Low and Rebelo 1996). 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 species. The savanna surrounding the Waterberg Mountains is characterized by African beachwood (Faurea saligna), common hookthorn (Acacia caffra), red seringa (Burkea africana), Terminalia sericea, and Peltophorum africanum. The rugged, rocky slopes of these mountains are dominated by white seringa (Kirkia acuminata), stemfruit (Englerophytum magalismontarum), Combretum apiculatum, C. molle, and common sugerbush (Protea caffra).
In principle, the conservation status of the Southern African Bushveld is good. 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 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. 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 (1996) estimate that 60 percent of this veld type has been transformed 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 (Cowling et al. 1984). About 9 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. 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 (Low and Rebelo 1996).
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 catchement 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, 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) (Hilton-Taylor 2000) 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 DDT (Barnes 1998). 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 (Cowling et al. 1997).
There are fewer threats to the north of the ecoregion in Botswana and Zimbabwe, where low-intensity goat and cattle farming create the major impact. The removal of dead wood for firewood may also negatively impact obligate tree-hole nesting birds and small mammals (du Plessis 1995). 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 exotic 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 is not 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 (1983) ‘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 1,500 to 2,000 m.
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.
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Prepared by: Amy Spriggs
Reviewed by: In progress