Location and General Description
Part of White’s (1983) Tongoland-Pondoland Regional Mosaic, this ecoregion is found alongside the numerous rivers of the Eastern Cape and KwaZulu-Natal Provinces of South Africa. Some of the more prominent rivers include the Tugela Basin, just north of the urban center of Durban, and the mBashe, Kei, and Great Fish Rivers of the Eastern Cape. Many of the rivers of this ecoregion have deeply incised channels, as they drain the Drakensberg Mountains. While it generally occupies the deeper river valleys in the south, in the north the ecoregion is most extensively developed in low-lying country (White 1983). A narrow band of KwaZulu-Cape Coastal Forest separates this ecoregion from the sub-tropical waters of the Indian Ocean to the east, and most of it is surrounded by the Drakensberg Montane Grasslands, Woodland and Forest ecoregion.
The rifting and break-up of Gondwana, and subsequent cycles of uplift and erosion have shaped the landscape of this region. Following the establishment of an effective drainage system, these processes formed the Great Escarpment, which separates the elevated interior of Southern Africa from the coastal margins (WWF and IUCN 1994). The vegetation of this ecoregion spans a range of geological formations from basement granites, to schists, gneisses and lavas (basalt and dolomite intrusions), and to various sedimentary strata, including marine sediments from the Cretaceous and Cenozoic periods. Clay and lithosol soils of the Cape Beaufort group predominate (Low and Rebelo 1996. Maputaland-Pondoland Bushland and Thicket is generally restricted to deep, well-drained soils (Cowling 1984) that are usually moderately to highly leached (Moll 1976).
The ecoregion experiences a seasonal, relatively dry climate. For most of the ecoregion, rainfall is below 800 mm per annum and decreases to 450 mm in parts of the southern areas. Up to 75 percent of the annual precipitation falls within the warm summer months between October and March (Moll 1976). Temperatures range from 12o to 26oC. The ecoregion is virtually frost-free, largely due to its close proximity to the sea.
Maputaland-Pondoland Bushland and Thicket is distinguished from other African thicket types by a predominance of evergreen sclerophyllous plants, and is differentiated from the adjacent Albany Thicket ecoregion to the south by its relative paucity of succulent trees and shrubs (Everard 1987). It generally consists of a closed canopy formation up to 6 m in height and frequently forms an impenetrable tangle of spinescent shrubs, low trees and vines. It is generally not divided into strata and usually does not have a pronounced herbaceous or grass layer (Low and Rebelo 1996). Characteristic woody species include Diospyros dichrophylla, Euphorbia triangularis, Rhus dentata, and Senecio deltoides. Other more widespread common species include Putterlickia pyracantha, Rhoicissus tridentata, Grewia accidentalis, Phyllanthus verrucosus, and the grass Panicum maximum.
Rainfall appears to be the most important determinant of community composition and structure of this vegetation type. This ecoregion appears to replace forest in areas that are protected from fire, but where rainfall is relatively low. Furthermore, pronounced floristic and physiognomic gradients are evident in the ecoregion. Height and deciduousness decrease towards the south, while succulence, sclerophylly and spinescence increase (White 1983); this is a pattern that closely mirrors the rainfall gradient of the area. In areas north of the Tugela River, where rainfall is higher and more predictable, many Zambezian tree species are evident, although they seldom dominate the landscape. These include Acacia sieberana, Albizia versicolor, Combretum spp, Ficus sycamorus, Sclerocarya caffra, Terminalia sericea and Ziziphus macronata. Towards the south, the highly erratic distribution of rainfall requires that plants be able to utilise soil moisture whenever available; succulence, sclerophylly, deciduousness and spinescence are some of strategies adapted for coping with such environmental conditions.
The area broadly falls into White’s (1983) Tongoland-Pondoland evergreen and semi-evergreen thicket and is commonly termed subtropical "transitional" thicket (Cowling 1984; Everard 1987), since it traverses a number of formal biomes (Low and Rebelo 1996). Furthermore, the ecoregion is situated in one of the most diverse areas in Africa and therefore shows significant floristic overlap with major vegetation types such as Afromontane forest, coastal forest, broadleaved Zambezian woodland and Karoo shrubland (White 1983). This ecoregion therefore demonstrates a high level of floristic diversity and complexity, although floral endemicity is low (Everard 1987; Low and Rebelo 1996).
Cowling (1983) has shown that the thickets of this ecoregion have similar plant diversity to other vegetation types in the southeastern Cape and are in fact as species-rich as the fynbos formations, which are world renowned for their outstanding diversity. Between 6,000 and 7,000 plant species occur in the ecoregion, with more than 49 species per 100 m2 recorded in the mesic Kaffrarian thicket areas (Everard 1987). However, it should be noted that this diversity includes the grassland, Afromontane forest, coastal, sand and swamp forests, palmveld and aquatic communities found within the ecoregion. Species endemism is relatively low, with much of this endemism being restricted to succulent genera such as Euphorbia, Crassula, Delosperma and Aloe. Cycads are fairly well represented in this ecoregion with the Kei cycad (Encephalartos princep), Bushman’s river cycad (E. trispinosusi), Alexandria cycad (E. arenarius) and the Albany cycad (E. latifrons) being almost or totally restricted to the ecoregion (Goode 1989). Apart from the proximity to a range of vegetation types, Gibbs Russel and Robinson (1981) reason that these low levels of endemicity may be due to selection pressures, particularly climatic instability, which has produced a flora where generalist genotypes are favored.
The overall faunal diversity is moderate to poor. Because many of the species move freely between the ecoregion and surrounding vegetation types, the number of endemic animal species is also relatively low. While many of the mammal species that historically occupied this ecoregion are still represented, numbers have generally declined quite markedly. In some cases species have become locally extinct (Smithers 1983); this is particularly true for larger carnivores such as the leopard (Panthera pardus), which, although still present, now generally occupies the less accessible gorges and crevices of the area. Smaller predators are more characteristic of the ecoregion. These include serval (Felis serval), caracal (F. caracal), large spotted genet (Genetta tigrina), honey badger (Mellivora capensis) and the white-tailed mongoose (Ichneumia albicauda). The black-backed jackal (Canis mesomelas) was historically found extensively throughout the area but intensive control measures have resulted in an enormous decline (Smithers 1983). Marsh (Atilax paludinosus) and large grey mongoose (Herpestes ichneumon), as well as the spotted-necked (Lutra maculicollis) and Cape clawless otter (Aonyx capensis) inhabit the river courses and valleys of the ecoregion, although the Cape clawless otter often wanders far from permanent waters in search of new feeding grounds (Smithers 1983).
Ungulates are not particularly well represented. However, both the critically endangered black rhinos (Diceros bicornis) (Hilton-Taylor 2000) and white rhinos (Ceratotherium simum) are represented (IUCN 1987). Bush pigs (Potamochoerus larvatus) are relatively common, preferring valley bottoms with dense vegetation and soft soils (Kingdon 1997), while blue duiker (Cephalophus monticola) is mostly confined to forest, moist thickets and dense coastal bush (Smithers 1983). Other antelope of the ecoregion include bushbuck (Tragelaphus scriptus), greater kudu (T. strepsiceros), common duiker (Sylvicapra grimmia), mountain reedbuck (Redunca fulvorufula) and eland (Taurotragus oryx).
While sub-specific species richness is relatively high, only two near endemic mammal species are found in this ecoregion. These are the endangered giant golden mole (Chrysospalax trevelyani) (Hilton-Taylor2000), which occupies deep-soiled areas in the forests and thickets of the Eastern Cape, and the Natal red rock rabbit (Pronolagus crassicaudatus), a species that inhabits the steep rocky hillsides of the eastern seaboard of South Africa and southern Mozambique (Kingdon 1997).
Because of the porous boundaries, this ecoregion boasts a great variety of species, all of which are shared with surrounding ecoregions and habitats. Two near-endemics are only marginal to the ecoregion. The chorister robin (Cossypha dichroa) is mostly associated with forests but is found within the geographic borders of the ecoregion, while the forest canary (Serinus scotops) is found more frequently in thicket vegetation. In the Eastern Cape it is common in the dry euphorbia-dominated communities on the upper south-facing slopes of river valleys.
The Cape vulture (Gyps coprotheres, VU) is also found in the ecoregion. While this species forages mainly over grassland and woodland it is dependent on high cliffs for breeding. Collywobbles vulture colony, found along the cliffs of the convoluted gorge formed by the mBashe River has been identified as an Important Bird Area by Barnes (1998). At least 60-90 breeding pairs (up to 250 individuals) of this species are known to roost at this site, although up to 300 breeding pairs have been recorded here at times (Barnes 1998). Another globally threatened bird found in the ecoregion is the spotted ground thrush (Zoothera guttata EN). Although the Knysna warbler (Bradypterus sylvaticus, VU) does not occur in the ecoregion itself, this species is restricted to highly fragmented forest patches in the coastal regions of the Eastern and Western Cape. Some of these habitats may be completely surrounded by Maputaland-Pondoland Bushland and Thicket. Threats to or negative impacts on this ecoregion may thus adversely affect these forest patches, and therefore threaten the survival of this bird species.
Amphibian and reptile diversity and endemism are fairly high. Two of the reptiles near-endemic to the ecoregion (Bradypodion thamnobates and Kinixys natalensis) are regarded as locally rare (Hilton-Taylor 2000), whereas two of the amphibians Hyperolius pickersgilli and Leptopelis xenodactylus are regarded as vulnerable, and Cacosternum poyntoni is assessed as data deficient (Hilton-Taylor2000).
This ecoregion is naturally fragmented since it occupies only the narrow river valleys running through the Drakensberg Mountain foothills. In addition, the Eastern Cape and KwaZulu-Natal have been subject to a long history of human occupation (Hall 1988), and until recently contained the Ciskei and the Transkei, two of the Apartheid-designated "Homelands". For almost a century, more than 80 percent of South Africa’s population was forced to live on less than 15 percent of the country in the various homelands scattered throughout the country. Such high densities have resulted in a high degree of landscape transformation, especially as a result of cultivation and high livestock densities.
Due to the large human population throughout the ecoregion, the ecoregion’s fauna has suffered considerably and many populations have been severely depleted through overexploitation, illegal hunting or extermination. However, only about 50 percent of the vegetation and habitats of the ecoregion have been transformed (Low and Rebelo 1996), and hence the habitat itself is not under severe threat. This is partly due to the fact that bushland thicket largely occupies the steep slopes of river valleys, which are generally unsuitable for cultivation and often less accessible to livestock. In addition, thicket is known to encroach into grasslands in the absence of large browsers, overgrazing or ineffective fire regimes. This is clearly occurring in the Drakensberg Montane Grasslands, Woodlands and Forests ecoregion, where the absence of large browsers such as kudu and black rhino, in combination with intensive grazing by ostriches and goats, is allowing significant thicket encroachment. While such thicket is secondary and would clearly lack a full suite of the ecoregion’s characteristic species, there is the possibility of biologically interesting bushland thicket developing over time.
Roughly 7.5 percent of this area is conserved (WWF and IUCN 1994). Twelve nature reserves and protected areas are officially recognized. Proclaimed in 1973, the Andries Vosloo Kudu Reserve has recently been greatly expanded to include the newly established Sam Knott Nature Reserve and the Double Drift Nature Reserve. Together these three protected areas make up a total area of 450 km2 (Stuart and Stuart 1992). The vegetation consists largely of bushland thicket as well as forest, Karoo shrub, open grassland and euphorbia "forest". Endemic plant species of interest include Pachypodium bispinosum, P. succulentum and Encephalartos trispinosus (Greyling and Huntley 1984). Black rhino, buffalo, eland and warthog (Phacochoerus africanus) have been reintroduced, while natural populations of greater kudu, bushbuck, common duiker and springbuck (Antidorcas marsupialis) as well as chacma baboons (Papio hamadryas and vervet monkeys (Chlorocebus aethiops) are common.
The Oribi Gorge Nature Reserve, which protects a spectacular section of the Mzimkulwana River in KwaZulu-Natal covers a range of vegetation types from forest, riverine thicket, mixed evergreen and deciduous thicket, evergreen sclerophyllous shrubland and open grassland. 268 bird species are known to occur in the reserve and raptors are particularly well represented. The Thomas Baines Nature Reserve consists mainly of hilly country covered by a mixture of bushland thicket, mixed grassland and fynbos and is traversed by the Palmiet River. The endemic plant Oldenburgia arbuscula occurs here (Greyling and Huntley 1984). Of the 42 mammal species found in the reserve, prominent animals include eland, buffalo, bushbuck, mountain reedbuck, as well as black wildebeest (Connochaetes gnou), and bontebok (Damaliscus dorcas dorcas) (Hilton-Taylor2000).
Types and Severity of Threats
Scattered in the river valleys between highly populated rural areas, this ecoregion is directly or indirectly threatened by agricultural activities associated with land clearance for cultivation, and overgrazing as a result of extremely high stocking densities (World Bank 1993). While much of the southern portions of the ecoregion are found on steep slopes that are unsuitable for cultivation, the northern areas are found on more even ground, where extensive cultivation of staple and cash crops such as sugar cane, bananas, tea, maize, and other subtropical crops occur (WWF and IUCN 1994). In addition, increased land pressures due to rapidly expanding populations, is resulting in marginal or unsuitable land being cleared, which obviously places the remaining vegetation of the ecoregion under considerable threat.
Parts of the bushland thicket vegetation suffer from overgrazing, mostly from goats, sheep and cattle. As opposed to other habitats, cattle farming generally has limited impact on this ecoregion as these animals’ activities are mostly restricted to grasslands. Their grazing and trampling can encourage thicket growth by reducing grass cover. However, the opportunistic feeding patterns of sheep and goats can have a severe impact on both the composition and productivity of this ecoregion. In addition, both these animals are known to be more destructive than cattle at higher stocking densities (Skead 1988). High livestock densities also pose considerable threat to wildlife, since high numbers of domesticated animals generally cause a displacement of game, as there is less suitable habitat available. Furthermore, wild predators and scavengers such as the black-backed jackal, caracal, leopard and the Cape vulture have been eradicated by livestock farmers who see these animals as a threat to their livelihoods. Poisoned carcasses are often used for this purpose; this method is indiscriminate and therefore poses considerable threat to all predators and scavengers. Poaching and illegal hunting are further reducing wildlife populations.
Unsustainable medicinal plant harvesting poses significant threat to several plant species. In a survey of a region in KwaZulu-Natal, all respondents acknowledged using medicinal plants (Ellis 1986). The area covered by the ecoregion experiences amongst the highest concentrations of harvesting in South Africa, with more than 1,030 species collected in KwaZulu-Natal alone (Hutchings et al. 1996). Many of the plants are collected in great numbers, and since most are either bulbs or are strip-barked, such collecting activities destroy the entire plant, not just portions of an individual.
A further threat to the integrity of this ecoregion is the invasion of natural vegetation by alien plants. Some of the more pervasive species of this ecoregion include Lantana camara, Psidium guajava, Rubus spp., Solanum mauritianum, Acacia Cyclops and A. mearnsii. The last has been commercially planted on a vast scale, and A. dealbata has also invaded along watercourses.
Several large urban centers fall within the geographical boundaries of this ecoregion, namely, Durban, Umtata, King William’s Town, East London and Grahamstown. Durban and East London are found along the coast; their major impact on the ecoregion would therefore be in terms of gradual population expansion and localized impacts of industrial activities and pollution. King William’s town, Umtata and Grahamstown potentially have greater impacts as they are found further inland and are mostly surrounded by bushland thicket vegetation. Being located higher in the catchment areas, pollutants and wastes produced by these centers may adversely affect habitats and biota in the downstream reaches of the ecoregion.
One of the threats presently of great concern to many environmental organizations is the Coega Project, which is one of the government’s Spatial Development Initiatives (SDI) planned at promoting economic activity (SDI 2000). The Coega Industrial Development Zone will be situated 20 km east of Port Elizabeth, straddling the Coega River and occupying a total area of 170 km2. Construction of the zone, including such ventures as three steel industries and a deepwater port were scheduled to begin in the fourth quarter of 2000, and will take up to 30 years to complete. As part of this project road development is also planned. A new toll road that will join Port Edward in KwaZulu-Natal with Port St Johns on the Wild coast is presently under consideration, and if constructed , would have an impact on the biota and habitat of this ecoregion.
Justification of Ecoregion Delineation
This area forms a part of the ‘South African evergreen and semi-evergeen bushland’ vegetation unit of White (1983), although it more closely follows the ‘valley thicket’ vegetation type of Low and Rebelo (1996). It contains transitional Tongoland-Pondoland and Afromontane affinities, and forms part of the Tongaland-Pondoland Center of Plant Diversity (WWF and IUCN 1994), recognized as one of the most floristically diverse areas in Africa.
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Prepared by: Karen Goldberg and Alliette Frank
Reviewed by: In progress