The underlying geology of a region has an intimate link with the flora and fauna supported by the soils derived from the rocks. The distribution of vegetation and plant communities is more varied in the south eastern savannahs, of which the Kruger to Canyons Biosphere is a part, than other African savannahs.
This is because the major geological structures have a north-
Natural avenues have been created for species migration both north-
The highest levels of species richness occur along the Afromontane belt. The Escarpment and eastern savannahs combine the altitudinal and climatic variations with the water catchment to underwrite this diversity.
The geological heritage of the area has also has a decisive impact on climate. The local altitudinal range is from 200m to 2,050m above sea level. Rainfall increases with proximity to the Great Escarpment. Annual levels vary from an average of 400mm per annum in the savannah areas in the east up to 3,000mm per annum in some areas in the south and west. These climatic variations further add to the increase in ranges of habitats which favour great species diversity. The area has very high levels of biodiversity and endemic (uniquely local) species as a consequence.
The underlying rock types also determine the nature of the soil that breaks down from them. In broad outline the younger surface of dark brown loams derived from the basalts today form Knobthorn-
The older exposed surfaces have more sandy soils derived from granite, and yield woodlands dominated by the Combretum species of leadwood and the bushwillows. These in turn impact the species of game that inhabit each ecozone, from the browsers and grazers that prefer each habitat to the carnivores that prey on them. The two main geological formations on the escarpment, Black Reef Quartzite and Malmani Dolomite, have 78 and 31 endemic plant species respectively (Matthews, 1991).
South Africa's eastern savannahs held the last complete savannah ecosystem still intact by the end of the nineteenth century, despite intense pressure from hunting and the cattle and mining industries.
By the third quarter of the twentieth century, complete balkanisation of this system had occurred with environment degradation and consequent species loss caused by the proliferation of fences and alternate land use practices.
However, a commensurate increase in environmental awareness and the need to extend protection to ecologically vital areas led to new theories in conservation centred on sustainable human land use.
Recent advances in ecology and landscape history and the social sciences have clearly indicated that nearly all the landscapes we see have been profoundly influenced by human activity in the past. Thus even the most ‘natural-
Seeking to maintain these areas in their current state, thus attempting to sustain (or restore) the existing biodiversity is also a cultural response– a purposeful intervention by people to maintain something they value.
The intensive occupation by humankind of the eastern savannahs has been the dominant factor in recent centuries in shaping the ecology of the region. The past hundred and fifty years have seen huge ecological transformations imposed on the local landscape.
Vast areas of montane grasslands have been converted to exotic forest plantation and hundreds of thousands of hectares of bush savannah have been rendered unsuitable for plains game and rare ungulate species by, from a sustainability perspective, inappropriate land use and management practices.
The effect of these transformations has been the local extinction of numerous mammal species and a concurrent loss in the overall genetic pool of locally adapted species. Hemingway ruefully commented on Africa in the 1930’s that "Africa is a continent which ages quickly once we come to it". By then the first reserves had been declared in an effort to mitigate the habitat destruction.