Mpumalanga Biodiversity Conservation Plan Handbook - bgis-sanbi

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CHAPTER 3 .......................... MPUMALANGA’S ECOSYSTEMS An ecosystem is a dynamic complex of plant, animal and microorganism communities and their nonliving environment, interacting as a functional unit (NEMA). Ecosystems operate at various scales; from a single wetland to an entire region such as a range of mountains. Groups of ecosystems with common characteristics at a landscape scale are called biomes. This chapter briefly describes Mpumalanga’s main ecosystems, with some notes on their functioning, diversity and ecological status. 3.1 TERRESTRIAL ECOSYSTEMS CHAPTER 3 - MPUMALANGA’S ECOSYSTEMS THE BIOMES Mpumalanga is a warm summer-rainfall province, containing three of South Africa’s nine biomes: grassland (highveld and escarpment hills), savanna (escarpment foothills and lowveld) and forest (south and east facing escarpment valleys). Descriptions of these biomes are useful in understanding the biodiversity and ecological characteristics of the Province (Table 3.1). A map of the biomes is included in Figure 3.1. 9 ECOSYSTEMS
MPUMALANGA BIODIVERSITY CONSERVATION PLAN HANDBOOK 10 Common Greenshank Tringa nebularia Most species are completely dependent on a narrow range of environmental conditions and the food and shelter offered by those conditions. Even small changes can have lasting and devastating effects on whole populations. Birds like the migrant greenshank are not rare but they are restricted to feeding in water between about 40mm and 120mm deep. TABLE 3.1 Extent of Mpumalanga’s three biomes. BIOME TOTAL SIZE (km 2 ) % OF REMAINING %TRANSFORMED MPUMALANGA NATURAL TRANSFORMATION Transformation refers to the removal or radical disturbance of natural vegetation, for example by crop agriculture, plantation forestry, mining or urban development. Transformation mostly results in a serious and permanent loss of biodiversity and fragmentation of ecosystems, which in turn lead to the failure of ecological processes. Remnants of biodiversity may survive in transformed landscapes. The MBCP transformation layer was created by merging the 1995 and 2000 National Land Cover maps. These maps were created from satellite images that had been classified (by the CSIR and ARC) into various land-use types, using remote sensing techniques. The MBCP transformation layer is the best available representation of lost natural habitat based on composite, six-year-old data. The composite layer was cross-checked against a false-colour satellite image taken in 2000, allowing mis-classified areas to be corrected. GRASSLAND Grassland defines itself: landscapes dominated by grass. Although grasses are the most visible plants, grasslands have a higher diversity than other herbaceous species, especially those with below-ground storage organs such as bulbs or tubers. These plants produce many of our spectacular wild flowers and contribute to biodiversity that is second only to the Cape Fynbos in species richness. Grassland species are particularly well adapted to being defoliated, whether by grazing, fire or frost. Repeated defoliation, within reason, does no real harm to such plants nor does it reduce productivity. African grasslands are particularly old, stable and resilient ecosystems. Most plants are perennials and surprisingly long lived, with very few annual species, which are the pioneer plants needed to repair disturbance. This makes our grasslands vulnerable to destruction by cultivation; once ploughed they are invaded by weedy pioneer plants that are mostly alien. Although many grassland plants do produce seed, very little germinates, most being used as vital food for their rich rodent and insect fauna. Mpumalanga’s grasslands are mainly found in the highveld above 1000m. These are cool, M P U M A L A N G A VEGETATION (km 2 ) Grassland 531 61% 298 44% Savanna 338 39% 255 25% Forest 40 0.5% 39 1% Total 874 100% 558 36% dry open landscapes, with rainfall of over 500mm/yr. Frost, hail storms and lightning strikes Biodiversity are common. It is the natural occurrence of fire and these other defoliating events that favour grassland plants over woody species and help maintain the open treeless character of grasslands. Grasslands have shallowrooted vegetation with a growing season limited to about six months of the year. The nongrowing seasons are characterised by cool and dry conditions, during which time most foliage is removed or killed by frost, and dies back to ground level. CONSERVATION PLAN HANDBOOK
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