State of terrestrial ecosystems: # 2

Current Land Condition:  

Figure 2.6 Map of alien infestation

Vegetation: Severe inroads into natural vegetation have been created by invasive species, an estimated 8% (10 million hectares) of South Africa having been invaded to some degree by a wide range of alien species (Versveld et al. 1998). Alien plant invasion is occurring in all seven of South Africa's biomes. Dense infestations (up to 14% of the area) are found in the species-rich Fynbos biome. Significant plant invasions are noted for each of the other six biomes, but comparable estimates of spatial extent are not available (e.g. Richardson et al. 1997). Invasive annual grasses (Milton et al. 1997) pose direct threats to the rich annual and bulb flora of the Namaqualand region (Succulent Karoo Biome). Overgrazing is seen as a main cause of veld degradation in the natural rangelands of South Africa (Bosch & Theunissen 1992; in Hoffman, 1997). Selection of palatable species by livestock in Karoo rangelands is strongly implicated in altering vegetation composition (Milton et al. 1997), and thus plant diversity.

Bush encroachment is the process which transforms a grass-dominated vegetation type into a woody species-dominated one. This is recognised as a very serious problem throughout Sub-Saharan Africa, because it means that large areas of grazing lands are lost (or reduced in capacity), and it transforms habitats and reduces species diversity. In 1956 it was estimated that almost 13 million hectares of veld in South Africa had been badly affected by bush encroachment, and by 1983 it was estimated that 33% of southern Africa's bush, scrub, and savanna vegetation, had been invaded and dominated by woody species. Although only a few species are regarded as problematic, bush encroachment can be rapid, and costly to control. The worst affected areas in South Africa are in the Northern Cape, the Eastern Cape, and the Northern Province.

Figure 2.7 Bush encroachment. From left to right: 10%, 50% and 75%. Source: Agricultural Research Council.

Soil degradation encompasses physical degradation (compaction, crusting , structural deterioration, erosion, desertification),, chemical degradation, (acidification, salinisation, sodicity and alkalination, nutrient depletion, pollution, toxicity); and biological degradation (decline in soil organic matter, loss of biodiversity, and soil sterility). It is estimated that water erosion affects 6.1 million hectares of cultivated soil in South Africa. Of this 15% is seriously affected, 37% moderately and the rest slightly. Wind erosion affects even more land, an estimated 10.9 million hectares of cultivated soil. Of this 7% is seriously affected, 29% moderately and 64% slightly. (LandCare Supplement, 1998). The estimated mean annual soil loss of 2.5 tonnes per hectare per year is severe, with the highest losses of up to 60 tonnes per hectare per year reported from unprotected pineapple fields (Schoeman & Scotney, 1987). Given that soil formation is estimated at 0.31 tonnes per hectare per year (van der Merwe & de Villiers, 1997), the rate of soil loss is at least eight times the rate of replacement. This situation is obviously unsustainable. In addition, over 2.5 million hectares of soil are estimated to be acidified. The only viable solution for alleviating soil acidity is the application of lime, although annual sales of liming materials indicate that the problem is not being adequately addressed (Beukes, 1997).

A number of largely qualitative statements regarding different aspects of soil degradation are summarized in Table 2.1 (Van Zyl, 1997).

Because of the complexity of land degradation and the difficulty of selecting objective indicators, the recently released report on Land Degradation in South Africa (Hoffman et al.1999) adopted a novel approach in compiling a "consensus map"f degradation in South Africa. Thirty four workshops were held throughout the country, in which 453 agricultural extension officers and resource conservation technicians participated. A comprehensive literature survey and several field trips contributed to the findings. From this study, the relative extent of degradation, as an index related to standard deviation, for soil and veld separately and combined, is given in Figure 2.8. Areas with steep slopes, low rainfall and high temperatures are significantly more degraded. The Northern Province, KwaZulu-Natal and the Eastern Cape are the provinces with the highest levels of degradation. Communal areas seem to have about twice the perceived level of land degradation of commercially managed rangelands, but the trend in many communal areas may be towards "underfarming"or less reliance on agricultural production, as other sources of income gain in importance. Fuelwood collection in communal areas remains a major pressure, which may be reduced by electrification schemes in rural areas (depending on the acceptability of the scheme pricing policy). While commercial systems have experienced land degradation to some extent, government support and input (scientific research and soil and vegetation conservation policies) have contained degradation rates appreciably.

Figure 2.8 Degradation map

Productivity: The 1.5 million hectares of plantation forests in South Africa have a combined output of 9 million tonnes of pulpwood every year. Wood consumption across the country amounts to about 10 million tonnes per year, a substantial fraction of this coming from plantation forests. The forestry industry contributes approximately 1.8% to GDP, and about 7% to manufacturing output (1997). In 1998, the industry generated net foreign exchange earnings of approximately R2.5 billion.

Agriculture contributed 4.5% to GDP in 1997, provided 1.2 million jobs, and earned the largest share of foreign exchange (approximately R11.5 billion). The most important commercial crops are maize (10 million tonnes produced annually), wheat (2.6 million tonnes), sunflowers (0.6 million tonnes), grain sorghum (0.4 million tonnes), and soya beans (0.2 million tonnes).

Figure 2.9 Prime agricultural land

A map indicating prime agricultural land is given in Figure 2.9. The current perception is that prime agricultural land is under pressure for conversion to other uses. A cut-back in the area of prime agricultural land will reduce the ability to support such large quantities of food and fibre crops.

Figure 2.10 Primary production for South Africa

Primary production is an indicator of the production capability of natural and transformed vegetation systems, under rainfed (not irrigated) conditions as shown in Figure 2.10 Schulze et al. 1997). Primary production is relatively low in the west of the country, where rainfall is also low, increasing towards the wetter eastern seaboard, and with relatively high production in the winter rainfall area of the Cape.

Figure 2.11 Maize yield estimation for South Africa

As maize is the most important crop, a comparable map showing its production potential is included for comparison (Figure 2.11).

Pollution and waste:  

Over 42 million cubic metres of general waste is generated every year across the country, with the largest proportion coming from Gauteng province (42%)(DWAF 1997). In addition, more than 5 million cubic metres of hazardous waste is produced every year, mostly in Mpumalanga and KwaZulu-Natal (due to the concentration of mining activities and fertiliser production in these provinces). The average amount of waste generated per person per day in South Africa is 0.7 kg. This is closer to the average produced in developed countries (73 kg in the UK and 0.87 kg in Singapore), than to the average in developing countries such as 0.3 kg in Nepal (DWAF 1997). A recent study investigating the disposal sites for general and hazardous wastes in South Africa showed that there are currently 540 sites across the country. At the current rate of disposal, it is predicted that over the next five years, the generation of waste will exceed landfill capacity in five of the nine provinces, by up to 67% (DWAF 1997).

By far the biggest contributor to the solid waste stream is mining waste (72.3%), followed by pulverized fuel ash (6.7%), agricultural waste (6.1%), urban waste (4.5%) and sewage sludge (3.6%) (van der Merwe & Vosloo, 1992).

These high volumes of waste and pollution are cause for concern. However, what is truly alarming is the proportion of waste (particularly hazardous waste) that does not receive proper treatment or disposal. Of the 5 million cubic metres of hazardous waste generated every year, less than 5% reaches hazardous waste disposal sites (DWAF 1997). Furthermore, the rate of increase in production of hazardous waste is estimated to be 2.6% per annum over the next 10 years (DWAF 1997).

>     Terrestrial Ecosystems: State #3

There is also information about Terrestrial Ecosystems in the following reports:
Metropolitan reports:
	Cape Metropolitan Council (1998 edition)		Durban Pilot Study
	Greater Johannesburg Metropolitan Council (1999 edition)		Greater Pretoria Metropolitan Council (1999 edition)

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Last update: October 1999