Overview of chapter
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South Africa has one of the world's greatest diversity of plant and animal species contained within one country, and is home to many species found nowhere else in the world. Terrestrial resources are rapidly disappearing however, due to conversion of natural habitat to farmland, forestry, human settlement, and industrial development. Some species are under threat from over-collection for medicinal, ornamental, and horticultural purposes.
Invasion by alien species of plants and animals is a major problem in South Africa. Alien organisms can replace large numbers (even whole populations) of native animals and plants, and alien plants use greater quantities of scarce water resources.
Degradation of vegetation and soils is also a widespread problem in South Africa. Rapid population growth and inappropriate government policies in the past encouraged cultivation in unsuitable areas, and use of poor agricultural methods to produce sufficient food.
Recent policies, international conventions, and community-based initiatives being carried out are aimed at improved conservation and more sustainable use of natural resources in future.
Authors: Barnard Dr R,
Newby T, ARC- Institute for Soil, Climate & Water
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South Africa has the third highest level of biological diversity in the world, with 7.5% of the worlds vascular plants, 5.8% of the world's mammal species, 8% of the world's bird species, 4.6% of the world's reptile species, 16% of marine fish species and 5.5% of the world's recorded insect species.  |
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This high level of diversity is due to the broad range of climatic, geological, soil and landscape forms found in South Africa. However, many species are threatened, and extinction rates in South Africa are high by global standards.
Most of the land area (86%) is used for crop cultivation or grazing of livestock. Less than 10% of the area is conserved. South Africa is a semi-arid country, and drought and desertification are real threats to food security.
Terrestrial ecosystems are very complex, and research has only been able to cover a few aspects. It is not fully known what the impacts of extinction are, or what might happen if certain ecosystem processes are interfered with: these impacts are of relatively recent origen, and the consequences sre yet to play out.
For more background information about terrestrial ecosystems, read this section .
Rapid population growth has led to urbanisation, intensification of agricultural production, and industrialisation, in order to meet the demand for food, energy, and other commodities. These processes impact terrestrial ecosystems, through degradation, alteration of processes, or transformation. The increase in mobility of the human race due to modern transportation methods, has resulted in the introduction (both intentional and unintentional) of many non-native (alien) species. In some cases these species have become invasive, i.e. they have dominated the natural vegetation, and place an additional burden on already scarce resources, such as water.
Government policies cause changes to terrestrial ecosystems, in both positive and negative ways. For example, nature conservation laws have contributed to protection of species and habitats, preserving populations of species, the wilderness experience, enhancing quality of life, and slowing the rate of extinctions. On the other hand, government policies which encouraged monoculture and intensive use of agrochemicals have resulted in over-use of the land, and degradation of vegetation and soils. Policies which forced large numbers of people off their land and into the former "homeland" areas resulted in intense demand for natural resources in these areas (land for agriculture, wood for fuel, and space for housing, for example), and alienated people from the concept of conservation.
International demand for resources such as timber, and for biological resources such as wild animals, certain types of plants, and products such as elephant ivory and rhino horn, also cause changes to terrestrial ecosystems. In some cases, the combination of domestic and international demand drives over-use (exploitation) of resources, and has caused many species to become endangered or extinct. International pressure has also caused a shift away from harvesting of timber from natural forests, to the expansion of plantation forestry, which on the one hand prevents further destruction of natural forests, and the associated loss of biodiversity; whilst on the other hand contributes to the spread of alien vegetation, places a heavy demand on water resources, and contributes to loss and fragmentation of natural habitats.
For more information about the drivers of terrestrial ecosystem change, read this section.
Population growth, and industrialisation, urbanisation, and intensive agricultural and forestry production cause large amounts of waste and pollution to be generated. This places pressure on the environment in terms of suitable waste disposal sites, pollution, and changes to the atmospheric composition, with knock-on effects for climate stability. Population growth also leads to expansion of agriculture to meet the demand for food. This means that areas of natural habitat are converted to other land uses, either in large sections, or piecemeal, fragmenting the natural habitat. This impacts on the number and types of species that are found there, and the key ecosystem processes that support life, such as water quality, and nutrient cycling, may be impaired. Expansion of agricultural activities into unsuitable areas, together with bad land-use practices (such as over-use of agrochemicals, monoculture, ploughing down a slope), result in soil degradation and erosion.
Exploitation of resources can lead to deforestation and bush encroachment. These processes change the vegetation structure, and the type and number of animals that can be supported. Collection of plant material for the medicinal and horticultural trades, reduces the abundance of certain species in the wild, and has led to extinction of some. Alternatively, production of flowers for the international market, and game farming for meat, tourism and trophy hunting, can encourage preservation of natural habitats, and increase the number and type of species that are found there.
Changes in the climate which result from atmospheric pollution, can alter the distribution of species and communities. Each organism is adapted to a certain set of conditions, and when these conditions change (i.e. it gets warmer, or colder, or wetter), the organisms either die off, or if possible, migrate to an area more suitable. With so little of South Africa remaining as natural habitat, it may be difficult for organisms to move to more suitable areas, and extinctions will become more frequent.
Alien invasive organisms put pressure on terrestrial ecosystems because they dominate the indigenous species. Populations of native species may be less able to reproduce, or to fulfill their ecological role, and in some cases this is so extreme that native species have become locally and globally extinct. Alien invasive plants are a particular problem in certain parts of South Africa because they use more water than the natural vegetation. This means there is less water available for the natural vegetation and animals, for human consumption, and for irrigation and industrial uses.
For more information about the pressures on terrestrial ecosystems, read this section .
Twenty five per cent of South Africa's land area has been transformed, of which 13% is for cultivation of crops, 1.5% for forestry, and 2.5% to settlements. Five per cent has been degraded, and only 6% is under formal protection.
Over 8% of South Africa has been invaded by alien vegetation, and millions of hectares are affected by bush encroachment. Five per cent of soils are affected by water erosion, and the average soil loss is 2.5 tonnes per hectare per year, with a maximum of 60 tonnes per hectare per year. This is more than eight times the rate of soil formation, and clearly unsustainable.
South Africa has two internationally recognised biodiversity "hotspots", the Cape Floral Kingdom and the Succulent Karoo. In addition, seven of the eight southern African hotspots are wholly or partly located in South Africa. Hotspots are areas of high species richness and species diversity, as well as high levels of endemism. A high proportion of the terrestrial vertebrate fauna and the flora of South Africa is preserved in the country's582 public and private nature reserves in the form of breeding populations, with a few exceptions. However, 10% of South Africa's mammal species are threatened, 2% of its bird species, 12% of its reptiles species, 16% of its amphibian species, and 36% of its freshwater fish species. It is also estimated that the total number of threatened plant taxa doubled between 1980 and 1995 (Siegfried 1989).
For more information about the state
of terrestrial ecosystems in South Africa, read this section.
Transformation and fragmentation of natural habitats changes the number and type of species that occur there, and can disable the vital ecosystem processes that support growth. Changes in animal species composition can change the vegetation composition, because different animals choose different plants to feed on. But changes in vegetation can also lead to changes in animal species, because there may be more or less material available for food, nesting, and camouflage. We do not fully know how each species functions within its community or habitat, and therefore cannot predict what will happen when some species are lost and others are gained. However, most of the changes in species composition that have been studied, show negative impacts for the system.
The introduction of alien plant species (either by accident or plan) has serious implications for water availability. In total, South Africa's forestry plantations use about 3% of the available surface water, and alien plants use 7% of the available surface water, every year.
Production pressures on terrestrial ecosystems that result in degradation of the vegetation and soil, leave the land less productive in future. In 1970 there was 0.86 hectares of agricultural land available per person. This decreased to 0.5 hectares per capita in 1980 and it is estimated that this will decrease further to 0.2 hectares per capita by 2020. This has serious implications for income generating exports, and domestic food security.
Changes in distribution of species and communities due to climate change may increase or decrease agricultural production capacity, may contribute to species extinctions, and may encourage the spread of alien organisms. The extent of each of these is uncertain at this stage.
For more information about the impacts on terrestrial ecosystems, read this section.
South Africa has ratified several international conventions which aim to improve the sustainability of terrestrial ecosystems internationally. Examples include the Convention on Biodiversity, the Convention to Combat Desertification, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
South Africa also has developed policies and passed a number of laws which promote conservation and sustainable use of natural resources (see Conventions and Agreements).
Other initiatives include schemes to reduce grazing and cultivation pressures, restore and maintain healthy soils and promote sustainable management of plantation forests.
For more information about the response to changes in terrestrial ecosystems, read this section.
The population is still growing, and therefore the demand for resources will continue to increase. Loss of habitats and resources will continue, unless control measures are implemented and adhered to. For example, formalisation of the trade in medicinal plants, through development of nurseries and commercial farms to meet demand, will create economic and social upliftment, whilst halting biodiversity loss and habitat transformation. The cut flower industry and commercial game farming are successful examples of formal exploitation of natural resources.
Involvement of communities in decision making and sharing of benefits from conservation areas, together with education, extension and research, and a balance between addressing social and environmental issues, will enhance feelings of ownership, and contribute to the success of schemes to promote sustainable development.
For more information about the outcomes on terrestrial ecosystems, read this section.
There are linkages between terrestrial ecosystems and some of the other issues addressed in this report.
To find out what these linkages are, read this section.
Good databases exist on agricultural and forestry statistics, and good inventories of plant and animal species exist. However, on-going monitoring of change in terrestrial ecosystems, and in particular quantitative data on the extent of degradation and land transformation, are priorities for further research.
For more information on data issues related to terrestrial ecosystems, read this section.
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There is also information about Terrestrial Ecosystems in the following reports:
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Metropolitan reports:
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Last update: October 1999
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