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| The fynbos of the Western and Eastern Cape constitutes one of the world's six floral kingdoms, with eight protected areas proclaimed as World Heritage Sites in recognition of their global importance - over 69% of the 9 000 plant species in these areas occur nowhere else in the world. |
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| Pines, wattles, hakeas and gums are the major threats to the fynbos biome. Of these, pines and hakeas are nearly impossible to eradicate because they are so widespread and form dense and impenetrable stands. They also produce enormous quantities of winged seeds, especially after a fire, which are then spread over great distances. Australian wattles are extremely difficult and expensive to control. Most species are able to sprout after felling, while the seeds, buried in the soil, germinate by the thousands after a fire. |
The CSIR played a leading role in the establishment of the Working for Water programme, implemented by government in 1995. It has since grown into one of the world's biggest programmes on invasive species and their impact on biodiversity and water resources.
In 1945 Prof Chris Wicht, then officer-in-charge of the Jonkershoek Forestry Research Station outside Stellenbosch, identified the spread of exotic plant species as "one of the greatest threats" to the Cape vegetation in a landmark Special Publication of the Royal Society of South Africa. Today biological invasions are still regarded by the international community as the second largest threat to biodiversity after direct habitat destruction.
Attempts to control invasive alien plants in South Africa began in the fynbos biome as early as the 1930s. Initially control initiatives were conducted mostly to conserve natural vegetation and not for water or agricultural benefits.
These initial attempts were at best uncoordinated and erratic, with much effort and money wasted. For example, in 1980 the South African Journal of Botany reported that 47 years of control attempts on the southern Cape Peninsula were "almost totally ineffective for the first 35 years". These early efforts were followed by coordinated control programmes in the 1970s and 1980s and considerable effort went into developing sound, scientifically-based control options.
A global problem
In June 1982, the General Assembly of the Scientific Committee on Problems of the Environment (SCOPE) identified the invasive spread of plants, animals and micro-organisms by humans into areas far away from their centres of origin as a problem of global concern. The South African component of this international project led to the publication of a synthesis volume in 1986 entitled: The ecology and management of biological invasions in southern Africa.
According to CSIR chief researcher Dr Brian van Wilgen, most of this research attracted no more than academic interest: "It was only when researchers were able to demonstrate that invasions would have significant economic impact on water resources that the issue went beyond academic debate and into the realms of action."
By 1996, CSIR researchers had developed a model to estimate the impact of invasive alien trees on water resources in the fynbos biome. The model simulated five important processes: the occurrence of fire; the spread and establishment of alien plants after fire; rainfall to runoff rations; growth and changes between fires and effects of these processes on stream flow.
In an article published in the Journal of Applied Ecology, CSIR researchers predicted that the cover of alien plants would increase from an initial estimate of 2.4% to 62.4% over 100 years, decreasing stream flow from the catchment by 347 m³ per hectare. This is equivalent to 30% of the annual water supply to the City of Cape Town. Subsequent studies reaffirmed the findings that early investment in alien plant control made good economic sense. All these studies relied heavily on the model developed by the CSIR in 1996.
In 1995, the CSIR played a leading role convincing the newly-elected democratic government to create the Working for Water programme. The programme served the dual purpose of reducing the impact of invasive alien plants on water supplies, while at the same time providing employment for people in rural areas.
Facing the future
The Working for Water programme currently spends R600 million each year on providing over 20 000 jobs aimed at clearing invasive alien plants. However, even this is not enough and other solutions must be sought.
At present the programme invests in research on biological control agents that assists in the combat of invasive alien plants. The mechanical clearing of infestations by people is necessary, but will never succeed in clearing all invaded areas and maintaining them. According to Van Wilgen the challenge of holding onto the gains will depend on whether or not self-sustaining biological control solutions can be found for problem weed species. It will also depend on the degree to which landowners take responsibility for their own land, rather than relying solely on government to provide solutions.
For more information, read Dr Van Wilgen's article, The evolution of fire and invasive alien plant management practices in fynbos, published in the South African Journal of Science Volume 105 (2009).
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