Cost-benefit analysis of alien vegetation clearing for water yield and tourism in a mountain catchment in the Western Cape of South Africa

Economic analysis is used to assess the costs and benefits of restoration following clearing of invasive alien trees in the floristically rich Fynbos mountainous area near Franschhoek, Western Cape of South Africa. The Groot Drakenstein, Franschhoek and Jonkershoek mountains receives more rainfall than the surrounding areas and is an important source of water for the city of Cape Town. The costs of alien invasive plant removal, gully-erosion repair and reseeding with indigenous plants are considered in a case-study cost-benefit analysis of restoration, in terms of the water and tourism benefits derived. Three different options of restoration (comprehensive, moderate, basic) were analysed under three different economic scenarios (optimistic, realistic, pessimistic) and the costs of which have been weighted up against the income derived from the supply of water and tourism. The results have shown that despite the high costs of restoration, the basic restoration option costs were out-weighed by the water and tourism benefits derived. This was also true of the moderate restoration option, when evaluated under the optimistic scenario and using an 8% discount rate, or a 3% discount rate under any scenario. However, this was not the case in the moderate restoration option when using an 8% discount rate in conjunction with the realistic and pessimistic scenarios. Neither was it the case when using a 12% discount rate, irrespective of the scenario. Under no scenario was the cost of a comprehensive restoration option outweighed by the benefits quantified, irrespective of the discount rate used. It was concluded that further restoration, in addition to the mere clearing of alien invasive plants, would be economically viable under certain assumptions and conditions.