The net economic benefits from eradication of invasive alien vegetation: The case of the Inkomati Catchment Mpumalanga Province in South Africa

Abstract

Invasive alien plants (IAPS) in South Africa threaten the functioning of natural ecosystems. In 1995, the national government established a programme called Working for Water Programme (WFW) aimed at eradicating invasive alien plants and their impacts on the economy and society at large. Investment decisions regarding the programme are predominantly based on the societal costs and benefits emanating from the programme, as well as the rate of returns from every R1 invested into the programme. In order to promote sustainable investment and also to curtail widespread invasion by IAPS in the country, it is essential to close the knowledge gap about these costs and to support research aimed at ascertaining the true monetary values of all the benefits. The specific objectives of the study included applying improved methods and data analysis to measure and value the impacts of IAPS on non-water ecosystem services, particularly carbon sequestration and timber values. The costing structure was also adjusted to account for the opportunity cost of invested capital funds and to consider the social benefit derived from employment opportunities created through the programme. The study employed several models and quantitative methods to assess costs and benefits associated with eradicating IAPS. The Le Maitre et al. (1996) hydrological model was employed to estimate water benefits (savings) from IAPS removal. The study employed direct and indirect market and non-market valuation methods to assign values to the biophysical impacts of IAPS and their removal on the considered ecosystem services. IAPS clearing cost structures have been adjusted to separate capital investment costs and expenditure on labour wages from other components. The estimated values of costs and benefits of IAPS removal were then used to evaluate the net social and economic worth of the WFW programme investments. Results of the study indicate that investing in the eradication of alien vegetation in the study area is economically and socially viable, with benefits due to water savings steadily growing, over time, to constitute 100% of total project benefits after completion of eradication activities. Overall, the IAPS eradication project in the study area generates positive Net Present Value (NPV) and greater than one BCR under all tested project funding scenarios. These results suggest that the WFW programme represents a socially worthwhile investment of the country’s resources.