The cost of water hyacinth control in South Africa: a case study of three options
AbstractThe aquatic plant water hyacinth (Eichhornia crassipes) was first recorded in South Africa during the early part of the 20th century. The plant has since spread across the country and is found in water bodies in both sub-tropical and temperate areas. The biology, ecology and impacts of water hyacinth are well studied, but sound and cost-effective management of it remains an enormous challenge in South Africa. Since the 1970s, control programmes have focused on the use of herbicides, with some success, while biological and integrated control have historically received less effort and investment, despite the successes of the latter control approaches in other parts of Africa and elsewhere in the world. The reasons for the relative successes and challenges associated with the various control approaches vary substantially. Herbicidal control has been an effective short-term solution with highly visible results. However, the cases used in this study show that herbicidal control is approximately five times (R1 481/ha) less cost-effective than either biological or integrated control, mainly because it requires resource-intensive follow-up procedures.
The effectiveness of large-scale herbicidal control has mainly been influenced by inappropriate field application, plus management and institutional inconsistencies. Biological control offers a longer term, cheaper (R309/ha and potentially R3.60/ha) and less resource-intensive solution compared to herbicidal treatment, but the effectiveness of this approach relies heavily on the successful release of control agents, the ability of biocontrol agents to thrive under a range of climatic conditions and the extent to which affected water bodies are nutrient-enriched. Based on the analysis here, integrated control was the most cost-effective control option at an average cost of R277/ha. This approach enables managers to integrate selected aspects of herbicidal and biological control and it is also more likely to facilitate the development of partnerships in water hyacinth control programs. Discussion of a possible `no control' option suggests that the economic and environmental costs of no control may be far greater than any control.
Recommendations include: the selection of appropriate management option/s should be based on management needs across different time scales and on objective cost-benefit information this will help to determine how the costs and benefits of different control approaches could be distributed amongst those who pay for and benefit from the management of water hyacinth. Successful management will also rely on selecting appropriate and sound ecological approaches suited to local conditions; management will also need to facilitate the integration of control efforts at the catchment level as well as institutional and partnership integration to ensure continuity in the ownership of water hyacinth control.
Keywords: aquatic weeds; Eichhornia crassipes; herbicides; biological control; integrated control; management costs; management benefits; catchment management
(Afr J Aqua Sci: 2002 27(2): 141-149)