The Management of Invasive Alien Plants in South Africa: Strategy, Progress and Challenges

Almost 900 species of alien plants have escaped cultivation and established populations in the wild in South Africa. About two thirds of these established alien species have become invasive, spreading into natural ecosystems. Many of them still have relatively restricted distributions in South Africa, but a growing number are becoming alarmingly widespread. These widespread species include many alien trees, such as pines (Pinus species), wattles (Acacia species) and mesquite (Prosopis species), as well as a host of shrubby, herbaceous and succulent species. In South Africa, alien plants are estimated to cover almost 7% of the country, and many species are now entering a phase of exponential growth. This problem has been recognised for over a century in South Africa, mainly because of the negative impact that alien plants have had on rangelands utilised for livestock production. However, it was the realization that alien plants, and especially alien trees, were responsible for the reduction of stream-flow from water catchment areas that triggered a large expansion in control efforts in 1995. This article provides a brief description of the policies and strategies adopted in South Africa to address this problem, reviews the progress that has been made with control efforts, and outlines the main challenges that face the managers of alien plant control projects. South Africa has adopted a diversified approach to the control of invasive alien plants. The approach is supported by legislation, and government funding is provided to address a range of aspects. Ultimately, the goal of these interventions is to reach a "maintenance level" for as many species in as many localities as possible (although this goal is seldom explicitly stated). The concept of a maintenance level recognises that, for many invasions, eradication is infeasible, but that the problem can be reduced to a level where the negative impacts are negligible and control costs are relatively low in perpetuity. The most important features of South Africa?s approach to invasive alien plant management are outlined in the article. The outcome has been South Africa has been fortunate in that there is a high level of awareness around the issue of biological invasions, and this has resulted in a remarkable level of funding for an environmental issue in a developing country that has to meet substantial demands on funding for other priorities. This challenge has been partly overcome by linking alien plant control projects to employment creation. There have been some important successes (notably with biological control), but currently the funding is insufficient to address all problems everywhere. The existence of dual goals (ecological restoration and the creation of employment) is a double-edged sword. On the one hand, it is absolutely essential for the retention of the political support that ensures funding, but on the other it restricts the ability to focus funds where they are most needed for ecosystem restoration purposes. The biggest challenge in the future will be finding politically acceptable ways of focussing control efforts so that their efficiency can be maximised at a national scale. To fail to do this will simply see the problem run away from us, with dire consequences for the delivery of vital ecosystem services to future generations.