Plant invasions in South Africa: Insights from the 2017 National Status Report on Biological Invasions
van Wilgen, B.W.
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The impacts of biological invasions are increasing and are felt by all sectors of society. The Department of Environmental Affairs currently invests over R1.5 billion a year on managing biological invasions, mostly on alien plant control. In this talk we discuss the key findings of the first National Status Report on Biological Invasions in South Africa (produced October 2017). In contrast to many other countries, the most diverse, widespread, and damaging invaders in South Africa are plants. They are the third-largest threat to South Africa’s terrestrial biodiversity; invasive trees and shrubs reduce surface water resources by between 3 and 5%; and they have reduced the capacity of natural rangelands to support livestock production by over 100 000 large livestock units. The size of the problem is increasing. While the risk from legally introduced alien species is being addressed, the risk due to accidental introductions is probably increasing. Data from the Southern African Plant Invaders Atlas (SAPIA) show that over the past decade, an average of ten plant species per year have naturalised, and even the most widespread invaders are still spreading. In short, South Africa has a major plant invasion debt. More taxa should be listed under national regulations, but ultimately more needs to be done to ensure that management is strategic and effective. One of the main success stories, however, is biological control. The technology has led to significant and on-going economic returns. If we are to improve policy and management decisions we need more systematic estimates of the area and abundance of plant invasions; more studies documenting the ecological and socio-economic impacts of plant invasions; better planning, including the setting of goals; and better monitoring of the effectiveness of current control operations. We welcome ideas, in particular for how SAPIA should develop in future.