Biological Invasions and Ecological Restoration in South Africa

Abstract

Invasive alien plant species can be a major cause of ecosystem degrada- 7 AU2 tion in South Africa, and ecosystem recovery may require restoration interventions 8 beyond controlling the target alien species. Active restoration interventions are 9 usually required if legacy effects result from the invasion. Legacy effects may induce 10 regime shifts when thresholds to autogenic recovery are breached. In such cases, 11 active restoration interventions will be required to manipulate the ecosystem along a 12 trajectory to recovery. In some cases, alien control measures may be sufficient to 13 restore a structurally and functionally representative ecosystem, provided that imple- 14 mentation occurs early in the invasion process and that the control methods do not 15 hamper spontaneous regeneration. It is important that key stakeholders discuss and 16 set realistic restoration goals at the project planning stage. Studies on the costs and 17 benefits of ecological restoration indicate that when important services are improved, 18 benefits outweigh the costs of alien clearing (assuming spontaneous regeneration of 19 the native ecosystem). The costs of moderate, active restoration interventions areeconomically viable, whereas the costs of fully restoring ecosystem structure, 22 functioning and composition in highly degraded ecosystems are rarely deemed 23 economically justifiable. Valuations of specific biodiversity components, such as 24 threatened ecosystems and species, remain problematic to assess, and these compo- 25 nents could be under-valued in such studies. South African researchers have made 26 significant contributions to the theory and practice of restoration ecology globally 27 and have produced local guidelines for ecological restoration. However, there has 28 been limited uptake in implementing active restoration projects at larger scales. This 29 apparent knowing-doing gap may have three causes: firstly, insufficient 30 co-production by all stakeholders in planning restoration projects, including 31 prioritisation and goal setting; secondly, shifting beyond clearing invasive alien 32 species to restoring ecosystems; and thirdly, insufficient resources to implement 33 active restoration projects at the necessary scale. To achieve Convention on Biolog- 34 ical Diversity and the UN Sustainable Development Goals, interventions must shift 35 from controlling invasive alien species alone to restoring native ecosystem structure 36 and functioning.