Chapter 23
Biological Invasions and Ecological
Restoration in South Africa
Patricia M. Holmes , Karen J. Esler , Mirijam Gaertner ,
Sjirk Geerts , Stuart A. Hall , Mlungele M. Nsikani ,
David M. Richardson , and Sheunesu Ruwanza
Abstract Invasive alien plant species can be a major cause of ecosystem degradation in South Africa, and ecosystem recovery may require restoration interventions
beyond controlling the target alien species. Active restoration interventions are
usually required if legacy effects result from the invasion. Legacy effects may induce
regime shifts when thresholds to autogenic recovery are breached. In such cases,
active restoration interventions will be required to manipulate the ecosystem along a
trajectory to recovery. In some cases, alien control measures may be sufficient to
restore a structurally and functionally representative ecosystem, provided that implementation occurs early in the invasion process and that the control methods do not
hamper spontaneous regeneration. It is important that key stakeholders discuss and
set realistic restoration goals at the project planning stage. Studies on the costs and
benefits of ecological restoration indicate that when important services are improved,
benefits outweigh the costs of alien clearing (assuming spontaneous regeneration of
the native ecosystem). The costs of moderate, active restoration interventions are
P. M. Holmes (*) · K. J. Esler · S. A. Hall
Centre for Invasion Biology, Department of Conservation Ecology and Entomology,
Stellenbosch University, Stellenbosch, South Africa
e-mail: holmes.patricia.m@gmail.com
M. Gaertner
Nürtingen-Geislingen University of Applied Sciences, Nürtingen, Germany
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
S. Geerts
Centre for Invasion Biology, Department of Conservation and Marine Sciences, Cape Peninsula
University of Technology, Cape Town, South Africa
M. M. Nsikani · D. M. Richardson
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
S. Ruwanza
Centre for Invasion Biology, Department of Environmental Science, Rhodes University,
Makhanda, South Africa
© The Author(s) 2020
B. W. van Wilgen et al. (eds.), Biological Invasions in South Africa, Invading
Nature - Springer Series in Invasion Ecology 14,
https://doi.org/10.1007/978-3-030-32394-3_23
665
Biological Invasions and Ecological
Restoration in South Africa
Patricia M. Holmes , Karen J. Esler , Mirijam Gaertner ,
Sjirk Geerts , Stuart A. Hall , Mlungele M. Nsikani ,
David M. Richardson , and Sheunesu Ruwanza
Abstract Invasive alien plant species can be a major cause of ecosystem degradation in South Africa, and ecosystem recovery may require restoration interventions
beyond controlling the target alien species. Active restoration interventions are
usually required if legacy effects result from the invasion. Legacy effects may induce
regime shifts when thresholds to autogenic recovery are breached. In such cases,
active restoration interventions will be required to manipulate the ecosystem along a
trajectory to recovery. In some cases, alien control measures may be sufficient to
restore a structurally and functionally representative ecosystem, provided that implementation occurs early in the invasion process and that the control methods do not
hamper spontaneous regeneration. It is important that key stakeholders discuss and
set realistic restoration goals at the project planning stage. Studies on the costs and
benefits of ecological restoration indicate that when important services are improved,
benefits outweigh the costs of alien clearing (assuming spontaneous regeneration of
the native ecosystem). The costs of moderate, active restoration interventions are
P. M. Holmes (*) · K. J. Esler · S. A. Hall
Centre for Invasion Biology, Department of Conservation Ecology and Entomology,
Stellenbosch University, Stellenbosch, South Africa
e-mail: holmes.patricia.m@gmail.com
M. Gaertner
Nürtingen-Geislingen University of Applied Sciences, Nürtingen, Germany
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
S. Geerts
Centre for Invasion Biology, Department of Conservation and Marine Sciences, Cape Peninsula
University of Technology, Cape Town, South Africa
M. M. Nsikani · D. M. Richardson
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
S. Ruwanza
Centre for Invasion Biology, Department of Environmental Science, Rhodes University,
Makhanda, South Africa
© The Author(s) 2020
B. W. van Wilgen et al. (eds.), Biological Invasions in South Africa, Invading
Nature - Springer Series in Invasion Ecology 14,
https://doi.org/10.1007/978-3-030-32394-3_23
665