Chapter 21
The Extent and Effectiveness of Alien Plant
Control Projects in South Africa
Brian W. van Wilgen , John R. Wilson , Andrew Wannenburgh ,
and Llewellyn C. Foxcroft
Abstract Since 1995, the South African government has spent at least ZAR
15 billion (unadjusted for inflation; approximately USD1 billion) on alien plant
control operations across South Africa. The amount spent per year has risen
exponentially since 2010, and in 2019 annual spending is around ZAR 2 billion
per year. Based on a small (but growing) number of case studies that have
assessed management effectiveness, it is clear that the cover of invasive alien
plants has been reduced in some localised areas, but continues to grow in
others. A number of factors contribute to success, but the effort and resources
required for successful control appear to be routinely under-estimated, with
actual costs between 1.5 and 8.6 times higher than initial budget estimates.
Currently, therefore, control measures (other than biological control) have
largely failed to check invasions at a national scale, and there have been no
documented eradications of plant invasions from continental South Africa. We
argue that control can be considerably improved by effective prioritisation,
goal-setting and planning; monitoring of outcomes rather than of inputs;
B. W. van Wilgen (*)
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
e-mail: bvanwilgen@sun.ac.za
J. R. Wilson
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
South African National Biodiversity Institute, Kirstenbosch Research Centre, Cape Town,
South Africa
A. Wannenburgh
Department of Environment, Forestry and Fisheries, Cape Town, South Africa
L. C. Foxcroft
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
Conservation Services, South African National Parks, Skukuza, 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_21
597
The Extent and Effectiveness of Alien Plant
Control Projects in South Africa
Brian W. van Wilgen , John R. Wilson , Andrew Wannenburgh ,
and Llewellyn C. Foxcroft
Abstract Since 1995, the South African government has spent at least ZAR
15 billion (unadjusted for inflation; approximately USD1 billion) on alien plant
control operations across South Africa. The amount spent per year has risen
exponentially since 2010, and in 2019 annual spending is around ZAR 2 billion
per year. Based on a small (but growing) number of case studies that have
assessed management effectiveness, it is clear that the cover of invasive alien
plants has been reduced in some localised areas, but continues to grow in
others. A number of factors contribute to success, but the effort and resources
required for successful control appear to be routinely under-estimated, with
actual costs between 1.5 and 8.6 times higher than initial budget estimates.
Currently, therefore, control measures (other than biological control) have
largely failed to check invasions at a national scale, and there have been no
documented eradications of plant invasions from continental South Africa. We
argue that control can be considerably improved by effective prioritisation,
goal-setting and planning; monitoring of outcomes rather than of inputs;
B. W. van Wilgen (*)
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
e-mail: bvanwilgen@sun.ac.za
J. R. Wilson
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
South African National Biodiversity Institute, Kirstenbosch Research Centre, Cape Town,
South Africa
A. Wannenburgh
Department of Environment, Forestry and Fisheries, Cape Town, South Africa
L. C. Foxcroft
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
Conservation Services, South African National Parks, Skukuza, 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_21
597