2.8 Research on Alien Plant Invasions at the CSIR (1990–
Present)
Researchers at the Jonkershoek Forestry Research Centre continued their work on
invasive alien species after the transfer of the Centre to the CSIR. By 1994, research
led by Brian van Wilgen and David Le Maitre (and based on afforestation experiments at Jonkershoek) estimated that, if unchecked, alien plant invasions would
potentially reduce water supplies to the city of Cape Town by 30% (Le Maitre et al.
1996). It was also estimated that more water could be delivered, at a lower unit cost,
through the integration of alien plant control and the maintenance of water supply
infrastructure (van Wilgen et al. 1996). This information was presented to Kader
Asmal (the Minister of Water Affairs and Forestry) on 2 June 1995, and this in turn
provided the rationale for the establishment of WfW (van Wilgen and Wannenburgh
2016).
Because invasive alien plant control is an expensive undertaking, it became
important to investigate whether or not spending on control would deliver sufficient
returns on investment. The CSIR team addressed these issues and conducted several
pioneering economic studies. These studies demonstrated (1) that alien plant control
could be effective and efficient, as the cost of water would be lower if delivered from
catchments where alien plant control was in place, compared to catchments where no
control was in place (van Wilgen et al. 1997); (2) that the highest returns on
investment would be realised if mechanical and biological control of Acacia
mearnsii (Black Wattle) was carried out in parallel with commercial growing
activities (De Wit et al. 2001); and (3) that spending on biological control had
delivered extremely attractive returns on investment in the case of several invasive
plant species in South Africa (van Wilgen et al. 2004). Moran et al. (2013) noted that
“[biological control] research efforts in South Africa have enjoyed increasing
political and public credibility, at least in part because of the involvement of
personnel from the South African Council for Scientific and Industrial Research
who have shown that [biological control] is highly cost-effective and that it constitutes an essential supplement to other management practices”.
Work at the CSIR also sought to expand the understanding of the effects of
invasive alien plants beyond their impacts on water at local scales. A team, including
Brian van Wilgen, David Le Maitre, Belinda Reyers, Willem De Lange, Mark Gush
and Sebinasi Dzikiti used plant distribution data, simulation models, and economic
principles to scale up local studies to a national scale. They showed that (1) invasive
alien plants would have serious consequences for water resources, rangeland productivity, and biodiversity on all of South Africa’s terrestrial biomes, if left to spread
in an uncontrolled manner (van Wilgen et al. 2008); (2) that the value of ecosystem
services currently being lost to invasive alien plants amounted to ZAR6.5 billion
annually, and would continue to grow unless the invasions were contained
(De Lange and van Wilgen 2010); and (3) that the combined impacts of invasive
alien plants on surface water runoff in South Africa were between 1444 to 2444
million m
3 per year, but that if no remedial action is taken, reductions in water
resources could rise to between 2589 and 3153 million m
3 per year, about 50%
48
B. W. van Wilgen
Present)
Researchers at the Jonkershoek Forestry Research Centre continued their work on
invasive alien species after the transfer of the Centre to the CSIR. By 1994, research
led by Brian van Wilgen and David Le Maitre (and based on afforestation experiments at Jonkershoek) estimated that, if unchecked, alien plant invasions would
potentially reduce water supplies to the city of Cape Town by 30% (Le Maitre et al.
1996). It was also estimated that more water could be delivered, at a lower unit cost,
through the integration of alien plant control and the maintenance of water supply
infrastructure (van Wilgen et al. 1996). This information was presented to Kader
Asmal (the Minister of Water Affairs and Forestry) on 2 June 1995, and this in turn
provided the rationale for the establishment of WfW (van Wilgen and Wannenburgh
2016).
Because invasive alien plant control is an expensive undertaking, it became
important to investigate whether or not spending on control would deliver sufficient
returns on investment. The CSIR team addressed these issues and conducted several
pioneering economic studies. These studies demonstrated (1) that alien plant control
could be effective and efficient, as the cost of water would be lower if delivered from
catchments where alien plant control was in place, compared to catchments where no
control was in place (van Wilgen et al. 1997); (2) that the highest returns on
investment would be realised if mechanical and biological control of Acacia
mearnsii (Black Wattle) was carried out in parallel with commercial growing
activities (De Wit et al. 2001); and (3) that spending on biological control had
delivered extremely attractive returns on investment in the case of several invasive
plant species in South Africa (van Wilgen et al. 2004). Moran et al. (2013) noted that
“[biological control] research efforts in South Africa have enjoyed increasing
political and public credibility, at least in part because of the involvement of
personnel from the South African Council for Scientific and Industrial Research
who have shown that [biological control] is highly cost-effective and that it constitutes an essential supplement to other management practices”.
Work at the CSIR also sought to expand the understanding of the effects of
invasive alien plants beyond their impacts on water at local scales. A team, including
Brian van Wilgen, David Le Maitre, Belinda Reyers, Willem De Lange, Mark Gush
and Sebinasi Dzikiti used plant distribution data, simulation models, and economic
principles to scale up local studies to a national scale. They showed that (1) invasive
alien plants would have serious consequences for water resources, rangeland productivity, and biodiversity on all of South Africa’s terrestrial biomes, if left to spread
in an uncontrolled manner (van Wilgen et al. 2008); (2) that the value of ecosystem
services currently being lost to invasive alien plants amounted to ZAR6.5 billion
annually, and would continue to grow unless the invasions were contained
(De Lange and van Wilgen 2010); and (3) that the combined impacts of invasive
alien plants on surface water runoff in South Africa were between 1444 to 2444
million m
3 per year, but that if no remedial action is taken, reductions in water
resources could rise to between 2589 and 3153 million m
3 per year, about 50%
48
B. W. van Wilgen