expertise within many organs of state (van Wilgen and Wilson 2018). Furthermore,
while most protected areas have prepared management plans as required by NEM:
PAA, the sections of these plans that deal with alien plant control are typically highlevel, long-term statements of intent, and these have not been effectively carried
forward into the more detailed medium to short-term plans that would be necessary
for guiding control operations (van Wilgen et al. 2017).
Creating accurate maps of the distribution and abundance of alien plant invasions
as a basis for realistic planning has also proved challenging up to now (Richardson
et al. 2020, Chap. 3). At a national scale, there have been at least three attempts to
map the extent of the problem. In 1993, the Council for Scientific and Industrial
Research mapped invasive alien plants in South Africa, with the goal of estimating
their impact at a national scale (Le Maitre et al. 2000). The mapping techniques used
were coarse due to the paucity of reliable data, but a map at a 1:250,000 scale was
produced, based primarily on the local knowledge of natural resource experts from
across South Africa. The project estimated that invasive plants occupied 10.1 million
ha (6.82% of South Africa and Lesotho). The longest-running project aimed at
recording information on the national extent of alien plants is the Southern African
Plant Invaders Atlas (SAPIA), which was initiated in 1994 (Henderson 2007). As
of May 2016, SAPIA had over 87,000 geo-referenced records for 773 alien plant
taxa that are present outside of cultivation in southern Africa, making it the most
extensive source of information on the distribution of invasive plants in the region
(see Richardson et al. 2020). In 2008, the Department of Environmental Affairs
commissioned the Agricultural Research Council to develop and implement a repeatable sampling protocol to track trends in alien plant distribution and density across
half of the country. This project has run for more than a decade, and has mapped the
distribution of 27 alien plant taxa (species in the genera Pinus, Eucalyptus and some
Australian Acacia species were mapped collectively). The project is ongoing, but no
adequate description of the sampling methodology has been published to date, nor
have any peer-reviewed papers that present the findings been published.
At finer scales, relatively detailed maps of the extent of invasion have been
developed for some areas, mostly protected areas [e.g. Foxcroft et al. (2004, 2009)
for Kruger National Park; Cheney et al. (2018) for Table Mountain National Park; and
van Wilgen et al. (2016) for protected areas in the Cape Floristic region]. Cheney et al.
(2018) compiled a map of invasive alien plants derived from fine-scale systematic
sampling of the entire Table Mountain National Park (26,500 ha), and compared this
to two other datasets in use for planning and management. They found that management datasets overestimated species cover by orders of magnitude, and that this
resulted in questionable allocations of funding. They concluded that “contrary to
perception, fine-scale surveys are a cost-effective way to inform long-term monitoring
programmes and improve programme effectiveness”. In addition, where plans are
developed, they are not always followed (Kraaij et al. 2017). It appears, thus, that the
level of planning for alien plant control in South Africa falls substantially short both of
what is required by law and what is necessary for management to be effective.
610
B. W. van Wilgen et al.
while most protected areas have prepared management plans as required by NEM:
PAA, the sections of these plans that deal with alien plant control are typically highlevel, long-term statements of intent, and these have not been effectively carried
forward into the more detailed medium to short-term plans that would be necessary
for guiding control operations (van Wilgen et al. 2017).
Creating accurate maps of the distribution and abundance of alien plant invasions
as a basis for realistic planning has also proved challenging up to now (Richardson
et al. 2020, Chap. 3). At a national scale, there have been at least three attempts to
map the extent of the problem. In 1993, the Council for Scientific and Industrial
Research mapped invasive alien plants in South Africa, with the goal of estimating
their impact at a national scale (Le Maitre et al. 2000). The mapping techniques used
were coarse due to the paucity of reliable data, but a map at a 1:250,000 scale was
produced, based primarily on the local knowledge of natural resource experts from
across South Africa. The project estimated that invasive plants occupied 10.1 million
ha (6.82% of South Africa and Lesotho). The longest-running project aimed at
recording information on the national extent of alien plants is the Southern African
Plant Invaders Atlas (SAPIA), which was initiated in 1994 (Henderson 2007). As
of May 2016, SAPIA had over 87,000 geo-referenced records for 773 alien plant
taxa that are present outside of cultivation in southern Africa, making it the most
extensive source of information on the distribution of invasive plants in the region
(see Richardson et al. 2020). In 2008, the Department of Environmental Affairs
commissioned the Agricultural Research Council to develop and implement a repeatable sampling protocol to track trends in alien plant distribution and density across
half of the country. This project has run for more than a decade, and has mapped the
distribution of 27 alien plant taxa (species in the genera Pinus, Eucalyptus and some
Australian Acacia species were mapped collectively). The project is ongoing, but no
adequate description of the sampling methodology has been published to date, nor
have any peer-reviewed papers that present the findings been published.
At finer scales, relatively detailed maps of the extent of invasion have been
developed for some areas, mostly protected areas [e.g. Foxcroft et al. (2004, 2009)
for Kruger National Park; Cheney et al. (2018) for Table Mountain National Park; and
van Wilgen et al. (2016) for protected areas in the Cape Floristic region]. Cheney et al.
(2018) compiled a map of invasive alien plants derived from fine-scale systematic
sampling of the entire Table Mountain National Park (26,500 ha), and compared this
to two other datasets in use for planning and management. They found that management datasets overestimated species cover by orders of magnitude, and that this
resulted in questionable allocations of funding. They concluded that “contrary to
perception, fine-scale surveys are a cost-effective way to inform long-term monitoring
programmes and improve programme effectiveness”. In addition, where plans are
developed, they are not always followed (Kraaij et al. 2017). It appears, thus, that the
level of planning for alien plant control in South Africa falls substantially short both of
what is required by law and what is necessary for management to be effective.
610
B. W. van Wilgen et al.