There is an urgent need for an accurate alien flora for South Africa, both to ensure
that current invasions are properly managed, and that the risk of future invasions can
be identified and minimised (see Sect. 3.3.1, and Kumschick et al. 2020, Chap. 20,
for more details). The alien flora should include objective information on the
introduction status of each taxon according to the unified framework for biological
invasions (Blackburn et al. 2011; Wilson et al. 2018). It should be updated regularly
as part of the processes for completion of the triennial national status reports
mandated in legislation (van Wilgen and Wilson 2018).
“Alien plant species assemblage zones” (Fig. 3.4) reflect the outcome of decades
of alien plant taxa arranging themselves in space following human-mediated introduction and dissemination and interactions with environmental (Wilson et al. 2020,
Chap 13) and biotic (Le Roux et al. 2020, Chap 14) features of South African
ecosystems. The dimensions and determinants of these species assemblages and the
zones they occupy deserve further attention; these zones potentially define ecologically meaningful spatial units for national-scale planning (Fig. 3.4).
There is also a need for a systematic monitoring system to detect and track
invasions (Latombe et al. 2017). This should incorporate active on-ground surveillance, remote sensing, and citizen science initiatives [e.g. expanding SAPIA to tap
into iNaturalist (https://www.inaturalist.org/), and drone and satellite technology].
Visser et al. (2014) showed the value of freely available Google Earth imagery for
detecting changes in the distribution of invasive alien plants, especially trees. A
series of sentinel sites could be established to allow for the monitoring of the extent
of invasions of key taxa and sites.
The dimensions of the invasion debt in South Africa’s alien flora requires much
more research. Many naturalised species are clearly poised to invade large areas; the
potential ranges of these species need to be determined to inform response efforts.
Acknowledgements Much of the work reviewed in this chapter was supported by the DSI-NRF
Centre of Excellence for Invasion Biology. We salute Lesley Henderson for her dedication to the
collation of distribution data that now forms the Southern African Plant Invader Atlas (SAPIA) and
thank her for responses to many questions during the preparation of the chapter. Many other
colleagues also provided insights on many topics. The South African Department of Environment,
Forestry, and Fisheries (DEFF) are thanked for funding the South African National Biodiversity
Institute noting that this publication does not necessarily represent the views or opinions of DEFF or
its employees.
Electronic Supplementary Material
The online version of this chapter contains supplementary material, which is available to authorised users: Supplementary Appendix 3.1 (https://doi.org/10.5281/
zenodo.3562046); Supplementary Appendices 3.2–3.4 (https://doi.org/10.5281/
zenodo.3660871).
3 The Biogeography of South African Terrestrial Plant Invasions
89
that current invasions are properly managed, and that the risk of future invasions can
be identified and minimised (see Sect. 3.3.1, and Kumschick et al. 2020, Chap. 20,
for more details). The alien flora should include objective information on the
introduction status of each taxon according to the unified framework for biological
invasions (Blackburn et al. 2011; Wilson et al. 2018). It should be updated regularly
as part of the processes for completion of the triennial national status reports
mandated in legislation (van Wilgen and Wilson 2018).
“Alien plant species assemblage zones” (Fig. 3.4) reflect the outcome of decades
of alien plant taxa arranging themselves in space following human-mediated introduction and dissemination and interactions with environmental (Wilson et al. 2020,
Chap 13) and biotic (Le Roux et al. 2020, Chap 14) features of South African
ecosystems. The dimensions and determinants of these species assemblages and the
zones they occupy deserve further attention; these zones potentially define ecologically meaningful spatial units for national-scale planning (Fig. 3.4).
There is also a need for a systematic monitoring system to detect and track
invasions (Latombe et al. 2017). This should incorporate active on-ground surveillance, remote sensing, and citizen science initiatives [e.g. expanding SAPIA to tap
into iNaturalist (https://www.inaturalist.org/), and drone and satellite technology].
Visser et al. (2014) showed the value of freely available Google Earth imagery for
detecting changes in the distribution of invasive alien plants, especially trees. A
series of sentinel sites could be established to allow for the monitoring of the extent
of invasions of key taxa and sites.
The dimensions of the invasion debt in South Africa’s alien flora requires much
more research. Many naturalised species are clearly poised to invade large areas; the
potential ranges of these species need to be determined to inform response efforts.
Acknowledgements Much of the work reviewed in this chapter was supported by the DSI-NRF
Centre of Excellence for Invasion Biology. We salute Lesley Henderson for her dedication to the
collation of distribution data that now forms the Southern African Plant Invader Atlas (SAPIA) and
thank her for responses to many questions during the preparation of the chapter. Many other
colleagues also provided insights on many topics. The South African Department of Environment,
Forestry, and Fisheries (DEFF) are thanked for funding the South African National Biodiversity
Institute noting that this publication does not necessarily represent the views or opinions of DEFF or
its employees.
Electronic Supplementary Material
The online version of this chapter contains supplementary material, which is available to authorised users: Supplementary Appendix 3.1 (https://doi.org/10.5281/
zenodo.3562046); Supplementary Appendices 3.2–3.4 (https://doi.org/10.5281/
zenodo.3660871).
3 The Biogeography of South African Terrestrial Plant Invasions
89