Potential Futures of Biological Invasions in South Africa

Open Access
Part of the Invading Nature - Springer Series in Invasion Ecology book series (INNA, volume 14)


Biological invasions are having a moderately negative impact on human livelihoods and the environment in South Africa, but the situation is worsening. Predicting future trends is fraught with many assumptions, so this chapter takes an outcome-orientated approach. We start by envisaging four scenarios for how biological invasions might look like 200–2000 years from now: (1) “Collapse of Civilisation, but no return to Eden”, there is no advanced human civilisation left on Earth and current biological invasions play out in full; (2) “New Pangea”, a combination of the unregulated and rapid movement of species around the world and other global change drivers leads to the biotic homogenisation of areas that were previously distinct biogeographic regions such that the concept of biological invasions no longer has meaning; (3) “Preserve or Use”, while parts of the Earth continue to be utilised, some areas are actively managed and native biodiversity and biogeographic distributions are maintained; and (4) “Conservation Earth”, a highly advanced civilisation restores the Earth to a state prior to the human-mediated movement of organisms (i.e. biological invasions are reversed).

Based on various horizon-scanning exercises and our own deliberations, we discuss how technological, socio-political, trade, global change, and ecological-evolutionary processes in South Africa might affect biological invasions by 2070 (i.e. when people born today will be the key decision-makers). Finally, we explore how planning, regulation, funding, public support, and research might affect invasions by 2025 (i.e. over the next planning/management/political cycle). There are many things we can neither predict nor influence, but, in part based on the insights from this book, we highlight some actions that could enable the next generation to decide what they want their future to be. A greater focus on appropriate and innovative training opportunities would increase the efficacy and responsiveness of the management of biological invasions. A shift in regulatory approach from “identify and direct” to a variety of flexible, inclusive, and sophisticated approaches underpinned by evidence might provide more societally acceptable means of addressing the multitude of competing interests. Greater co-operation on biosecurity and implementation with neighbouring countries would assist prevention measures. Finally, monitoring and research aimed at documenting, tracking, and predicting invasions and their impacts would assist with efforts to identify priorities and help us to understand the consequence of different management and policy decisions. While this was a sobering exercise, it was also empowering. If South Africans can agree on a long-term trajectory for how they want to deal with biological invasions, the potential consequences of decision-making over the short-term will become much clearer.

31.1 Introduction

This book on biological invasions in South Africa has focussed on the current state of invasions in South Africa and the processes that have led us to this point. It has highlighted the fascinating interplay between socio-economic factors and biological processes that have determined which alien species have been introduced, where they have spread to, what impacts have occurred, and how South African society has responded. This is largely because the book set out to be encyclopaedic (van Wilgen et al. 2020a, Chap.  1). However, biological invasions are fundamentally dynamic and are an important component of global change (van Wilgen et al. 2020b, Chap.  29). It would therefore be remiss not to conclude with an evaluation of what the future might bring. This chapter examines possible scenarios for biological invasions globally and in South Africa, and aims to show how different events and decisions could set us on radically different trajectories.

There has been an increasing wave of interest in conducting horizon-scanning, both for conservation generally and for invasion science specifically, with the aim of anticipating and preparing for problems (Ricciardi et al. 2017; Sutherland and Woodroof 2009). However, such exercises typically only consider what could happen over the next few planning cycles. This chapter takes a different approach. Although we rely heavily on existing projections, we focus first on the long-term (i.e. on what the “end-points” might be), and work back through time. Our approach was inspired by a recent exercise that considered potential futures for human civilisation and identified four basic trajectories: civilisation could conquer space; technological transformations could be such that what we now recognise as ‘human’ would no longer be relevant; civilisation could continue to develop, but with no transformative changes (status quo); or there could be a catastrophic end (Baum et al. 2019). These trajectories form the basis for evaluating the consequences of actions taken now. Thinking in this way balances short-termism that permeates most planning and political cycles and pitches thinking back into ‘Long Now’ time scales consistent with the functioning of ecosystems (Brand 2008). On this basis, and noting that the focus is on biological invasions rather than other global change drivers, we consider invasions over three time-periods:
  • The long-term: the transfer of species across biogeographical barriers by humans in South Africa started slowly probably around 2000 years before present and has accelerated particularly over the last 200 years (Deacon 1986; Faulkner et al. 2020, Chap.  12). What will the situation look like in South Africa 200–2000 years from now? We assume that there will have been no significant shifts in tectonic plates (although there might be significant tectonic activity, important shifts in ocean currents, and sea-level changes), and assume that substantially new and diverse phylogenetic lineages will not yet have evolved.

  • 2070: the need for inter-generational thinking is a principle embedded within conservation science; the choice of a 50-year time horizon is meant to reflect this. Specifically, what will South Africa look like when children born today become the decision makers? (although the age profile of decision-makers might and maybe should shift).

  • 2025: current decisions are, of course, still made in the context of policy and management planning horizons, usually covering no more than the next 5 years (e.g. elections or government funding cycles).

For the 2070 and 2025 time periods we consider how different events and drivers are likely to put us on a trajectory to one of the long-term scenarios.

31.2 The Long-Term: What Will Invasions Look Like 200–2000 Years from Now?

Below we sketch out four long-term scenarios (Table 31.1). The inspiration for these came largely from the scenarios of Baum et al. (2019) and post-lunch discussions at the wine farm Lovane (close to Stellenbosch). However, they undoubtedly also arose from nascent ideas buried deep in our memories of concepts more eloquently expressed by other authors.
Table 31.1

The possible causes, outcomes, and consequences for South Africa of four long-term scenarios for biological invasions (i.e. 200–2000 years from now)


Possible causes


Examples from South Africa

(with a focus on the Fynbos Biome).

Collapse of civilisation but no return to Eden (Fig. 31.2a)

...nuclear war, collision between Earth and a large asteroid or comet, super-volcano eruption, global warming, runaway artificial intelligence, physics experiment disasters, major disease outbreaks, and scenarios involving multiple major catastrophes” (Baum et al. 2019).

Substantial intercontinental human-mediated dispersal of organisms ceases, but the impacts of existing biological invasions play out in full.

Dispersal processes would be akin to the situation before human civilisation (Wilson et al. 2009). Over time, biogeographical breaks would re-establish, and there would be a drift back towards fundamental biogeographical/community ecology principles (if any exist). However, it is likely that that the phylogeographic signal of biological invasions would be long-lasting as many native species would have been driven to extinction by invasive species before they could adapt resulting in the loss of evolutionary lineages (e.g. the replacement of marsupials and monotremes by placental mammals), with a general but transient shift from K-selected to r-selected species.

In South Africa, amongst many other effects, the Fynbos Biome would disappear and be transformed to a mixture of alien shrubs and trees.

Over about a third of the country, where annual rainfall is <350 mm, invasive Prosopis trees would dominate. Such ecosystems would no longer support large mammalian herbivores.

New Pangea (Fig. 31.2b)

Narrow utilitarian concerns dominate decisions due to the need to respond to crises; the valuation of biodiversity changes significantly; or there is a complete break-down in global co-operation in biosecurity.

Biogeographical patterns and dispersal rates are changed to such a degree that the alien/native distinction is no longer meaningful (cf. Wilson et al. 2016). As pathways of introduction and spread are not managed, there will likely be a suite of panmictic organisms that come to dominate the globe.

The globalisation of dispersal has already lead to the homogenisation of many faunas and floras (though the introduction of alien organisms can, in special cases, also lead to differentiation). In this scenario homogenisation would be taken to the extreme. Species distributions would be a function of their climate niches and either their utility for humans or their inherent competitiveness. Biological invasions will have no meaning in this scenario.

Trees and shrubs in the Fynbos Biome might be controlled to preserve water supply, but the Fynbos would likely be transformed by other species (e.g. invasive grasses). The area would become indistinguishable in species from other areas of the world with a similar climate (currently Mediterranean-type ecosystems).

Rangelands will be transformed by a suite of herbaceous, woody and succulent invaders, some (but not all) of which may be palatable. The potential for livestock production will decline.

Preserve or Use (Fig. 31.2c)

There is a pragmatic global agreement to protect some areas based on historical biogeographical patterns, while ensuring that other areas are used sustainably for production.

The Earth is separated into discrete areas that are either: (1) set aside as natural and conserved based on some reference point; (2) are considered areas where key ecosystem processes are maintained without concern over the nativity of the system (e.g. novel ecosystems); or (3) targeted primarily for utilisation.

Active interventions to maintain biogeographical patterns and processes would need to continue in perpetuity, with decisions made as to which areas to preserve as natural (i.e. with the goal of retaining historical biogeographical distributions).

This would likely involve on-going conflicts and trade-offs, noting that once biogeographic distributions have eroded it can be very difficult to reverse them. This might point to the need for fairly authoritarian rules governing protected areas, and global rules governing trade and transport to ensure biosecurity.

Governmental protection would achieve and maintain the goal of ensuring patches of the Fynbos Biome were kept alien-free, but large areas would still be used for urban and agricultural purposes.

South African megafauna are confined to protected areas, which have to be intensively maintained and kept alien free.

Conservation Earth (Fig. 31.2d)

Humankind collectively decides that the Earth should be preserved in toto for posterity.

Substantial intercontinental human-mediated dispersal of organisms ceases, and the impacts of existing biological invasions are curtailed and in many cases reversed.

Biodiversity patterns and processes return to some historical reference point, and from there allowed to carry on in essence without human intervention. Evolution is allowed to continue, and rates of extinction, speciation, and dispersal return to rates that were observed before human interventions. The current mass extinction is brought to an end (cf. the first scenario where the impacts of biological invasions would continue). Human impacts (e.g. through tourism) are kept at negligible levels.

Alien species in the Fynbos Biome would either be entirely removed or managed such that they have negligible impacts. The biome would be restored to a reference point. This might require the reintroduction of appropriate megaherbivores like elephants, hippopotami, and rhinoceri, and top predators like lions.

We have not explicitly considered interactions with other global change drivers (e.g. catastrophic climate change might lead to a collapse of civilisation), but recognise that such factors might be the ultimate drivers of what happens

First, we consider “Collapse of civilisation, but no return to Eden”. In this scenario, a disastrous event (or series of events) leads to the extinction of Homo sapiens, or, of more specific relevance to biological invasions, leads to a situation where there is no longer an advanced civilisation that is capable of the inter-continental dispersal of species in a manner akin to either mass dispersal or cultivation (Wilson et al. 2009). The consequences of existing biological invasions would play out in full (Rouget et al. 2016), but there would be no new human-mediated introductions (or the few that occur would be akin to natural dispersal).

Second, global trade and transport continue to accelerate, and the rate of introduction of species and the subsequent invasions are not (possibly cannot) be controlled. Biogeographical barriers become fully eroded such that there is essentially global dispersal—the Earth could then be considered as a single continent from a biogeographic perspective. The concept of a “New Pangea” has a long pedigree, with some of the potential consequences codified by Rosenzweig (2001). In this scenario, local variation disappears and biotic homogenisation associated with globalisation becomes complete. This scenario has been termed a World of Weeds (Quammen 1998), although it is important to note that the New Pangea would also consist of globalised crops, livestock, and pets (McKinney 2005). Indeed, the beginnings of this can be seen with the globalisation of agriculture. For example, a McDonald’s hamburger with a coffee contains at least 19 plant species from all of the eight global centres of cultivated plant diversity identified by Vavilov (1926). All of these species are cultivated all around the world (Procheş et al. 2008b). However, the lack of effort to retain or protect non-utilitarian species and natural biogeographic distributions would lead to steep declines in biodiversity at a global scale.

Third, we consider a scenario that is somewhat similar to the Earth we know today—“Preserve or Use”. The Earth is divided into broad use types: areas that are transformed; areas used for sustainable agriculture, forestry production, or harvesting (e.g. fishing); and natural areas that are protected. Current levels of protection vary—around 14.7% of land area and 4.1% of the oceans are formally protected (UNEP-WCMC and IUCN 2016). This does not mean that such areas are devoid of alien species (Foxcroft et al. 2013) or that the eradication of alien species from such areas is possible or in some cases desirable—a third of all formally protected land is still subjected to intense human pressures (Jones et al. 2018). There are also significant moves to ensure that biodiversity is appreciated and considered everywhere. For example, in urban ecosystems the native/alien dichotomy is but one of many factors considered when formulating management strategies for “the whole landscape” (Hobbs et al. 2014; Potgieter et al. 2020, Chap.  11). Nonetheless, the distinction between alien and native is important and should be made explicit if biodiversity is to be conserved (Pauchard et al. 2018). This scenario requires a societal consensus that persists over time (e.g. in a “Preserve or Use” Earth a sense of enormous well-being is gained both by conserving native wildlife and by feeding the pigeons and sparrows too). The overall area that should be set aside is the subject of on-going debate, with recent proposals suggesting it should be as high as 50% (Buscher et al. 2017; Noss et al. 2012; Wilson 2016).

Although Earth is currently in a “Preserve and Use” state, we do not consider this scenario to be the status quo as we do not believe the current situation is sustainable. While some progress has been made controlling biological invasions, especially in protected areas (Foxcroft et al. 2013) and on islands (Greve et al. 2020, Chap.  8; Jones et al. 2016), problems with invasions are worsening in most cases (Millenium Ecosystem Assessment 2005), and globally the number of alien species that naturalise and become invasive in new areas keeps climbing, with no indication that it will plateau soon for most taxonomic groups (Seebens et al. 2017). Based on current drivers, we believe we are drifting towards the New Pangea.

Finally, we propose a “Conservation Earth” scenario in which the whole planet is conserved as a ‘cradle of life’. Human-mediated dispersal of organisms stops; invasions are eradicated; other human-mediated drivers of global change are reversed; and the Earth is actively restored to how it was before widespread human influence (including before biological invasions). For this scenario to be realised, humans would need to have developed radically advanced technologies in ecological restoration; there would need to be profound modifications to current biodiversity (from genes to ecosystems) and physico-chemical processes (e.g. the creation of soils); and the impact of humans on Earth (i.e. their footprint) would have to decline to negligible levels. However, once “Conservation Earth” was achieved, further human interventions could cease. This is perhaps the most sci-fi of our four long-term scenarios, but it is compatible with, and perhaps a likely outcome of, two of Baum et al. (2019)’s trajectories for human civilisation—the technological transformation trajectories, and the astronomical trajectories.

There is somewhat of a continuum between “New Pangea” and “Conservation Earth”, with “Preserve or Use” as an intermediate and possibly unstable state. There are, however, some qualitative differences. “Preserve or Use” differs from “New Pangea” in the retention of significant historical biogeographical patterns (e.g. Australia has a unique recognisable fauna, and the fishes of the Amazon are distinct from those of the Mekong or the Nile). “Preserve or Use” differs from “Conservation Earth” in the constant need for human intervention to ensure sustainability while maintaining biosecurity. Notably, if civilisation were to collapse, we suspect that it might already have moved significantly towards a “New Pangea” scenario. Therefore, while under both “Collapse of civilisation, but no return to Eden” and “Conservation Earth” there might be few if any humans left on Earth, these scenarios would look very different in terms of biogeography.

These scenarios are also not exhaustive, and we acknowledge that they deal with the interaction of global change drivers rather crudely. For example, climate change alone might lead to a complete reorganisation of the world’s biomes. These novel biomes might be distinct and separated by biogeographical barriers maintained by future civilisations, and so might be valued both for their intrinsic uniqueness and their utilitarian value. We feel, however, that the four potential futures we outline are useful as they provide a small set of different trajectories against which current events and decisions in biological invasions can be assessed.

31.3 The Year 2070: What Will Biological Invasions Look Like in South Africa When Children Born Today Are the Decision Makers?

In considering what South Africa might look like 50 years from now we considered five main themes that have emerged from recent horizon-scanning exercises in invasion science (Caffrey et al. 2014; Dehnen-Schmutz et al. 2018; Ricciardi et al. 2017): technological advances; the political socio-economic milieu; trade; the link to global change drivers; and potential evolutionary and ecological responses. We tried to envisage potential changes, and how these might influence biological invasions consistent with one of the long-term scenarios [excluding the collapse of civilisation scenario where the influence of catastrophic events on biological invasions would be irrelevant compared to the catastrophe itself] (Table 31.2). These projections are our own, but were inspired by horizon scanning; studies of the current and future trends in the Anthropocene; and deliberations during a 1-day workshop entitled “Where to with invasion science in South Africa?” organised by the Centre for Invasion Biology (CñIñB) in November 2018.
Table 31.2

How changes over the next 50 years in technological advances; the political socio-economic milieu; trade; global change drivers; and evolutionary and ecological responses might place biological invasions in South Africa along a trajectory to one of the scenarios outlined in Table 31.1


Possible causes

Possible outcomes

Potential examples for South Africa

2070 towards “New Pangea”

Technological: Lack of investment to improve technologies to control invasive species/existing effective control technologies (e.g. herbicides) are banned.

Management is either ineffective or infeasible leading to large areas of land dominated by invasive species of low value. The costs of restoring ecosystem functioning (e.g. soils) means that restoring these ‘invasion bad-lands’ is uneconomical.

Biotechnological solutions are available to produce sterile forestry trees but the use of such technology is currently disincentivised, e.g. by the Forest Stewardship Council standards that do not allow genetically modified organisms (Brundu and Richardson 2016). Similarly, a reluctance to use biological control to combat pines means that pine invasions continue unabated (Hoffmann et al. 2011).

The lack of a functioning process to approve pesticides effectively becomes a moratorium [e.g. delays in the approval of corvicides mean attempts to eradicate invasive birds fail (Davies et al. 2020, Chap.  22)].

Socio-political: Conflicts of interest and denialism prevent regulation and management. Government priorities shift from biosecurity and biological invasions to what are perceived as more immediate concerns.

Previously demarcated protected areas are eroded by invasions to the point where they cannot conserve local biodiversity.

Alien and native species receive the same existential rights in law, leading to a cessation in efforts to control invasions.

Access to private properties to control incursions is denied, and the rate of new invasions accelerates.

A lack of collaboration between South Africa and its geographic neighbours leads to the establishment of new invasions that subsequently cross the border [e.g. alien freshwater crayfish established in Swaziland when permits to culture them in South Africa were refused (Nunes et al. 2017)].

Trade: There is an acceleration and escalation, without concomitant international agreements or regulations.

Propagule pressure increases significantly, together with the establishment and invasion of many new species.

Facultative symbionts, not previously present, are introduced, and allow species to spread (Le Roux et al. 2020, Chap.  14).

Pests of agricultural crops have global distributions, requiring significant control measures and precluding particular crop genotypes. Some monocultural production become unsustainable due to global pathogens (Wingfield et al. 2015).

A failure in regional biosecurity efforts would lead to significant increases in the rates of species spread between South Africa and the rest of Africa (Faulkner et al. 2017), with regional biosecurity determined by the weakest link.

The absence of appropriate mycorrhizal symbionts historically limited establishment and spread of Pinus species in South Africa; but widespread inoculation has effectively removed this barrier. Other alien plant taxa might similarly establish if missing mutualists are introduced (Richardson et al. 2000a).

Global change: Various drivers (e.g. habitat modification, over-harvesting, climate change) interact, such that the fundamental niches of many species shift dramatically.

Species shift in range, show adaptation, or decline.

It is increasingly difficult to define a species’ native range, and communities are almost all novel. The priority for conservation efforts shifts towards maintaining ecosystem functions and a few iconic species.

The suite of invasive species changes with elevated levels of nitrogen and carbon dioxide and changes to the climate (some invasive species decline in importance and others previously deemed of low risk become high risk). As a result, our ability to predict based on the history of invasiveness and impact elsewhere declines.

Native trees can establish and dominate in areas that were previously grassland or savanna, i.e. bush encroachment (Nackley et al. 2017). Similarly, the alien tree Schinus molle is widely planted but not yet widely naturalised. Under climate change, fynbos and grassland area are predicted to become more amenable to establishment, leading to more widespread invasions (Richardson et al. 2010).

Nitrogen deposition triggers regime shifts to alternative stable states allowing incursion and persistence of alien taxa (Richardson et al. 2000b).

Droughts will become more frequent in the Western Cape, and this effect will be compounded by invasive trees that reduce streamflow from catchments; water supply schemes will be more likely to fail, with serious economic and social consequences.

Ecological-evolutionary: The continuing introduction of new taxa disrupts existing food webs, creates novel community interactions, leads to rapid evolution, and creates opportunities for some species at the expense of others.

Co-xenic symbioses are unpredictable and enable previously innocuous species to become invasive, leading to invasional meltdown (Simberloff and Von Holle 1999).

There is continuing selection for “super” weeds and pests that grow fast and dominate.

Invasions accelerate in unpredictable ways as adaptations allow species to establish outside of their native niches.

Puccinia psidii, a South American myrtle rust fungus, is now commonly associated with alien eucalypt taxa in South Africa, but this pathogen has spilled over onto native forest Myrtaceae species in South Africa with as yet unknown impacts (Le Roux et al. 2020, Chap.  14).

Guttural toads have changed their physiology and behaviour in order to become established in a novel Mediterranean ecosystem after only 20 years (Vimercati et al. 2018).

2070 towards “Preserve or Use”

Technological: Substantial investment into research and development keeps pace with novel demands of invasive species.

Effective management approaches are accepted and used judiciously.

Active and passive surveillance allows incursions to be detected timeously and controlled before they become widespread invaders (Wilson et al. 2017).

Protected areas are kept largely clear of invasions.

Costs of management are kept within fiscally acceptable levels.

Species that were previously widespread invaders are brought under control.

CRISPR technology is licenced worldwide and proves to be a valuable tool in invasive species management in South Africa.

Application of widely available tools such as Google Earth (Visser et al. 2014) allows for monitoring linked to effective interventions.

Funding for research on biological invasions keeps pace with invasions.

Biological control reduces the spread of widespread invaders, and in essence stops the impact of some invasions (Henderson and Wilson 2017; Hill et al. 2020, Chap.  19).

Socio-political: Appropriate regulations are enacted for pathways, species, and sites, at all stages of the invasion continuum. Strategies to combat biological invasions are developed and implemented.

The management of biological invasions becomes strategic and cost-effective, leading to significant savings in resources.

The Working for Water programme could perhaps remain an unashamed job-provision focussed component of a broader national programme of focussed biological invasion management. Management could then be more agile, less tied to political agendas, and therefore more effective and professional, and better able to focus on priorities (van Wilgen and Wannenburgh 2016).

Government develops a policy, strategies are revised and adopted (Department of Environmental Affairs 2014), and interventions prioritised based on the return on investment and on how wide the benefits are (van Wilgen and Wilson 2018).

Trade: Regional co-operation allows for collaboration on biosecurity, and international agreements are developed in response to biological invasions.

Rigorous and reliable risk analyses are set as a standard for trade.

Biosecurity is bolstered at all South African and southern African border crossings in order to prevent new invasions. Improved levels of compliance from those associated with international trade leads to a reduction in overall colonisation pressure.

The number of undesired deliberate introductions declines close to zero.

The Ballast Water Convention is implemented in full (Lukey and Hall 2020, Chap.  18; Robinson et al. 2020, Chap.  9).

The Southern African Development Community facilitates greater biosecurity co-operation.

By understanding the mechanisms behind Cactaceae invasions (the presence of detachable fragments in particular) it is possible to identify and regulate species that pose a risk while allowing trade in species that pose an acceptable level of risk (Novoa et al. 2015, 2016b).

Global change: Habitat change is reduced or limited to areas already destroyed. Local species stocks can rebuild.

There would still likely be a significant extinction debt to be paid by species not in protected areas, with an increasing number of species that cannot survive in the matrix of used and changed habitats.

Naturally harvested stocks require protected areas to maintain breeding populations.

Some alien taxa that provide eco-system services would need to be replaced with new or modified varieties that can cope with the novel environments already set aside as “use” areas.

Red List Index is declining for many taxa in South Africa (Measey et al. 2019), but substantial proportions of biodiversity are covered by formal protection (Skowno et al. 2019).

Ecological-evolutionary: There is some biotic resistance to invasions.

Co-xenic symbioses are unpredictable and require rapid removal with substantial human capital investment.

Adaptations by novel alien species allow opportunities for using new aliens providing ecosystem services following sufficient human capital and technological investments to prevent invasions and maintain their control.


2070 towards “Conservation Earth”

Technological: Substantial advances in technology means the costs associated with management decrease dramatically. Sustainable energy and food solutions are developed and implemented.

The more efficient use of ecosystems leads to a considerably reduced agricultural footprint.

Technology and engineering solutions allow for mitigation and stabilisation of global change drivers.

More effective monitoring protocols result in enhanced tools for defining management priorities and strategies for interventions.

Significant advancements in habitat restoration allow invasions to be reversed. For example, Cape Town has an on-going large restoration project at the Blaauwberg Nature Reserve of a site that was previously a monoculture of Acacia saligna where different management approaches have been trialled (Holmes et al. 2012).


Socio-political: There are substantial shifts in cultural views that mean conserving Earth and preserving native biodiversity become top priority (e.g. via a new Green Deal type revolution).

More funding and support is provided for authoritarian interventions, e.g. the rigorous guarding of protected areas, and removal of alien species.

Horticultural and pet trades focus only on native species and keeping alien species outside of strict captivity stops.

There are fewer alien species so invasion debt drops dramatically.

There is already a shift in horticultural trends toward native species (Botha and Botha 2000), but a step-change in both awareness and compliance is needed (Novoa et al. 2016a; Shackleton and Shackleton 2016).

Trade: Trade is tightly regulated or curtailed to prevent the introduction of alien species. A precautionary principle is adopted throughout.

The introductions of new species and new genetic material ceases.

Recommendations given by Faulkner et al. (2020, Chap.  12) are strictly adhered to.

Global change: Global change drivers are reversed in order to regain control of planetary destiny. Any that still exist have no real effect on decisions.

Corridors between reserves are established to allow for natural gene-flow of wide ranging species.

Reductions in extreme events and human-caused disturbance reduce the opportunities for invasion.

The environmental factors promoting invasions (e.g. soils) are managed, and restoration achieved (Holmes et al. 2020, Chap.  23; Wilson et al. 2020, Chap.  13).

Ecological-evolutionary: Biotic resistance is stronger than anticipated. Greater adaptation by native biota so that the advantage of being alien is more transient than expected.

The competitiveness of invasive species declines rapidly in time since date of introduction.

This has yet to be shown in South Africa, but it is clear that evolution can be surprisingly rapid both in invasive species and in the response from native communities. For example, native insect herbivores might rapidly adapt to invasive plants reducing their rate of spread and competitiveness (though cf. Procheş et al. 2008a).

31.4 The Year 2025: What Will Biological Invasions Looks Like After the Next Funding/Political Cycle?

The choice of specific events over the next 5 years that are likely to happen or that are already happening (e.g. challenges to the current regulations) are our own, but as before were inspired by: the recent report on the national status of biological invasions in South Africa (van Wilgen and Wilson 2018); South Africa’s draft National Strategy on Biological Invasions (van Wilgen et al. 2014); the C∙I∙B’s strategic plan for 2025; and insights from the 2018 C∙I∙B workshop on “Where to with invasion science in South Africa?”. We found it difficult, however, to link these events to the long-term trajectories. Therefore we categorised events in terms of whether they are likely to cause biological invasions to worsen (consistent with “Pangea Earth”); keep invasions roughly static (“Preserve or Use”); or reduce the impacts seen (consistent with either “Preserve or Use” or “Conservation Earth”) (Table 31.3). We also selected and discuss events under themes that we feel operate over this time-scale—planning, regulation, funding, public support, and research.
Table 31.3

How changes over the next 5 years in planning, regulation, funding, public support, and research might place biological invasions in South Africa along a trajectory to one of the scenarios outlined in Table 31.1


Possible causes


Current examples from South Africa

2025: The extent and impacts of biological invasions increases. (“New Pangea”)

Planning: The lack of a policy on managing biological invasions in the country results in the lack of adoption and implementation of a clear strategy for dealing with the problem at a national level (Lukey and Hall 2020, Chap.  18). The planning, implementing, and review of existing control plans focus on inputs to control rather than the outcomes in terms of the biological invasions themselves.

Available resources are directed to random projects, with no clear goals

What management happens is either ineffective or exacerbates the problem.

“Most alien plant control projects in South Africa have been given goals for the amounts to be spent, the number of people to be employed, and the areas to be treated. Monitoring of progress has a focus on these goals, and there are typically no goals that describe desired outcomes in terms of reducing plant invasions to manageable levels, what those manageable levels would be, and how long it would take to achieve them.” (van Wilgen and Wilson 2018, p 117)

Regulation: Legal challenges to current regulations succeed, leading to the repeal or suspension of the national regulations (Box  1.1, van Wilgen et al. 2020, Chap.  1).

Inability to regulate the import of new species or to control those already here, means that the rates of introduction of new species that will become invasive increases.

The removal of a mandate for many government agencies and private individuals to manage biological invasions results in a reduction in control activities.

Proposals to amend the A&IS Regulations were published in January 2018 (Department of Environmental Affairs 2018), but as of October 2019 these have not been promulgated in part due to an ongoing legal challenge to the regulations.

Funding: Levels of funding for the management of biological invasions is substantially reduced.

Many existing control projects would be curtailed, with insufficient funds remaining to effectively manage the remaining projects.

Cuts in funding to provincial conservation authorities has led to a decrease capacity, and a concomitant reduction in activities to monitor and control alien species (Impson 2016).

Public support: Public support for interventions to combat biological invasions decreases sharply (e.g. due to a high-profile incident).

Landowners refuse access to their land, and do not adhere to notifications and regulations.

Social media campaigns become active and disrupt on-going control efforts.

Levels of motivation and satisfaction of people managing biological invasions declines radically.

Several civil action groups have arisen in and around Cape Town to oppose alien control. These include “Shout for Shade” (opposed to tree-felling) and “Friends of the tahrs” (van Wilgen 2012). People involved in animal control projects have been personally abused and received death threats (Davies et al. 2020, Chap.  22).

Research: Research funding ceases due to changes in government priorities or inefficiencies in the allocation of funds.

There is less research to support decision makers and managers.

Fewer graduates are exposed to invasion science, and the human capacity deficit increases.

There is less knowledge of the problem with which to motivate for funding or highlight the issues, leading to a negative feedback and further reductions in funding.

The Centre for Invasion Biology and the Centre for Biological Control depend on funding over 3–5 year cycles, and there is no guarantee that funding will continue (Hill et al. 2020, Chap.  19; Richardson et al. 2020a, Chap.  30).

Science councils, such as the CSIR, have adopted research strategies that focus on industrialisation, moving away from environmental and public-good research.

2025: Biological invasions stay constant (“Preserve or Use”)

Planning: A national policy on biological invasions is developed and a national strategy for dealing with biological invasions is implemented in principle if not formally adopted. Goals of management remain unclear, but efforts to track effectiveness are improved (e.g. in response to an audit query).

Scrutiny of management effectiveness highlights how management can be improved even in the absence of clear goals, and these recommendations begin to be implemented.

There is some monitoring feedback allowing management to adapt and improve, but this is still largely ad hoc.

Both the national strategy on biological invasions and the CAPE strategy on invasive species have been developed, but not formally adopted. Responsibility for adoption is not always clear, as many different government departments need to collaborate closely. However, both documents have been cited and read by managers.

Regulation: Legal framework remains as it is.

While there is some compliance, there are still many instances of non-compliance, leading to a mixed adherence to requirements.

The current regulations continue to have some impact, but not as much as desired.

Levels of compliance are generally low, though there are increasing numbers of examples of permits, compliance, and enforcement (van Wilgen and Wilson 2018). Capacity to comprehensively implement the regulations remains a challenge.

Funding: Funding levels fluctuate, but remain relatively constant in real terms.

The ability to carry out the necessary levels of control and follow-up continues. Spread of invasive species is curtailed, and losses of ecosystem services kept constant.

Government funding on work of biological invasions has increased steadily despite funding cuts in many other areas.

Public support: Public appreciation of the problem of biological invasions, their consequences, and potential solutions remains at relatively low levels.

Many people remain ignorant of the problem, or challenge the motivations put forward for control, and do not take regulations seriously. Other stakeholders engage with the problem and assist.

Various industries (e.g. horticulture) have shown a commitment to comply with the regulations, although levels are still low (Cronin et al. 2017). In addition, there is ongoing disagreement about the value of alien species from a range of sources (freshwater anglers, foresters, and those engaged in the pet trade).

Research: Research capacity is maintained due to renewal of existing funding.

Levels of understanding increase in line with issues. Management relies on existing, incomplete understanding, or trial-and-error approaches, but occasionally some real insight is provided. There are an increasing number of cases of uptake of research findings.

Currently, invasion science in South Africa is well funded, but this is under threat. There are a few collaborative research partnerships to encourage the flow of information between researchers and managers exist, but these are far from comprehensive (Foxcroft et al. 2020, Chap.  28).

2025: The impacts of biological invasion are reduced (“Preserve or Use”/“Conservation Earth”)

Planning: A national policy on biological invasions sets out a vision for what can be achieved and leads to a strategy with clear goals that is adopted and implemented. In consequence management plans are developed for pathways, species, and sites.

Managers and decision-makers have a clear agreed vision of how biological invasions are to be dealt with.

A monitoring program, focussed on clear goals, helps management to become more adaptive.

Increased achievement of management goals leads to a reduction in impacts, or at least slows the rate of growth in impacts.

A national policy processes has recently been proposed. Various planning tools are available including a strategy and guidelines for management (Department of Environmental Affairs 2014, 2015). A framework of indicators is available to facilitate tracking progress in terms of the outcomes (Wilson et al. 2018).

Regulation: The regulatory framework is improved, and capacity to manage the implementation of regulations is increased.

Improved compliance and management of biological invasions, and reduced contestations; more resources from additional stakeholders directed to management; and increased control efforts reduce the extent of invasions over large areas leading to a reduction in impacts.

While the process has been initially slow, permits, notifications and directives are being issued (van Wilgen and Wilson 2018), as more criminal cases are successful prosecuted, people will be more motivated to comply.

A risk analysis framework to provide evidence to support listing of alien species has been developed (Kumschick et al. 2018, 2020). If formally adopted, it could provide a transparent process and hopefully reduce legal contestations.

Funding: Levels of funding to manage biological invasions are increased.

The prospects for achieving control in priority areas is improved.

The loss of ecosystem services from priority areas is reduced.

Currently, relatively generous funding is available, considering the demands on the South African fiscus.

Public support: Public awareness and appreciation of the problem increases, as part of an overall increase in environmental awareness through successful outreach activities and as part of a general global increase in awareness (e.g. through the Extinction Rebellion).

Increased understanding of biological invasions leads to improvements in management.

Increased achievement of goals leads to a reduction in impact, or a slowing in the rate of growth in impacts.

Several volunteer-type organisations in South Africa increase or supplement management capacity. These include “hack” groups, honorary rangers, and citizen scientists who contribute observations through platforms like iNaturalist. These could increase in number and effectiveness as awareness grows.

Research: Government sees invasion science as a key research need and opportunity for human capacity development in applied sciences and for greater regional research co-operation.

Political support for increased funding, and increased compliance with regulations.

The extent of invasions over larger areas is further reduced, leading to a reduction in impacts.

Regional research collaboration increases, perhaps through the auspices of the Southern African Development Community.

The establishment of a government funded Centre for Invasion Biology (Richardson et al. 2020a, Chap.  30), and a team focusing on biological invasions based at the South African National Biodiversity Institute (Wilson et al. 2013), highlights the government’s appreciation of biodiversity and the need to undertake research on drivers of biodiversity loss.

31.5 Possible Ways Forward: Examples from South Africa

God, grant me the serenity to accept the things I cannot change,

courage to change the things I can,

and wisdom to know the difference.

The Serenity Prayer (Reinhold Niebuhr)

In this chapter, we have outlined four long-term scenarios, and have described how events over the next 5–50 years will place us on a trajectory to one of these. Which end point is desirable is a choice for society, and some of the issues are highly contentious and incompatible [e.g. the right of your neighbour to keep a pet cat in their garden affects your right to enjoy a diversity of birds in your garden (Potgieter et al. 2020, Chap.  11)]. Such issues can, of course, also vary over space and time. Introduced species might increase local diversity over the short-term but reduce global diversity and even local diversity over longer time frames, due to the interplay between invasion and extinction debts (Rouget et al. 2016; Tilman et al. 1994). We illustrate these scenarios not to proselytise, but to highlight how the choices we make now could influence the future state of the Earth and what options (if any) are available to future generations.

Importantly, business-as-usual will ensure that current trends continue and that biological invasions will worsen due to an increasing number of alien species, growth in the extent of invasions, increasing impacts, and the continuing problems around conflict-generating species, ineffective management, and insufficient management capacity (van Wilgen and Wilson 2018). There are few studies on the impacts of alien species but available studies show that the reductions in the value of ecosystem services, productivity of rangelands, and in biodiversity intactness caused by alien species are low at present, but expected to grow rapidly (van Wilgen et al. 2008; Zengeya et al. 2020, Chap.  17). The challenge in South Africa will be to combine the current funding model (where most government funding to manage biological invasions is primarily for job creation), with one that also focuses on improving the efficiency of management and the outcomes in terms of reduced impacts and threats from invasions (van Wilgen and Wannenburgh 2016). Shifting our focus from control to prevention would also improve returns on investment, but siphoning funds from current problems might exacerbate them. Practicing conservation triage, with a focus on priority areas, could lead to patchy successes, but is likely to meet stiff resistance as people are reluctant to admit that some areas have to be abandoned to save others. Similarly, the distribution of funding has been based on political and social concerns (e.g. the desire to spread funding across the country). Shifting this to a funding system based on ecological and environmental needs would be unpopular and might see a decline in political support and ultimately funding. Increasing investment in biological control would also increase returns on investment (Hill et al. 2020, Chap.  19), but is less politically attractive as it is not labour-intensive. Important questions remain unanswered. What will be required to turn this around, and will it be politically possible? What is the future of South Africa’s legislative framework in the face of legal challenges (cf. Lukey and Hall 2020, Chap.  18)? There are, however, plenty of examples where change is possible. Continuing investment in the management of biological invasions can be both vital for sustainable and equitable development and cost-effective, especially if economic incentives for invasive species management and overall restoration are implemented (Milton et al. 2003). Regardless of the trajectory and how we deal with the issue, we expect that in 50 years’ time the most widespread invaders that cause the most impacts will be similar to those that occur now [for comparison, invasions in the Fynbos Biome are largely, though not entirely, the same as those 70 years ago with acacias, hakeas and pines dominating (van Wilgen et al. 2016)]. However, there will inevitably be some big surprises (e.g., the discovery of the Polyphagous Shot-Hole Borer, Paap et al. 2018; Box  11.3, Potgieter et al. 2020, Chap.  11).

South Africa as a society will need to make decisions as to what and how to prioritise for management. In the rest of this chapter we outline selected case-studies from this book to illustrate how decisions made over the next 5–50 years will determine the trajectory of biological invasions in the future.

31.5.1 Coastal vs. Off-Shore Ecosystems

Most of South Africa’s rocky seashore has been transformed by the introduction of alien mussel species. This was not a deliberate choice and no technologies currently exist to alter this situation (Robinson et al. 2020, Chap.  7). The novel ecosystems created by these invasions have some benefits, and interesting impacts on biodiversity (Griffiths et al. 1992; Robinson et al. 2020, Chap.  7). Despite the current regulations, it will be difficult, but not impossible, to prevent new invasions of coastal species. There are also moves to protect large areas from habitat transformation. All this suggests that, for coastal systems, we are in a “Preserve or Use” state that is much closer to “New Pangea” than “Conservation Earth”. In sharp contrast, very few off-shore marine invasions have been recorded, and there are no examples of invasive marine fish in South Africa. It might be possible to preserve this situation, and stay on a trajectory closer to “Conservation Earth”, though this depends on the degree to which a sustainable blue economy can be achieved without leading to more species introductions and more impacts.

31.5.2 The Management of Invasions in Arid Rangelands: Prosopis Species

A large proportion of the land surface of South Africa is taken up by arid rangelands (Table  16.1, O’Connor and van Wilgen 2020, Chap.  16). These rangelands are being threatened by rapidly-expanding invasions of Mesquite (Prosopis) trees that reduce groundwater resources on which many towns and communities in the region are dependent (Le Maitre et al. 2020, Chap.  15), and reduce the capacity of rangelands to produce livestock. If Prosopis invasions continue to increase, there could be total economic collapse in these regions, similar to that experienced in the Karoo in the 1920s as a result of invasion by Opuntia ficus-indica (Mission Prickly Pear) (O’Connor and van Wilgen 2020, Chap.  16). There is a need to diversify land-use activities to increase income in these areas, for example by combining livestock farming with game viewing, hunting and tourism (Milton et al. 2003). If successful, some of the income could be channelled back into Prosopis control. There are also initiatives that will explore the possibility of triple bottom-line accounting, and using this to underpin a system of tax incentives to allow landowners to recoup the costs of alien plant control. This, combined with more effective biological control, could reverse the negative trend in Prosopis invasions. Currently, however, we are in a “Preserve or Use” state that is shifting rapidly towards “New Pangea”, and if the similar on-going Prosopis invasions in Kenya and Ethiopia continue, many of these landscapes will become physically and functionally identical (and provide few ecosystem services).

31.5.3 The Need for Taxonomic Services and Well-Curated Comprehensive Lists of Alien Species

The status of knowledge of alien species varies markedly—high for mammals (Measey et al. 2020, Chap.  5), lower for plants (Richardson et al. 2020b, Chap.  3), lower still in marine systems (Robinson et al. 2016, 2020, Chap.  9), and almost non-existent for many soil and microbial groups (Janion-Scheepers et al. 2016; Wood 2017). But even for well-studied groups, there are errors and omissions in the lists of invasive species (Magona et al. 2018). South Africa lacks a comprehensive consolidated list of alien taxa (cf. van Wilgen and Wilson 2018). This is a problem as many alien species that are known invaders elsewhere in the world are present in South Africa but not yet incorporated into long-term planning and strategies. Continuing investment in taxonomy would increase our ability to identify and respond to incursions before they become widespread, and understanding the target species can be essential for management (Jacobs et al. 2017; Pyšek et al. 2013). By contrast, a dramatic reduction in research funding would see lists quickly become out of date which would undermine both risk analysis efforts (Kumschick et al. 2020, Chap.  20) and public support. Taxonomic services and alien species lists provide the foundational biodiversity information necessary for us to be able to choose between a “New Pangea” or “Conservation Earth” trajectory.

31.5.4 Regulatory Directions

South Africa is one of the few countries that has comprehensive regulations in place to manage biological invasions, and many parts of the regulations are innovative (van Wilgen and Wilson 2018). While this is certainly commendable, there are many challenges to the effective implementation of these regulations, not least of which is a lack of capacity to monitor and, if necessary, enforce them. Section  18.8.2 of Lukey and Hall (2020, Chap.  18) highlights that compliance with the regulations by 90% of society will only be achieved if the 10% that do not comply are brought to book, which is not the case at present. Compliance will also only be achieved if the regulations are broadly regarded as just and equitable; this may not be the case with the current approach of “faultless liability” whereby landowners are responsible for the control of species they did not introduce. Currently, the regulations are either ignored, or people are unaware of them (van Wilgen and Wilson 2018), and some people have mounted legal challenges to them (Lukey and Hall 2020, Chap.  18). If the regulations remain ineffective, or are removed as a result of legal challenges, we may be heading towards “New Pangea”. A change in approach might be required to move in other directions, including subsidies and tax breaks, but a major step would be the development of a national policy on biological invasions to provide the basis for strategic and regulatory developments.

31.5.5 A New Green Deal and Landscape Stewards

The idea of linking environmental management to employment creation (i.e. labour-intensive alien plant clearing programmes) was an innovative solution to the need to raise funds for invasive plant control in South Africa in the post-apartheid consensus (when funds were also desperately needed for education, health, infrastructure development, security, and welfare). However, the management of invasions is still tied primarily to welfare and job creation, and while the allocation of funds has grown, managers are still assessed on input indicators (e.g. numbers of jobs created, and money spent) rather than output or outcome indicators (e.g. reductions in the area invaded and the impacts caused) (Wilson et al. 2018). Moreover, the approach limits the implementation of more effective high-tech solutions in some cases (van Wilgen and Wilson 2018). This “green deal” has thus failed to stem the spread of invasive species at a national scale, and business-as-usual would set us on a trajectory towards “New Pangea”. A combination of a new green deal and a ‘landscape steward’ approach could reverse these trends. More effective, goal-directed planning and implementation supported by a greater focus on training on project management and monitoring control effectiveness, and judicious use of new technologies (e.g. drones, precision control, DNA barcoding, remote sensing and monitoring, and improved taxonomic capacity), could improve management effectiveness and returns on investment. Continuous monitoring and maintenance of project outcomes as well as the development of nuanced interventions that are appropriate for the specific context would be more realistic if a more permanent connection is made between managers and the land they are managing, e.g. through a landscape steward type approach.

This would require a societal consensus around the need to avoid the longer-term impacts associated with invasions (i.e. beyond current political and funding cycles); the need to balance all the benefits of invasions (timber, fuel, fodder, carbon, food and recreation) against their negative impacts (on water, rangeland productivity, biodiversity, fire hazard and human health); an appreciation of the threat invasions pose to economic and social prospects and ultimately sustainable development; and an increased focus on supporting bottom-up community driven connections to the land that is being managed. But the idea of linking environmental sustainability and job creation is as valid now as it was 25 years ago. A new green deal based on explicit and commonly shared goals of environmental and social sustainability would set South Africa on the path to “Preserve and Use”, and ultimately to ensure that South Africa retains its unique character.

31.6 Conclusions

It’s hard to make predictions, especially about the future.

Provenance uncertain, probably Danish (made famous by Niels Bohr)

While efforts to predict invasions are becoming more sophisticated (e.g., Essl et al. 2019; Gallien et al. 2019) and metrics exist for projecting how current indicators might change over time (Rouget et al. 2016; Wilson et al. 2018), scenarios for biological invasions will remain uncertain, particularly over longer time horizons. Most projections are implicitly or explicitly based on experience with invasions in the recent past. Conditions, including many drivers of invasions, are changing rapidly. Uncertainties are implicit in invasion science and will be best dealt with by clearly circumscribing invasion phenomena, measuring and providing clear evidence for such phenomena, and understanding their drivers and the mechanisms that generate consequences (Latombe et al. 2019). In the last section, we highlighted a few of the things that, for future generations to continue to have the choice of which scenario they want, will likely be needed: different priorities for different ecosystems (e.g. coastal vs. off-shore); the development and implementation of strategies for particular invasions (e.g. for Prosopis invasions); improvements in our foundational knowledge (e.g. through well-curated and comprehensive lists of alien species); a wide range of regulatory and other policy approaches; and novel ways to facilitate land management. However, it seems likely to us that in the next 200–2000 years we will reach a point when either the concept of biological invasions is irrelevant; invasions continue to be managed in the context of complex competing needs and interests; we have advanced to a stage where we can turn Earth as a whole into a biodiversity reserve; or civilisation collapses. We believe that the policy and management decisions we make over the coming years and decades will set us on one of these trajectories (Figs. 31.1 and 31.2). If we can develop a shared vision of how we want South Africa to look (e.g. a national policy on biological invasions), then this will provide us with a focal point for our efforts.
Fig. 31.1

A schematic showing the themes discussed in this chapter, i.e. how events and drivers over the next 5–50 years might place us on a trajectory towards “New Pangea”, “Preserve or Use”, or “Conservation Earth”. We have not included events that might lead to “Collapse of civilisation but no return to Eden” as these are often typified by unpredictable events not directly related to invasions; suffice to say that if civilisation were to collapse the impacts of invasions on biodiversity and biogeographic processes would not cease

Fig. 31.2

Photographs illustrating potential futures of biological invasions in South Africa taken from the Western Cape in areas close to Stellenbosch. In the panels next to each photograph, the outlines of different species or vegetation types are numbered, and coloured according to whether they represent native, alien, or cultivated. (a) South Africa is transformed to a novel ecosystem composed largely of alien species (“Collapse but no return to a Garden of Eden”). (1) Acacia saligna, (2) Pinus sp., (3) Leptospermum laevigatum, and (4) a Restionaceae. The photo was taken near Betty’s Bay by Brian van Wilgen. (b) The landscape is composed of a matrix of utilised areas and invaded areas that have little if any conservation value in terms of native species (“New Pangea”). (1) Acacia saligna; (2) Carpobrotus sp.; (3) a wheat field. The photo was taken on the Agulhas Plain by John Measey. (c) The landscape is composed of a matrix of utilised areas and areas that have significant conservation value in terms of native species (“Preserve or Use”). (1) A mix of vegetation types including Kouebokkeveld Shale Fynbos, North Hex Sandstone Fynbos, and Altimontane Sandstone Fynbos; (2) Eucalyptus sp. planted close to a homestead; (3) agricultural land; (4) Ceres Shale Renosterveld. The photograph was taken close to Ceres by John Wilson. (d) The unique vegetation of South Africa is conserved for future generations and natural per-human ecosystem processes are allowed to continue (“Conservation Earth”). (1) Agulhas limestone fynbos; (2) Protea compacta in flower; (3) Leucadendron sp.; (4) a Restionaceae. The photograph was taken near Betty’s Bay by Brian van Wilgen



We acknowledge support from the DSI-NRF Centre of Excellence for Invasion Biology (C∙I∙B) and the South African Department of Environment, Forestry, and Fisheries (DEFF) 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. We thank Franz Essl, Guillaume Latombe, and Peter Lukey for insightful comments on an early version; and our colleagues at the C∙I∙B, the SANBI, and other institutions who shared insights and ideas, especially during a workshop on “Where to with invasion science in South Africa?” in November 2018.


  1. Baum SD et al (2019) Long-term trajectories of human civilization Foresight 21:53–83. CrossRefGoogle Scholar
  2. Botha C, Botha J (2000) Bring back nature to your garden. Wildlife and Environmental Society of South Africa, KwaZulu-Natal Region, DurbanGoogle Scholar
  3. Brand S (2008) The clock of the long now: time and responsibility. Basic Books, New YorkGoogle Scholar
  4. Brundu G, Richardson DM (2016) Planted forests and invasive alien trees in Europe: a code for managing existing and future plantings to mitigate the risk of negative impacts from invasions. Neobiota 30:5–47. CrossRefGoogle Scholar
  5. Buscher B et al (2017) Half-earth or whole earth? Radical ideas for conservation, and their implications. Oryx 51:407–410. CrossRefGoogle Scholar
  6. Caffrey JM et al (2014) Tackling invasive alien species in Europe: the top 20 issues management of biological invasions. 5:1–20.
  7. Cronin K, Kaplan H, Gaertner M, Irlich U, Hoffman MT (2017) Aliens in the nursery: assessing the attitudes of nursery managers to invasive species regulations. Biol Invasions 19:925–937. CrossRefGoogle Scholar
  8. Davies SJ et al (2020) Experience and lessons from alien and invasive animal control projects in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 625–660.
  9. Deacon J (1986) Human settlement in South Africa and archaeological evidence for alien plants and animals. In: Macdonald IAW, Kruger FJ, Ferrar AA (eds) The ecology and management of biological invasions in southern Africa. Oxford University Press, Cape Town, pp 3–19Google Scholar
  10. Dehnen-Schmutz K et al (2018) Alien futures: What is on the horizon for biological invasions? Diversity Distrib 24:1149–1157. CrossRefGoogle Scholar
  11. Department of Environmental Affairs (2014) A national strategy for dealing with biological invasions in South AfricaGoogle Scholar
  12. Department of Environmental Affairs (2015) Monitoring, control & eradication plans: guidelines for species listed as invasive in terms of Section 70 of National Environmental Management: Biodiversity Act, 2004 (act no. 10 of 2004) (NEM:BA) and as required by Section 76 of this Act. South African GovernmentGoogle Scholar
  13. Department of Environmental Affairs (2018) National Environmental Management: Biodiversity Act 2004 (Act No. 10 of 2004) Draft Amendments to the Alien and Invasive Species Lists, vol 97. Government Gazette of South Africa, PretoriaGoogle Scholar
  14. Essl F et al (2019) Introducing AlienScenarios: a project to develop scenarios and models of biological invasions for the 21st century. NeoBiota 45:1–17. CrossRefGoogle Scholar
  15. Faulkner KT, Hurley BP, Robertson MP, Rouget M, Wilson JRU (2017) The balance of trade in alien species between South Africa and the rest of Africa Bothalia: African biodiversity and conservation 47:a2157. CrossRefGoogle Scholar
  16. Faulkner KT et al (2020) South Africa’s pathways of introduction and dispersal and how they have changed over time. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 311–352.
  17. Foxcroft LC, Pysek P, Richardson DM, Genovesi P (eds) (2013) Plant invasions in protected areas: patterns, problems and challenges, vol 7. Springer, DordrechtGoogle Scholar
  18. Foxcroft LC, van Wilgen BW, Abrahams B, Wannenburgh A, Esler KJ (2020) Knowing-doing continuum or knowing-doing gap? Information flow between researchers and managers of biological invasions in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 827–850.
  19. Gallien L, Thornhill AH, Zurell D, Miller JT, Richardson DM (2019) Global predictors of alien plant establishment success: combining niche and trait proxies. Proc R Soc B Biol Sci 286.
  20. Greve M, Eric C, von der Meden O, Janion-Scheepers C (2020) Biological invasions in South Africa’s offshore sub-Antarctic territories. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 205–226.
  21. Griffiths CL, Hockey PAR, van Erkom Schurink C, Le Roux PJ (1992) Marine invasive aliens on South African shores: implications for community structure and trophic functioning S Afr J Mar Sci 12:713–722Google Scholar
  22. Henderson L, Wilson JRU (2017) Changes in the composition and distribution of alien plants in South Africa: an update from the Southern African Plant Invaders Atlas (SAPIA). Bothalia: Afr Biodivers Conserv 47:a2142. CrossRefGoogle Scholar
  23. Hill MP et al (2020) More than a century of biological control against invasive alien plants in South Africa: a synoptic view of what has been accomplished. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 549–568.
  24. Hobbs RJ et al (2014) Managing the whole landscape: historical, hybrid, and novel ecosystems. Front Ecol Evol 12:557–564. CrossRefGoogle Scholar
  25. Hoffmann JH, Moran VC, van Wilgen BW (2011) Prospects for the biological control of invasive Pinus species (Pinaceae) in South Africa. Afr Entomol 19:393–401CrossRefGoogle Scholar
  26. Holmes PM, Rebelo AG, Dorse C, Wood J (2012) Can Cape Town’s unique biodiversity be saved? Balancing conservation imperatives and development needs. Ecol Soc 17:12. CrossRefGoogle Scholar
  27. Holmes PM et al (2020) Biological invasions and ecological restoration in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 661–696.
  28. Impson ND (2016) Have our provincial aquatic scientists become critically endangered? Water Wheel 15:20–23Google Scholar
  29. Jacobs LEO, Richardson DM, Lepschi BP, JRU W (2017) Quantifying errors and omissions in the listing of alien species: Melaleuca in South Africa as a case-study. Neobiota 32:89–105. CrossRefGoogle Scholar
  30. Janion-Scheepers C et al (2016) Soil biota in a megadiverse country: current knowledge and future research directions in South Africa. Pedobiologia 59:129–174. CrossRefGoogle Scholar
  31. Jones HP et al (2016) Invasive mammal eradication on islands results in substantial conservation gains. Proc Natl Acad Sci 113:4033–4038. CrossRefPubMedGoogle Scholar
  32. Jones KR et al (2018) One-third of global protected land is under intense human pressure. Science 360:788+. CrossRefPubMedGoogle Scholar
  33. Kumschick S, Wilson JR, Foxcroft LC (2018) Framework and guidelines for conducting risk analyses for alien species. Preprints.
  34. Kumschick S, Foxcroft LC, Wilson JR (2020) Analysing the risks posed by biological invasions to South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 569–592.
  35. Latombe G et al (2019) A four-component classification of uncertainties in biological invasions: implications for management. Ecosphere 10:e02669. CrossRefGoogle Scholar
  36. Le Maitre DC et al (2020) Impacts of plant invasions on terrestrial water flows in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 429–456.
  37. Le Roux JJ et al (2020) Biotic interactions as mediators of biological invasions: insights from South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 385–428.
  38. Lukey P, Hall J (2020) Biological invasion policy and legislation development and implementation in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 513–548.
  39. Magona N, Richardson DM, Le Roux JJ, Kritzinger-Klopper S, JRU W (2018) Even well-studied groups of alien species might be poorly inventoried: Australian Acacia species in South Africa as a case study. NeoBiota 39:1–29. CrossRefGoogle Scholar
  40. McKinney ML (2005) New Pangea: homogenizing the future biosphere. Proc Calif Acad Sci 56:119–129Google Scholar
  41. Measey J, Hui C, Somers M (2020) Terrestrial vertebrate invasions in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 113–150.
  42. Measey J et al (2019) Has strategic planning made a difference to amphibian conservation research in South Africa? Bothalia 49:a2428.
  43. Millenium Ecosystem Assessment (2005) Ecosystems and human well-being: synthesis. Island Press, Washington, DCGoogle Scholar
  44. Milton SJ, Dean WRJ, Richardson DM (2003) Economic incentives for restoring natural capital in southern African rangelands. Front Ecol Evol 1:247–254.[0247:eifrnc];2 CrossRefGoogle Scholar
  45. Nackley LL, West AG, Skowno AL, Bond WJ (2017) The nebulous ecology of native invasions. Trends Ecol Evolut 32:814–824. CrossRefGoogle Scholar
  46. Noss R et al (2012) Bolder thinking for conservation. Conserv Biol 26:1–4CrossRefGoogle Scholar
  47. Novoa A, Kaplan H, Kumschick S, Wilson JRU, Richardson DM (2015) Soft touch or heavy hand? Legislative approaches for preventing invasions: insights from Cactaceae in South Africa. Invas Plant Sci Manage 8:307–316. CrossRefGoogle Scholar
  48. Novoa A, Kaplan H, Wilson JRU, Richardson DM (2016a) Resolving a prickly situation: involving stakeholders in invasive cactus management in South Africa. Environ Manag 57:998–1008. CrossRefGoogle Scholar
  49. Novoa A, Kumschick S, Richardson DM, Rouget M, Wilson JRU (2016b) Native range size and growth form in Cactaceae predict invasiveness and impact. Neobiota 30:75–90. CrossRefGoogle Scholar
  50. Nunes AL, Zengeya TA, Measey GJ, Weyl OLF (2017) Freshwater crayfish invasions in South Africa: past, present and potential future. Afr J Aquat Sci 42:309–323. CrossRefGoogle Scholar
  51. O’Connor T, van Wilgen BW (2020) The impact of invasive alien plants on rangelands in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 457–486.
  52. Paap T, de Beer ZW, Migliorini D, Nel WJ, Wingfield MJ (2018) The polyphagous shot hole borer (PSHB) and its fungal symbiont Fusarium euwallaceae: a new invasion in South Africa. Australas Plant Pathol 47:231–237. CrossRefGoogle Scholar
  53. Pauchard A et al (2018) Biodiversity assessments: origin matters. PLoS Biol e2006686:16. CrossRefGoogle Scholar
  54. Potgieter LJ et al (2020) Biological invasions in South Africa’s urban ecosystems: patterns, processes, impacts and management. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 273–310.
  55. Procheş Ş, Wilson JRU, Richardson DM, Chown SL (2008a) Herbivores, but not other insects, are scarce on alien plants. Austral Ecol 33:691–700CrossRefGoogle Scholar
  56. Procheş Ş, Wilson JRU, Vamosi JC, Richardson DM (2008b) Plant diversity in the human diet: weak phylogenetic signal indicates breadth. Bioscience 58:151–159CrossRefGoogle Scholar
  57. Pyšek P et al (2013) Hitting the right target: taxonomic challenges for, and of, plant invasions. AoB Plants 5:plt042. CrossRefPubMedCentralGoogle Scholar
  58. Quammen D (1998) Planet of weeds—tallying the losses of Earth’s animals and plants. Harper’s Magazine, October, pp 57–70Google Scholar
  59. Ricciardi A et al (2017) Invasion science: a horizon scan of emerging challenges and opportunities. Trends Ecol Evolut 32:464–474. CrossRefGoogle Scholar
  60. Richardson DM, Allsopp N, D’Antonio CM, Milton SJ, Rejmánek M (2000a) Plant invasions—the role of mutualisms. Biol Rev 75:65–93Google Scholar
  61. Richardson DM et al (2000b) Invasive alien species and global change: a South African perspective. In: Mooney HA, Hobbs RJ (eds) Invasive species in a changing world. Island Press, Washington, DC, pp 303–349Google Scholar
  62. Richardson DM et al (2010) Accommodating scenarios of climate change and management in modelling the distribution of the invasive tree Schinus molle in South Africa Ecography 33:1049–1061. CrossRefGoogle Scholar
  63. Richardson DM, Abrahams B, Boshoff N, Davies SJ, Measey J, van Wilgen BW (2020a) South Africa’s Centre for Invasion Biology: an experiment in invasion science for society. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 875–912.
  64. Richardson DM et al (2020b) The biogeography of South African terrestrial plant invasions. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 65–94.
  65. Robinson TB et al (2016) Lost in translation? Standardising the terminology used in marine invasion biology and updating South African alien species lists. Afr J Mar Sci.
  66. Robinson TB, Peters K, Brooker B (2020) Coastal invasions: The South African context. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 227–246.
  67. Rosenzweig ML (2001) The four questions: what does the introduction of exotic species do to diversity? Evol Ecol Res 3:361–367Google Scholar
  68. Rouget M et al (2016) Invasion debt—quantifying future biological invasions. Divers Distrib 22:445–456. CrossRefGoogle Scholar
  69. Seebens H et al (2017) No saturation in the accumulation of alien species worldwide. Nat Commun 8.
  70. Shackleton CM, Shackleton RT (2016) Knowledge, perceptions and willingness to control designated invasive tree species in urban household gardens in South Africa. Biol Invasions 18:1599–1609. CrossRefGoogle Scholar
  71. Simberloff D, Von Holle B (1999) Positive interaction of nonindigenous species: invasional meltdown? Biol Invasions 1:21–32CrossRefGoogle Scholar
  72. Skowno A et al (2019) National Biodiversity Assessment 2018: an assessment of South Africa’s ecosystems, species and genes. Synthesis Report. South African National Biodiversity Institute, an entity of the Department of Environmental Affairs, PretoriaGoogle Scholar
  73. Sutherland WJ, Woodroof HJ (2009) The need for environmental horizon scanning. Trends Ecol Evolut 24:523–527. CrossRefGoogle Scholar
  74. Tilman D, May RM, Lehman CL, Nowak MA (1994) Habitat destruction and the extinction debt. Nature 371:65–66. CrossRefGoogle Scholar
  75. UNEP-WCMC, IUCN (2016) Protected Planet Report 2016. UNEP-WCMC/IUCN, Cambridge/Gland, SwitzerlandGoogle Scholar
  76. van Wilgen BW (2012) Evidence, Perceptions, and trade-offs associated with invasive alien plant control in the Table Mountain National Park, South Africa. Ecol Soc 17.
  77. van Wilgen BW, Wannenburgh A (2016) Co-facilitating invasive species control, water conservation and poverty relief: achievements and challenges in South Africa’s Working for Water programme. Curr Opin Environ Sustain 19:7–17. CrossRefGoogle Scholar
  78. van Wilgen BW, Wilson JR (eds) (2018) The status of biological invasions and their management in South Africa in 2017. South African National Biodiversity Institute, Kirstenbosch and DST-NRF Centre of Excellence for Invasion Biology, StellenboschGoogle Scholar
  79. van Wilgen BW, Reyers B, Le Maitre DC, Richardson DM, Schonegevel L (2008) A biome-scale assessment of the impact of invasive alien plants on ecosystem services in South Africa. J Environ Manag 89:336–349CrossRefGoogle Scholar
  80. van Wilgen BW, Richardson DM, Wilson JR (2014) A national strategy for dealing with biological invasions in South Africa. Department of Environmental AffairsGoogle Scholar
  81. van Wilgen BW et al (2016) Ecological research and conservation management in the Cape Floristic Region between 1945 and 2015: history, current understanding and future challenges. Trans R Soc S Afr 71:207–303. CrossRefGoogle Scholar
  82. van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya T (2020a) Biological invasions in South Africa: an overview. Springer, Berlin, pp 3–30.
  83. van Wilgen NJ, van Wilgen BW, Midgley GF (2020b) Biological invasions as a component of South Africa’s global change research effort. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 851–874.
  84. Vimercati G, Davies SJ, Measey J (2018) Rapid adaptive response to a mediterranean environment reduces phenotypic mismatch in a recent amphibian invader. J Exp Biol 221:p.jeb174797CrossRefGoogle Scholar
  85. Vavilov NI (1926) Studies on the origin of cultivated plants. Bull Appl Bot Genet Plant Breed 16:1–248Google Scholar
  86. Visser V, Langdon B, Pauchard A, Richardson DM (2014) Unlocking the potential of Google Earth as a tool in invasion science. Biol Invasions 16:513–534. CrossRefGoogle Scholar
  87. Wilson EO (2016) Half-Earth: our planet’s fight for life. Liveright Publishing Corporation, a division of W. W. Norton, New YorkGoogle Scholar
  88. Wilson JRU, Dormontt EE, Prentis PJ, Lowe AJ, Richardson DM (2009) Something in the way you move: dispersal pathways affect invasion success. Trends Ecol Evolut 24:136–144. CrossRefGoogle Scholar
  89. Wilson JRU, Ivey P, Manyama P, Nänni I (2013) A new national unit for invasive species detection, assessment and eradication planning. S Afr J Sci 109:Art. #0111, 0113 pp.
  90. Wilson JRU et al (2016) Biological invasions and natural colonisations are different—the need for invasion science. Neobiota 31:87–98. CrossRefGoogle Scholar
  91. Wilson JR, Panetta FD, Lindgren C (2017) Detecting and responding to alien plant incursions. Ecology, biodiversity, and conservation. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  92. Wilson JRU et al (2018) Indicators for monitoring biological invasions at a national level. J Appl Ecol 55:2612–2620. CrossRefGoogle Scholar
  93. Wilson JR et al (2020) The role of environmental factors in promoting and limiting biological invasions in South Africa. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 353–384.
  94. Wingfield MJ, Brockerhoff EG, Wingfield BD, Slippers B (2015) Planted forest health: the need for a global strategy. Science 349:832–836. CrossRefPubMedGoogle Scholar
  95. Wood AR (2017) Fungi and invasions in South Africa. Bothalia: Afr Biodivers Conserv 47:a2121. CrossRefGoogle Scholar
  96. Zengeya TA, Kumschick S, Weyl OLF, van Wilgen BW (2020) An evaluation of the impacts of alien species on biodiversity in South Africa using different assessment methods. In: van Wilgen BW, Measey J, Richardson DM, Wilson JR, Zengeya TA (eds) Biological invasions in South Africa. Springer, Berlin, pp 487–512.

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Authors and Affiliations

  1. 1.South African National Biodiversity Institute, Kirstenbosch Research CentreCape TownSouth Africa
  2. 2.Centre for Invasion Biology, Department of Botany and ZoologyStellenbosch UniversityStellenboschSouth Africa
  3. 3.Centre for Invasion Biology, Department of Zoology and EntomologyUniversity of PretoriaPretoriaSouth Africa

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