populations reside in cities. The trend of rapid urbanisation in developing countries
(UNFPA 2007), and the ever-increasing dependence on the provision of ES, means
that growing negative impacts on these services is a rising concern for city managers
(Potgieter et al. 2017). While urban ecosystems provide multiple ES for human wellbeing, they can also generate functions, processes and attributes that result in
perceived or actual negative impacts on ES and human well-being—these are termed
ecosystem disservices (EDS) (Shackleton et al. 2016; Vaz et al. 2017). Invasive
animals in urban landscapes have been linked with the spread of human disease,
reduction in local biodiversity, and damage to property and infrastructure (Shochat
et al. 2010; Reis et al. 2008). Urban plant invasions have been implicated in human
health issues, increased fire hazard, and safety and security risks (Pyšek and Richardson 2010; van Wilgen and Richardson 2012; Potgieter et al. 2018, 2019a, b).
Management of invasive species in cities differs markedly in different parts of the
world. This is often closely linked to the availability of funding and the approaches
for setting priorities for city planning. Some cities prioritise urban green space, while
others channel limited funding earmarked for “environmental issues” to other
priorities more closely aligned with socio-political imperatives (Irlich et al. 2017).
City-based managers of invasive species are typically aligned to environmental or
biodiversity protection mandates. This means that, although control of invasive
species may be undertaken to comply with national legislation, the decisions that
are made, and plans that are implemented are often aimed at alleviating pressures on,
or at reversing damage to, natural ecosystems and biodiversity. Such concerns are
typically highly context-specific (e.g. Potgieter et al. 2018).
Urban environments have complex land-tenure patterns, with smaller and more
numerous land parcels and consequently many more landowners (e.g. privatelyowned property, national and provincial government land, municipal property managed by different departments). This pattern complicates the coordination of management activities (Gaston et al. 2013). Large numbers of landowners mean a
diversity of incentives, policies, and practices for managing invasive species, and a
strong likelihood of conflicts of interests (Dickie et al. 2014; van Wilgen and
Richardson 2014; Gaertner et al. 2016; Zengeya et al. 2017). Species that provide
both ES and EDS generate conflicts around their use and management. Invasive
species may provide provisioning ES (e.g. firewood), but at the expense of biodiversity, leading to conflicts over which should be prioritised (van Wilgen 2012).
Indeed, management to optimise specific ES exclusively may exacerbate associated
EDS, and interventions aiming at reducing EDS only may also reduce ES (Shackleton et al. 2016). Site accessibility also presents a considerable challenge in
controlling alien plant invasions in the urban landscape.
Although most research on biological invasions has focussed on ecological
aspects (García-Llorente et al. 2008; Hui and Richardson 2017), the ways in
which social dimensions mediate responses to invasions are emerging as crucial
considerations in invasion science (Kull et al. 2011, 2018; Shackleton et al. 2019b).
Effective engagement with stakeholders is emerging as a crucial ingredient in
invasive species management (Novoa et al. 2018; Shackleton et al. 2019a). Sustainable strategies for dealing with conflict-generating invasive species rely on
11 Biological Invasions in South Africa’s Urban Ecosystems
277
(UNFPA 2007), and the ever-increasing dependence on the provision of ES, means
that growing negative impacts on these services is a rising concern for city managers
(Potgieter et al. 2017). While urban ecosystems provide multiple ES for human wellbeing, they can also generate functions, processes and attributes that result in
perceived or actual negative impacts on ES and human well-being—these are termed
ecosystem disservices (EDS) (Shackleton et al. 2016; Vaz et al. 2017). Invasive
animals in urban landscapes have been linked with the spread of human disease,
reduction in local biodiversity, and damage to property and infrastructure (Shochat
et al. 2010; Reis et al. 2008). Urban plant invasions have been implicated in human
health issues, increased fire hazard, and safety and security risks (Pyšek and Richardson 2010; van Wilgen and Richardson 2012; Potgieter et al. 2018, 2019a, b).
Management of invasive species in cities differs markedly in different parts of the
world. This is often closely linked to the availability of funding and the approaches
for setting priorities for city planning. Some cities prioritise urban green space, while
others channel limited funding earmarked for “environmental issues” to other
priorities more closely aligned with socio-political imperatives (Irlich et al. 2017).
City-based managers of invasive species are typically aligned to environmental or
biodiversity protection mandates. This means that, although control of invasive
species may be undertaken to comply with national legislation, the decisions that
are made, and plans that are implemented are often aimed at alleviating pressures on,
or at reversing damage to, natural ecosystems and biodiversity. Such concerns are
typically highly context-specific (e.g. Potgieter et al. 2018).
Urban environments have complex land-tenure patterns, with smaller and more
numerous land parcels and consequently many more landowners (e.g. privatelyowned property, national and provincial government land, municipal property managed by different departments). This pattern complicates the coordination of management activities (Gaston et al. 2013). Large numbers of landowners mean a
diversity of incentives, policies, and practices for managing invasive species, and a
strong likelihood of conflicts of interests (Dickie et al. 2014; van Wilgen and
Richardson 2014; Gaertner et al. 2016; Zengeya et al. 2017). Species that provide
both ES and EDS generate conflicts around their use and management. Invasive
species may provide provisioning ES (e.g. firewood), but at the expense of biodiversity, leading to conflicts over which should be prioritised (van Wilgen 2012).
Indeed, management to optimise specific ES exclusively may exacerbate associated
EDS, and interventions aiming at reducing EDS only may also reduce ES (Shackleton et al. 2016). Site accessibility also presents a considerable challenge in
controlling alien plant invasions in the urban landscape.
Although most research on biological invasions has focussed on ecological
aspects (García-Llorente et al. 2008; Hui and Richardson 2017), the ways in
which social dimensions mediate responses to invasions are emerging as crucial
considerations in invasion science (Kull et al. 2011, 2018; Shackleton et al. 2019b).
Effective engagement with stakeholders is emerging as a crucial ingredient in
invasive species management (Novoa et al. 2018; Shackleton et al. 2019a). Sustainable strategies for dealing with conflict-generating invasive species rely on
11 Biological Invasions in South Africa’s Urban Ecosystems
277