cooperation and support from all stakeholders—those who support the use of these
species and those who support their control.
Cities are “surrogates for global change” (Lahr et al. 2018) and we need to further
our understanding of invasion in urban areas. Although urban ecosystems are
hotspots for biological invasions, invasion science has given scant attention to
exploring the invasion dynamics and the challenges facing managers in towns and
cities, particularly in developing countries (Gaertner et al. 2017a). This is also the
case in South Africa which has a long history of managing biological invasions in
natural and semi-natural ecosystems (Macdonald et al. 1986a; van Wilgen 2020,
Chap. 2). This chapter reviews the emerging knowledge of patterns and processes,
impacts, perceptions and management of biological invasions in urban ecosystems in
South Africa.
11.2 Patterns and Processes
Urban ecosystems are those where humans live at high densities and where the built
infrastructure covers a large proportion of the land surface (Pickett et al. 2001).
Following the South African settlement typology (van Huyssteen et al. 2015), this
chapter focuses primarily on towns and cities, but examples are also drawn from
smaller human settlements such as staff and tourist villages in protected areas
(Foxcroft et al. 2008) and military bases surrounded by natural vegetation (e.g.
Milton et al. 2007).
Alien species are abundant in all cities, but the understanding of invasion
dynamics (i.e. the factors that mediate the introduction, establishment, proliferation
and spread of alien species) in urban ecosystems is generally poor worldwide
(Gaertner et al. 2017b). In South Africa, knowledge of the patterns and processes
of invasions in urban settings is poor despite a long history of alien species
introductions into urban centres across the country. Urban areas throughout
South Africa, like those worldwide, share certain features that facilitate the proliferation of some alien species. These attributes exist irrespective of the biome in which
the town or city occurs. While there is some “overflow” of natural-area invaders into
urban settings (e.g. Australian wattles in Cape Town; Chromolaena odorata, Triffid
Weed, in Durban), urban areas in South Africa share a similar set of invasive species
from all taxonomic groups with many cities around the world, e.g. Ailanthus
altissima (Tree of Heaven), Rattus rattus (Black Rat). For these species, general
features common to urban environments, rather than biome-specific factors, are the
dominant drivers of invasions. However, South Africa’s unique history has had a
major imprint on the composition of alien species pools in urban areas, the ways in
which alien and invasive species are perceived, their impact on ES and human wellbeing, and on approaches to management.
A wave of alien species introductions followed the colonisation of South Africa
by Europeans from the mid-seventeenth century (van Wilgen et al. 2020, Chap. 1).
From this time, distinct phases of introductions driven by the needs and activities of
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species and those who support their control.
Cities are “surrogates for global change” (Lahr et al. 2018) and we need to further
our understanding of invasion in urban areas. Although urban ecosystems are
hotspots for biological invasions, invasion science has given scant attention to
exploring the invasion dynamics and the challenges facing managers in towns and
cities, particularly in developing countries (Gaertner et al. 2017a). This is also the
case in South Africa which has a long history of managing biological invasions in
natural and semi-natural ecosystems (Macdonald et al. 1986a; van Wilgen 2020,
Chap. 2). This chapter reviews the emerging knowledge of patterns and processes,
impacts, perceptions and management of biological invasions in urban ecosystems in
South Africa.
11.2 Patterns and Processes
Urban ecosystems are those where humans live at high densities and where the built
infrastructure covers a large proportion of the land surface (Pickett et al. 2001).
Following the South African settlement typology (van Huyssteen et al. 2015), this
chapter focuses primarily on towns and cities, but examples are also drawn from
smaller human settlements such as staff and tourist villages in protected areas
(Foxcroft et al. 2008) and military bases surrounded by natural vegetation (e.g.
Milton et al. 2007).
Alien species are abundant in all cities, but the understanding of invasion
dynamics (i.e. the factors that mediate the introduction, establishment, proliferation
and spread of alien species) in urban ecosystems is generally poor worldwide
(Gaertner et al. 2017b). In South Africa, knowledge of the patterns and processes
of invasions in urban settings is poor despite a long history of alien species
introductions into urban centres across the country. Urban areas throughout
South Africa, like those worldwide, share certain features that facilitate the proliferation of some alien species. These attributes exist irrespective of the biome in which
the town or city occurs. While there is some “overflow” of natural-area invaders into
urban settings (e.g. Australian wattles in Cape Town; Chromolaena odorata, Triffid
Weed, in Durban), urban areas in South Africa share a similar set of invasive species
from all taxonomic groups with many cities around the world, e.g. Ailanthus
altissima (Tree of Heaven), Rattus rattus (Black Rat). For these species, general
features common to urban environments, rather than biome-specific factors, are the
dominant drivers of invasions. However, South Africa’s unique history has had a
major imprint on the composition of alien species pools in urban areas, the ways in
which alien and invasive species are perceived, their impact on ES and human wellbeing, and on approaches to management.
A wave of alien species introductions followed the colonisation of South Africa
by Europeans from the mid-seventeenth century (van Wilgen et al. 2020, Chap. 1).
From this time, distinct phases of introductions driven by the needs and activities of
278
L. J. Potgieter et al.