Here we describe the contexts for ecological restoration following alien plant
invasions, summarise theoretical and applied research, and outline South Africa’s
contributions to this field. Conceptual frameworks such as the “restorative continuum” (McDonald et al. 2016a, b) are useful in addressing ecological restoration
requirements along a gradient of habitat change or degradation, and for visualising
desired outcomes. Restorative interventions may be seen as a continuum from the
bare minimum of reducing the causes of degradation in permanently modified
habitats, to restoring to an appropriate natural reference ecosystem (McDonald
et al. 2016a, b). When the potential for recovery (or progress to some desired
state) is determined to have been compromised by invasive alien species, active
restoration by manipulating the abiotic and biotic ecosystem components may be
required to achieve goals. In contrast, removal of the invasion-mediated impact
through appropriate control measures alone may be sufficient for ecosystems
deemed to have good recovery potential. In practice, the latter generally refers to
invaded ecosystems with intact native seed banks and/or surviving remnant native
plant populations. Here we illustrate some outcomes of spontaneous regeneration
and active restoration applications using South African case studies.
23.2 Global and National Contexts
23.2.1 The Need for Ecological Restoration
Restoration ecology is a relatively new science that gained prominence in the 1980s,
and has since expanded in response to the human-induced, rapid rate of habitat
transformation and degradation across the globe (Hobbs and Richardson 2011).
Global land modification and degradation estimates range from 0.99–6 billion ha
(up to 66% of global land surface) and the annual, economic costs arising from these
impacts are estimated to be ~ 10–17% of current global Gross Domestic Product
(GDP) (Crossman et al. 2017). Various international instruments, to which
South Africa is a signatory, seek to reverse this degradation, including the
Bonn Challenge and Sustainable Development Goal 15 (Mohieldin and Caballero
2015) and the Convention on Biological Diversity Aichi Targets (2010). Within
South Africa, the National Biodiversity Framework (Government Gazette
No. 32474, 2009) summarises the actions required to conserve and restore the
country’s natural ecosystems.
23.2.2 Restoration Ecology
Empirical research in restoration ecology has promoted a deeper understanding of
ecosystem structure and functioning (Pretorius et al. 2008; Gaertner et al. 2011;
Zaloumis and Bond 2011). This has led to the development of conceptual models
that link agents of change and ecosystem responses to potential restoration actions
23 Biological Invasions and Ecological Restoration in South Africa
667
invasions, summarise theoretical and applied research, and outline South Africa’s
contributions to this field. Conceptual frameworks such as the “restorative continuum” (McDonald et al. 2016a, b) are useful in addressing ecological restoration
requirements along a gradient of habitat change or degradation, and for visualising
desired outcomes. Restorative interventions may be seen as a continuum from the
bare minimum of reducing the causes of degradation in permanently modified
habitats, to restoring to an appropriate natural reference ecosystem (McDonald
et al. 2016a, b). When the potential for recovery (or progress to some desired
state) is determined to have been compromised by invasive alien species, active
restoration by manipulating the abiotic and biotic ecosystem components may be
required to achieve goals. In contrast, removal of the invasion-mediated impact
through appropriate control measures alone may be sufficient for ecosystems
deemed to have good recovery potential. In practice, the latter generally refers to
invaded ecosystems with intact native seed banks and/or surviving remnant native
plant populations. Here we illustrate some outcomes of spontaneous regeneration
and active restoration applications using South African case studies.
23.2 Global and National Contexts
23.2.1 The Need for Ecological Restoration
Restoration ecology is a relatively new science that gained prominence in the 1980s,
and has since expanded in response to the human-induced, rapid rate of habitat
transformation and degradation across the globe (Hobbs and Richardson 2011).
Global land modification and degradation estimates range from 0.99–6 billion ha
(up to 66% of global land surface) and the annual, economic costs arising from these
impacts are estimated to be ~ 10–17% of current global Gross Domestic Product
(GDP) (Crossman et al. 2017). Various international instruments, to which
South Africa is a signatory, seek to reverse this degradation, including the
Bonn Challenge and Sustainable Development Goal 15 (Mohieldin and Caballero
2015) and the Convention on Biological Diversity Aichi Targets (2010). Within
South Africa, the National Biodiversity Framework (Government Gazette
No. 32474, 2009) summarises the actions required to conserve and restore the
country’s natural ecosystems.
23.2.2 Restoration Ecology
Empirical research in restoration ecology has promoted a deeper understanding of
ecosystem structure and functioning (Pretorius et al. 2008; Gaertner et al. 2011;
Zaloumis and Bond 2011). This has led to the development of conceptual models
that link agents of change and ecosystem responses to potential restoration actions
23 Biological Invasions and Ecological Restoration in South Africa
667