Minimising re-invasion is an important restoration objective and may require
manipulation of both the biotic and abiotic components of the degraded ecosystem.
Actively re-establishing canopy cover of native species may also be required to
suppress the weedy, light-requiring secondary invader species (Falk et al. 2013;
Herron et al. 2013).
The third degradation threshold may be reached at a later stage of invasion and
results from positive biotic-abiotic feedback loops, whereby the persisting alien
invader entrenches the changes in ecological processes that in turn further promote
the invader above native species (Gaertner et al. 2014; Vilà et al. 2011; Suding et al.
2004). Examples of where the invader disproportionately benefits, ultimately
resulting in the third degradation threshold being reached and preventing the
re-establishment of native species, includes altered nutrient-cycling patterns
(Gaertner et al. 2012b) and altered fire regimes resulting from increased biomass
and/or changed fuel distribution (D’Antonio and Vitousek 1992). Once the third
degradation threshold is reached, ecological restoration may be very difficult and
expensive; in such cases less ambitious goals, such as rehabilitation, may be more
realistic.
23.4 Best Practice: Restoration Planning
Whatever the context for an ecological restoration project, good planning and
stakeholder involvement are essential if restoration goals are to be achieved. Following the four principles outlined by Suding et al. (2015), planned restoration
projects strive to increase ecological integrity, i.e. either through alien control and
spontaneous regeneration, or through additional interventions in tandem with alien
control. Secondly, restoration is best planned for long-term sustainability. For
example, practitioners can ensure that sufficient resources are available for followup alien control, monitoring and native propagule re-introduction if required, before
embarking on initial control of the alien. The altered state of the ecosystem must be
thoroughly assessed to ascertain whether restoration is likely to result in a sustainable, positive change. This would also assist in assessing priorities and setting
realistic goals (D’Antonio and Meyerson 2002). Thirdly, most projects have goals
based on a historically-informed reference ecosystem (Aronson et al. 2017). Nevertheless, it is also recommended to consider the future, and whether landscape-scale
or global changes and external factors such as public perception could thwart desired
restoration goals. Fourthly, restoration interventions should benefit and engage
society.
Restoration planning should involve invasion and restoration ecologists, practitioners and other stakeholders who jointly develop restoration goals that are ecologically and economically feasible (Gaertner et al. 2012a). A participatory scenario
approach for planning, implementing and monitoring restoration is one such inclusive approach (Metzger et al. 2017). At this stage, research questions may be
addressed to fill knowledge gaps and data collected to better inform restoration
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P. M. Holmes et al.
manipulation of both the biotic and abiotic components of the degraded ecosystem.
Actively re-establishing canopy cover of native species may also be required to
suppress the weedy, light-requiring secondary invader species (Falk et al. 2013;
Herron et al. 2013).
The third degradation threshold may be reached at a later stage of invasion and
results from positive biotic-abiotic feedback loops, whereby the persisting alien
invader entrenches the changes in ecological processes that in turn further promote
the invader above native species (Gaertner et al. 2014; Vilà et al. 2011; Suding et al.
2004). Examples of where the invader disproportionately benefits, ultimately
resulting in the third degradation threshold being reached and preventing the
re-establishment of native species, includes altered nutrient-cycling patterns
(Gaertner et al. 2012b) and altered fire regimes resulting from increased biomass
and/or changed fuel distribution (D’Antonio and Vitousek 1992). Once the third
degradation threshold is reached, ecological restoration may be very difficult and
expensive; in such cases less ambitious goals, such as rehabilitation, may be more
realistic.
23.4 Best Practice: Restoration Planning
Whatever the context for an ecological restoration project, good planning and
stakeholder involvement are essential if restoration goals are to be achieved. Following the four principles outlined by Suding et al. (2015), planned restoration
projects strive to increase ecological integrity, i.e. either through alien control and
spontaneous regeneration, or through additional interventions in tandem with alien
control. Secondly, restoration is best planned for long-term sustainability. For
example, practitioners can ensure that sufficient resources are available for followup alien control, monitoring and native propagule re-introduction if required, before
embarking on initial control of the alien. The altered state of the ecosystem must be
thoroughly assessed to ascertain whether restoration is likely to result in a sustainable, positive change. This would also assist in assessing priorities and setting
realistic goals (D’Antonio and Meyerson 2002). Thirdly, most projects have goals
based on a historically-informed reference ecosystem (Aronson et al. 2017). Nevertheless, it is also recommended to consider the future, and whether landscape-scale
or global changes and external factors such as public perception could thwart desired
restoration goals. Fourthly, restoration interventions should benefit and engage
society.
Restoration planning should involve invasion and restoration ecologists, practitioners and other stakeholders who jointly develop restoration goals that are ecologically and economically feasible (Gaertner et al. 2012a). A participatory scenario
approach for planning, implementing and monitoring restoration is one such inclusive approach (Metzger et al. 2017). At this stage, research questions may be
addressed to fill knowledge gaps and data collected to better inform restoration
674
P. M. Holmes et al.