SECTION 2 - Six Key Principles of Ecological Restoration Practice
Six key principles are used to provide a
framework for conceptualising, defining and measuring ecological restoration,
particularly at a time of rapid environmental change. (See also Appendix
2 Values and principles underpinning ecological restoration.)
Principle 2. Restoration inputs will be dictated by level of resilience and degradation
All species (and ecosystems) possess an evolved but
variable level of resilience: that is, a capacity to recover naturally
from external stresses or shocks as long as those stresses are similar
in type and degree to those previously experienced during the evolution
of the species. This means that where human-induced impacts are low (or
where sufficient time frames and nearby populations exist for effective
recolonization) recovery can occur without assistance, but in sites of somewhat higher impact, at least some intervention is needed to initiate recovery. Where impacts are
substantially higher or sufficient recovery time or populations are not
available, correspondingly higher levels of restoration inputs and intervention
are likely to be needed (see Figure 1 below). These
may include remediation of the physical and chemical properties of the
site, supplementing populations or reintroducing missing species or ecological
processes. At extremely damaged sites, intransigent barriers to recovery
may occur, in which case adaptive management and/or active research will
be needed to identify specific solutions for restoration.
Skilful assessment of capacity for natural recovery should be done prior
to prescribing whether regeneration-basedor reconstruction-based
approaches are needed (see Box 2: Identifying the appropriate
ecological restoration approach). This is essential to optimises success
but is also important to assist prioritisation. That is, variation in
the resilience of sites (and the higher cost of assisting recovery where
the potential is lower) highlights the strategic advantage that can be
gained by investing scarce resources into areas where resilience and potential
for connectivity is higher.
Figure 1. Conceptual model of ecosystem degradation and restoration.
(Adapted from Keenleyside et al 2012, after Whisenant 1999, and Hobbs
& Harris 2001). The troughs in the diagram represent basins of stability
in which an ecosystem can remain in a steady state prior to being shifted
by a restoration or a degradation event past a threshold (represented
by peaks in the diagram) towards a higher functioning state or a lower
[Note: Not all sites in need of physical/chemical amendment depend upon
reintroduction for the return of biota - e.g. if colonisation potential
in that ecosystem is high.]
Box 2. Identifying the appropriate
ecological restoration approach
Correctly assessing the capacity of various
parts of a site to recover facilitates the selection of appropriate
approaches and treatments - avoiding inefficient use of natural
resources or restoration inputs. A useful initial rule of thumb
is to identify any potential for harnessing the natural regeneration
capacity of a species (plants, animals and other biota) and to use
'regeneration' approaches in those areas. Introductions can then
be focused on areas (or for species) where natural or assisted recovery
is low or not possible.
Three approaches can be identified that may be used alone or combined
if appropriate. All such approaches will require ongoing adaptive management
until recovery is secured.
- Natural regeneration approach.
Where damage is relatively low, pre-existing biota should be able
to recover after cessation of the degrading practices. (Examples
of degrading practices include removal of native vegetation, over-grazing,
over-fishing, restriction of water flows or inappropriate fire
regimes etc.) Animal species may be able to migrate back to the
site if connectivity is in place. Plant species may recover through
resprouting or germination from remnant soil seed banks or seeds
that naturally disperse from nearby sites.
- Assisted regeneration approach.
Recovery at sites of intermediate (or even high) degradation need
both the removal of causes of degradation and further active interventions
to correct abiotic damage and trigger biotic recovery. (Examples
of lower level abiotic interventions include reinstating environmental
flows and fish passage, applying artificial disturbances to break
seed dormancy, or installing habitat features such as hollow logs,
rocks, woody debris piles and perch trees. Examples of higher
level abiotic interventions include remediating pollution or substrate
chemistry, reshaping watercourses and landforms, building habitat
features such as shell reefs and controlling invasive plants and
- Reconstruction approach. Where
damage is high, not only do all causes of degradation need to
be removed or reversed and all biotic and abiotic damage corrected
to suit the identified local indigenous ecosystem, but also all
or a major proportion of its desirable biota need to be reintroduced.
Examples of reconstruction.
Combined approaches are sometimes warranted.
Varying responses by individual species to the same impact type
can mean that some species drop out of an ecosystem earlier than
others. In such cases less resilient species may require reintroduction
in an area where a natural or assisted regeneration approach is
generally applicable. In addition, plant species may require reintroduction,
while all or some animal species may recover without the need for
reintroduction (or vice versa). Reintroductions of plants or animals
may also be justified where genetic diversity requires supplementation.
Examples of fauna reintroduction.
A mosaic of approaches can be warranted where there is a diversity
of different condition across a site. That is, some parts of a site
may require a natural regeneration approach, while others require
an assisted regeneration or reconstruction approach, or combinations
Responding to site conditions in this way will ensure optimal levels
of similarity between the restoration outcome and conditions observed
in the appropriately identified reference ecosystem.