Box 2 Identifying the appropriate ecological restoration approach

Correctly assessing the capacity of various parts of a site to naturally regenerate, with or without assistance, aids the selection of appropriate approaches and treatments, avoiding costly errors and increase the likelihood of attaining similarity between the restoration outcome and the appropriately identified reference ecosystem.

Regeneration potential can be hidden in dormant in-situ propagules or nearby sources. A useful initial rule of thumb is to undertake skilled assessment of the site and its surrounds to identify any scope for harnessing this potential through one of the regeneration approaches described in this box. Reintroductions of species (or reinforcements of populations) should only be carried out if and when potential for regeneration has been tested or is known to be not possible or sufficient (Figure 2).

Four approaches are typically applied, informed by ecological ground-based site assessment to determine level of in-situ resilience and colonisation potential (Figure 3, Table 1). All will require ongoing adaptive management until recovery is secured. A mosaic of approaches is common where there is a diversity of different conditions across a site. That is, some parts of a site may require one of the natural regeneration approaches, while others require a combined regeneration/reintroduction or a reconstruction approach.

1. Spontaneous regeneration. Pre-existing biota are very often able to recover unaided after cessation of recent or relatively low levels of predation or competition from invasive species and cessation of degrading practices such as native vegetation clearing, overgrazing, over-harvesting, over-fishing, restriction of water flows or inappropriate fire regimes. Animal species may be able to migrate back to the site if connectivity is in place, while plant species may recover through resprouting or germination from remnant soil seed banks or seeds that naturally disperse from nearby sites. Examples of spontaneous regeneration.


2. Facilitated regeneration (In Australia and elsewhere this is often referred to as 'assisted regeneration'). Where the removal of causes of degradation is insufficient to allow spontaneous regeneration, active interventions can often foster natural regeneration from in-situ propagules (e.g. soil seed banks or buds) or from recolonisation. Examples of lower-level abiotic interventions include removing competition from invasive species, reinstating environmental flows and fish passage (in aquatic sites), and (in terrestrial sites) applying disturbances such as fire to break seed dormancy, or installing habitat features such as hollow logs, rocks, woody debris piles and perch trees to attract fauna. Higher level abiotic interventions include remediating contamination or substrate chemistry, reshaping substrates, watercourses and landforms, and building habitat features such as shell reefs. Examples of facilitated regeneration.


3. Combined regeneration/reintroduction. Varying responses by individual species to the same impact type can cause some plant or animal species drop out of an ecosystem earlier than others. This is often reflected in one or other vegetation stratum or faunal trophic level being impacted more than others, resulting in variable recovery. In such cases, after addressing the causal factors, and fostering as much natural regeneration as possible, the less resilient plants and/or animals may require reintroduction. This approach can also be appropriate where existing populations of plants and/or animals are low and supplementary genetic reintroductions may be needed (reinforcement). Care should be taken to ensure that decisions to reintroduce or reinforce are strictly evidence-based. Example of Combined regeneration/reintroduction.
4. Reconstruction Where damage is very high, not only will all causes of degradation need to be addressed, and abiotic damage corrected, but also all (or at least a high proportion) of a site’s desirable biota will need to be reintroduced using current best practice methods. Works required to prepare substrates prior to reintroductions may be nil, low or high depending on the extent of damage at the site. As recovery after reconstruction commences, regeneration approaches can be applied superimposed, further improving outcomes. Examples of reconstruction.