Principle 4 The goal of ecological restoration is full recovery, insofar as possible, even if outcomes take long timeframes or involve high inputs.

Qualification of a project as an ecological restoration activity is not determined by the duration of the project but by the intent to achieve the highest and best level of recovery possible. It is important to bear in mind that the desired outcome may take long timeframes. This can be because sufficient time has not yet elapsed for recovery processes to run their course; sufficient restoration resources or knowledge are not yet available to overcome recovery barriers; or mitigating impacts originating from outside the site require lengthy negotiation. While success can be achieved ultimately by continuous improvement over time in many cases (e.g. non-mandatory cases), the achievement of full recovery would require more substantial human and financial investment including indepth research where only relatively short timeframes are available (e.g. many mandatory restoration cases).

To help managers track progress towards project goals over time, the Standards offer a tool (five-levels or ‘stars’) for progressively assessing and ranking degree of recovery over time. This tool is summarised in Tables 2 and 3 and more fully described, relative to the six attributes of ecological restoration, in Table 4. The recovery wheel diagram is provided in Figure 5.

Five-star recovery—that is, where the ecosystem is on a self-organising trajectory to full recovery based on an appropriate local native reference ecosystem—is the standard to which ecological restoration projects ideally aim. However, in some cases, constraints may limit potential to less than full level of recovery. Such cases can still be referred to as ecological restoration projects as long as the aim is for substantial recovery relative to the appropriate local native reference ecosystem. However, projects that aim for low levels of recovery—or solely recovery of ecosystem functions without including the appropriate local biota—are better referred to as rehabilitation (Appendix 1).

Table 2 Description of the key ecosystem attributes used to characterize the reference ecosystem, as well as to evaluate baseline condition, set project goals, and monitor degree of recovery at a restoration site (adapted from Gann et al. 2019)

Attribute	Description
Absence of threats	Direct degradation drivers (e.g. overutilization, contamination inputs, sources of invasive species) are minimal or effectively absent.
Physical conditions	Environmental conditions (including the physical and chemical conditions of soil, water, and topography) required to sustain the ecosystem are present.
Species composition	The native species characteristic of the appropriate ecosystem are present, whereas invasive species are minimal or effectively absent.
Structural diversity	Appropriate diversity of key structural components, including demographic stages, faunal trophic levels, vegetation strata, and spatial diversity are present.
Ecosystem function	Appropriate levels of growth and productivity, nutrient cycling, decomposition, habitat, species interactions, and types and rates of disturbance are present.
External exchanges	The ecosystem is appropriately integrated into its larger landscape or aquatic context through positive abiotic and biotic flows and exchanges.

Table 3 Summary of generic standards for one to five star recovery levels. Note 1: Each level is cumulative. Note 2: The different attributes will progress at different rates—see Table 2 that shows more detailed generic standards for each of the six attributes.

Number of stars	Summary of recovery outcome
1	Over-utilization ceased and conservation status secured but other threats persisting at high level. Substrates physically and chemically showing some similarity to the reference ecosystem and low level of native biota present. Foundational level of ecosystem processes, functions and exchanges present.
2	Some remaining threats still high in degree. Physical conditions capable of supporting some biota. Site has a small subset of characteristic native species with intermediate levels of undesirable species present. Positive exchanges with surrounding environment initiated.
3	Low numbers of threats but still intermediate in degree. An intermediate subset of characteristic native species is established and are likely to be self-sustaining due to presence of intermediate levels of functions and processes. Positive exchanges with surrounding environment in place for many species and processes.
4	Threats low in number and degree and physical conditions of high similarity to reference. A substantial subset of characteristic biota present (representing all species groupings), along with characteristic structure, and evidence of key functions and processes capable of supporting self-sustaining populations. There are positive exchanges with other native ecosystems in the surrounding environment.
5	Threats effectively absent. A characteristic assemblage of biota present, exhibiting structural and trophic complexity of very high similarity to the reference ecosystem. Self-organizing potential on a trajectory likely to emulate the reference ecosystem functions and processes and are likely to be sustained. Appropriate cross-boundary flows are enabled, and resilience is restored with return of appropriate disturbance regimes.

Figure 5 Progress evaluation ‘recovery wheel’. This template allows a manager to illustrate the degree to which the project is achieving its ecosystem goals over time. In this hypothetical case, a one-year-old reconstruction site is on its way to a four-star condition. (Blank templates for the diagram and its accompanying proforma are available in Appendix 5.)

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Notes for interpreting the five-star evaluation system

1. The five-star system has been designed to evaluate the progression of an ecosystem along its recovery trajectory. It is not a tool for evaluating the practitioner or record of actions undertaken.


2. The five-star system represents a conceptual gradient, providing a framework that can be interpreted by managers, practitioners and regulators in more quantitative terms to suit a specific ecosystem. The sub-attribute labels in the wheel should be seen as a guide and can be amended if necessary. The indicators or metrics used to specifically describe and interpret recovery at each ranking level for a specific ecosystem need to be interpreted for each project. These should be identified at the outset of a project to provide ecologically meaningful information about project goals.


3. Evaluation can only be as rigorous (and therefore as reliable) as the monitoring that informs it. As some projects can only provide informal monitoring, evaluation needs to transparently specify the level of detail and degree of formality of the monitoring from which the conclusions have been drawn. This means that the recovery wheel or an evaluation table cannot be used as evidence of restoration success without the monitoring report on which it is based.


4. Each restoration project does not necessarily start at a one-star ranking. Sites that involve remnant biota and unaltered substrates will start at a higher ranking—while sites where substrates are impaired and/or biota are absent will start at a lower ranking. Whatever the entry point of a project, the aim will be to progress the ecosystem along the trajectory of recovery towards a five-star rated recovery. recovery.


5. Although the ideal aim is to achieve a five-star rating for all attributes in a restored system, full recovery of some attributes will be difficult to achieve at larger scales. Complete removal of external threats in a fragmented landscape or aquatic environment, for example, is usually beyond the scope of site-specific restoration project but reduction of these threats may be possible (e.g. pollution regulation, ‘no take’ zoning, installation of nutrient filters, ongoing control of pest species etc). Assessment of ongoing threat levels should be in place at the restoration site. If removal or reduction of external threats is not fully achievable, monitoring and reporting needs to indicate whether this is the result of external constraints and to what extent these are resolvable.


6. Evaluation using the five-star system and and wheel must be site- and scale-specific. An evaluation will provide more detail when applied at the scale of an individual project or site. However multiple evaluations can be aggregated to inform degree of recovery in larger programs. Where larger scale projects retain substantial areas of permanently converted industrial activity or urban development, scores will necessarily be lower. Nonetheless, in such situations additional detail in supplementary reporting can capture even low level gains at larger scales where these are important for some species or ecological processes. Similarly, in social-ecological systems, progress with important social outcomes of the project (such as increasing level of capacity and stewardship commitment by stakeholders) can be reported separately to capture social elements.

Table 4 Sample one to five star recovery scale interpreted in the context of the six key ecosystem attributes used to measure progress along a trajectory of recovery. This five-star scale represents a gradient from very low to very high similarity to the reference model and is applicable to any level of recovery where a reference ecosystem is used. As it is a generic framework, users must develop indicators and monitoring metrics specific to the ecosystem and sub-attributes they identify. (Note: The starting point of an attribute can be zero or any star level and examples in the table accumulate along the spectrum.) (Adapted from Gann et al. 2019)

Attribute	One-star	Two-star	Three-star	Four-star	Five-star
Absence of threats	Some direct degradation drivers (e.g. over-harvesting, overgrazing, active contamination) absent and conservation status secured, but others remain high in number and degree.	Direct degradation drivers (including, e.g. sources of invasive species, absence of appropriate natural disturbances) intermediate in number and degree.	Number of direct degradation drivers low but some may remain intermediate in degree.	Direct degradation drivers, both external and onsite, low in number and degree.	Threats from direct degradation drivers minimal or effectively absent.
Physical conditions	Most physical and chemical properties of the site’s substrates and hydrology (e.g. soil structure, nutrients, pH, salinity, hydrological conditions) still highly dissimilar to reference ecosystem but some showing improved similarity.	Physical and chemical properties of substrates and hydrology, remain at low similarity levels relative to reference ecosystem but capable of supporting some biota of reference ecosystem.	Physical and chemical properties of substrates and hydrology stabilized within intermediate range of reference ecosystem and capable of supporting growth and development of many characteristic native biota.	Physical and chemical conditions of substrates and hydrology within high range of reference ecosystem and suitable for ongoing growth and recruitment of most characteristic native biota.	Physical and chemical conditions of substrates and hydrology highly similar to that of the reference ecosystem with evidence they can indefinitely sustain all characteristic species and processes.
Species composition	Some colonizing native species present (e.g. ~2% of the reference ecosystem). Very high levels of non-native invasive or undesirable species.	A small subset of characteristic native species present (e.g. ~10% of the reference ecosystem) across site. High to moderate levels of non-native invasive or undesirable species.	A subset of key native species present	Substantial diversity of characteristic biota (e.g. up to 60% of reference) present on the site and representing a wide diversity of species groups. No inhibition by undesirable species	High diversity of characteristic species (e.g. > 80% of reference) across the site, with high similarity to the reference ecosystem; improved potential for colonisation of more species over time
Structural diversity	One horizontal stratum of the reference present but spatial patterning and community trophic complexity still largely dissimilar to reference ecosystem.	More than one stratum of the reference present but some similarity of spatial patterning and trophic complexity, relative to reference ecosystem.	Most strata of the reference present and intermediate similarity of spatial patterning and trophic complexity relative to reference ecosystem.	All strata of the reference present and substantial similarity of spatial patterning and trophic complexity relative to reference ecosystem.	All strata present and spatial patterning and trophic complexity high. Further complexity and spatial patterning able to self-organize to highly resemble the reference ecosystem.
Ecosystem function	Processes and functions (e.g. water and nutrient cycling, habitat provision, appropriate disturbance regimes and resilience) are at a very foundational stage only, compared to the reference ecosystem.	Low numbers and levels of physical and biological processes and functions, relative to the reference ecosystem (including growth, decomposition, soil processes), are present	Intermediate numbers and levels of physical and biological processes and functions, relative the reference ecosystem (including reproduction and dispersal) are present.	Substantial levels of physical and biological processes and functions, relative to the reference ecosystem (including return of appropriate disturbance regimes) are present.	All functions and processes (including appropriate disturbance regimes) are on a secure trajectory towards the levels of the reference ecosystem and are showing evidence of being sustained.
External exchanges	Positive exchanges and flows with surrounding environment (e.g. of species, genes, water, fire) in place for only very low numbers of species and processes.	Positive exchanges with surrounding environment in place for a few characteristic species and processes.	Positive exchanges between site and surrounding environment in place for intermediate levels of characteristic species and processes.	Positive exchanges with surrounding environment in place for most characteristic species and processes and likely to be sustained.	Evidence that exchanges with the surrounding environment are highly similar to the reference ecosystem for all species and processes and likely to be sustained.