Measuring, Reporting, and Verification of Forest Restoration

The baseline is key to understanding the capacity of the site to achieve desirable outcomes and an appropriate reference ecosystem. A reference ecosystem represents a non-degraded version of the site, complete with its flora, fauna, and other biota, abiotic elements, functions, processes, and successional states that might have existed had degradation not occurred (Gann et al. 2019). Reference sites may be rare in regions that have few protected areas, and agencies need to be aware that assumptions in their selection may imply lower standards than would have been considered historically (i.e. referred to as shifting baselines). Based on information from multiple reference sites, a reference model predicts the expected ecosystem condition that the restoration site could achieve in the future, adjusted to accommodate changed or predicted environmental conditions. 

Typically, the first condition restoration funding requires stakeholders to demonstrate is that the intervention has changed the measure of the ecosystem such that it is appreciably different to locations where the management interventions did not take place. Evidence actions have moved outcomes beyond the range of business-as-usual scenarios is the minimum standard necessary for any project to be deemed successful and the criteria that qualifies projects to claim additionality. If this is not the case and the site is still similar to unrestored sites, then either this indicator is not an effective measure of the kinds of change brought by the restoration, or it is too soon for a project to claim successful impact for that particular indicator. We refer to the expected values of an indicator in a standard, un-restored, system as the counterfactual model. 

If additionality has been achieved, then the second condition for describing the quality of restoration success is based on its similarity to states describes by the reference model. Ecosystems naturally display variation, and recovery following restoration does not follow a precise orderly process, and therefore the expectations of both the counterfactual and reference models will include a range of values that reflect the observed variation in measured outcomes. 

As stated, restoration objectives should be explicit, measurable and time limited. For this reason, restoration objectives should be selected from among properties that can be reliably observed and modelled at reference ecosystems. However, many ecosystems, not just forests, may take a long time to fully recover and the rate at which particular properties will approach the reference state is not necessarily linear. Therefore, within SUPERB we adopted a broader view of reference states to include sites that had been recovering for different periods of time in order to characterise the trajectory of succession, and the condition a project should have achieved after a given timeframe.

Projects should therefore claim they have achieved additional ecological outcomes only when it is highly unlikely indicator values fall within the range of expectations for a counterfactual, and should only claim they have successfully delivered restoration outcomes when the indicators confidently fall within the range of the reference model. While forest restoration may take many forms, additionality for some indicators will in practice be a trivial exercise. For example, afforestation projects that aim to diversity tree species will immediately have had an impact beyond the expectations of traditional monoculture forestry if multiple species are  planted. However, to be considered high quality, the diversity of trees that persist and grow would be expected to continue to match that of other similar restoration projects. Ecosystem restoration cannot be defined by a single variable, and therefore it is important to recognise that multiple indicators will be required to ensure success is robustly defined. A project may therefore achieve rapid success for some indicators that diverge quickly (Fig. 1 Indicator A), and simultaneously still within the range of counterfactual conditions for other indicators that diverge later as the habitat matures (Fig. 1 Indicator B).

 

Figure 1. The success of a restoration project can be defined by how indicators of biodiversity or ecosystem services compare to two models, the counterfactual (purple), and the Reference Model (green). The models define the range of expected values for that indicator under business-as-usual or restoration scenarios respectively. As an illustration, consider the range of indicator values derived from project monitoring over time. At time t1 and t2, monitoring outcomes overlapped with the counterfactual, and additionality could not be confirmed. At time t3, additionality was confirmed for Indicator A, but not B. At time t4, monitoring suggested the project may be within the expected range of successful Reference projects for indicator A, but there was a possibility Indicator B was still within the range of the counterfactual. By time t5, both Indicator A and B are within the range of successful Reference projects, indicating both additionality and successful achievement of expected outcomes.