The acceptable range of variation within the desirable stable state as a measure of restoration success

Abstract

It is standard practice to compare the status of performance indicators between restoration and reference sites to monitor restoration progress and demonstrate restoration success. However, standard methods for defining the reference ecosystem, selecting reference sites, and measuring success are surprisingly lacking. Our study develops these methods based on the acceptable range of variation (ARV) within the desirable stable (reference) state as a measure of restoration success. The method (1) constrains application to the contemporary landscape to avoid the problematic historical range of variation concept and idealized restoration targets; (2) acknowledges the theory of alternative stable states and ecosystem dynamics and posits that the reference ecosystem should be clearly defined as a desirable stable (reference) state; and (3) shows that identifying an acceptable thematic (classification) scale and an acceptable management timeframe is essential to defining the desirable stable (reference) state. We present two approaches to calculating an ARV and a simulation method to explore reference site replication sufficiency. We apply the methods to two contrasting Australian restoration case studies and recommend that routine adoption of these methods would make a significant contribution to the science and practice of restoration ecology and to the assessment of restoration success.

Setting a reference for wetland carbon: the importance of accounting for hydrology, topography, and natural variability

“…We found that SOC stocks varied substantially among neighboring least-disturbed wetlands with similar vegetation and hydrogeomorphology. In a restoration context, this implies that reference conditions have inherent uncertainty, and that success should be evaluated against the range of natural variability [105]. Although hydrologic metrics explained some variability in SOC stocks, our results highlight the complex and context-dependent relationships between wetland hydrology and ecosystem processes.…”

“…Constraints on time and funding often put these conditions out of reach for practitioners. With outcomes unpredictable, restoration assessment would benefit from a more rigorous treatment of uncertainty and a greater focus on the natural range of variability [104,105]. For example, strategies like setting targets for groups of wetlands (rather than for individual wetlands) and reducing the precision of targets acknowledge ecosystem dynamism and promote heterogeneity [106,107].…”

Epigaeic invertebrate diversity of post‐mining revegetation evaluated by comparison with adjacent remnant woodlands

“…Due to the novel or hybrid nature of rehabilitated ecosystems in the Bowen Basin, it was recommended that the evaluation of rehabilitation should be based on properties found naturally in a broad range of local vegetation types rather than a specific vegetation type (Doley & Audet 2013). Reference sites were used to define the range of variation in the invertebrate diversity levels of the target ecosystem (Oliver et al 2022), remnant woodlands, as a measure of rehabilitation success.…”

“…Typical of landforms in this region, the five reference sites were all on gentle slopes of less than 4° slope. As a negative control (Oliver et al 2022), representing the starting vegetation type (i.e., a grassland) and as a counterpoint to the developing wooded vegetation of rehabilitation (Bowie et al 2019), three grassland sites (cleared woodlands) on a similar range of soil types as the woodlands were also selected (P1 on fertile soils, P2 on clay plains and P3 on coarse‐textured soils). Typical of pastures in the Central Queensland region, grassland sites were dominated by the introduced pasture grass, Buffel Grass Cenchrus ciliaris (Eyre et al 2009).…”

“…In the Bowen Basin, the aim of most mine rehabilitation is to establish a self‐sustaining ecosystem, resembling natural habitats that were present before mining; native woodlands in this instance. Typically, reference sites comprising natural vegetation in the vicinity of the minesite are used to provide benchmarks against which the progress of the rehabilitation can be evaluated (Brady & Noske 2010; Gould 2012; Oliver et al 2022). The use of local reference sites in remnant vegetation also provides a benchmark for calibrating impacts of regional influences outside the mining footprint such as climatic drivers of ecosystem change.…”