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

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.