Identifying and testing conservation decision thresholds in temperate montane grasslands

Abstract

Conservation decision thresholds have most often been described within the context of triggering management actions necessary to maintain an ecological system within a desired state. Thresholds are also applied within conservation legislation, often as triggers to determine when certain regulations may or may not apply. In many applications, thresholds have been criticized for being subjective, inconsistent and open to bias and rather than being derived from sound and objective analysis of ecological data they can result from undocumented judgement and opinion. Although judgement and opinion may be necessary for setting decision thresholds in circumstances where appropriate data are lacking, a failure to use structured processes for obtaining, analysing and presenting these can result in contentious, unsubstantiated thresholds. This paper demonstrates how thresholds for identifying grassland conservation values, for the purposes of decision making under vegetation clearing legislation, can be estimated from simple floristic indicators after combining the judgment of multiple experts through hierarchical modelling. Using two stages of elicitation and modelling, the resulting conservation value states were found to be consistent and predictable, correlated with known paddock-level disturbance history and congruent with prior condition states that define an endangered grassland ecosystem. While the thresholds, and the underpinning coefficients, may not reflect the opinion of all grassland ecologists, they are transparent, testable and can be updated or modified to incorporate additional criteria and a greater diversity of stakeholders. The approach could be adopted to similar contexts in other vegetation types where policy or regulatory decision triggers are required.