Using landscape fragmentation thresholds to determine ecological process targets in systematic conservation plans

Systematic conservation planning requires that quantitative targets be set for both biodiversity pattern and processes. While the challenge of setting quantitative representation targets has been well addressed in the literature, guidelines for conceptualising and setting process targets are lacking. Process targets can be defined as the minimum amount of natural habitat that must remain to ensure the long-term survival of the majority of species. While a representation target may represent the majority of species in a landscape, this target often falls far short of conserving processes necessary for the persistence of these species. This paper explores the potential for landscape ecology research to provide useful insights into developing process targets by relating critical thresholds in habitat amount to the probability of population persistence. It is proposed that these thresholds provide a basis for developing generic top-down ecological process targets in conservation planning. The percolation threshold, theoretically defined at 59%, is increasingly used to inform research into ecological state shifts and ecosystem resilience. This threshold may provide a basis for developing top-down process targets in instances where comprehensive bottom-up spatial data on individual ecological processes is unavailable. In the context of ongoing global habitat loss, this approach provides a pragmatic, but also potentially biologically meaningful, way of incorporating defensible and quantitative ecological process targets or biodiversity persistence goals into conservation plans.