An equitable method for evaluating habitat amount and potential occupancy

Abstract

Landscape connectivity measures based on metapopulation theory were developed over 20 years ago. Initially, they applied classic metapopulation models to simple patch-based representations of landscapes using vector spatial data structures. Realism was improved by developing dynamic estimates of occupancy and metapopulation capacity, the latter providing a measure of the integrated habitat amount. Such measures are used to estimate the ability of habitat networks to support metapopulation persistence. The original methods for occupancy mapping and metapopulation capacity were adapted to work with fine-grained, continuous-value raster data. That step shifted the method outside of the classic metapopulation model which left some methodological issues unresolved; in particular, what has been termed the deceptive paradox of patch-based connectivity whereby perverse and what we describe as inequitable results are obtained through arbitrary circumscription of the analysis grid and through the trading of habitat between habitat quality, extent and connectivity. We provide a solution to this issue and apply it within the frame of Drielsma and Ferrier's (2009) raster-based Rapid Evaluation of Metapopulation Persistence (REMP).We demonstrate our solution using simple hypothetical examples; and in order to demonstrate the practicality of our approach to real-world settings, we apply the approach to habitat suitability mapping of the White-browed Treecreeper (Climacteris affinis) in south eastern New South Wales, Australia.