The continuity-contiguity problem in fragmentation-biodiversity research

A primary question for researchers in the field of conservation science concerns the fragmentation of biodiversity-supporting habitat. Key debates revolve around the relevance of habitat composition and configuration for conservation outcomes. Central to this debate is the measurement and delineation of the habitat patch, which informs fragmentation-related metrics and their evaluation. Despite the need to quantify and model habitat fragmentation, the habitat patch concept itself has been subject to criticism concerning its ability to adequately reflect the heterogeneity of resource distributions in complex landscapes. In this paper, we present the continuity-contiguity problem, which is one of the fundamental challenges related to the delineation of habitat in space, and discuss its implications for fragmentation-biodiversity research. We outline the potential contribution of recent developments in spatial-ecological methods and the leveraging of uncertainty in the modelling process to address four common issues related to the habitat patch concept: the gap-crossing problem; the need for multi-variate habitat delineation; the delineation of interior-edge transitions and the need to parameterise habitat as both a discrete and continuous spatial entity. We conclude with several recommendations for studies on fragmentation-biodiversity outcomes where the continuity-contiguity problem may influence the research process.