Habitat fragmentation is one of the primary threats to biodiversity. Satellite imagery is providing increasingly detailed information on habitat distributions, yet efficient techniques for linking these data to species survival are in short supply. Starting with metapopulation theory, we compared two methods of making this link: 1) metapopulation capacity and 2) relaxation rate (the rate of loss of area from a fully-occupied range). We tested our methods on threatened and non-threatened birds from four regions around the world (the Central Sichuan mountains of China, the North Central American highlands, the East Malagasy wet forests of Madagascar and the Atlantic forest of Brazil), using satellite-based estimates of original and remaining forest habitat. We compared our results against current IUCN Red List threat classifications due to fragmented range (Criterion B).
Results/Conclusions
We found the relaxation rate method to be a more intuitive means of analysis. Our calculations correlate fairly well with the IUCN’s current listings of threat status, but include a number of outliers that may require reevaluation. For instance, in the Atlantic forest of Brazil, two Vulnerable-listed species, Amaurospiza moesta and Tangara fastuosa, showed the same relaxation rate, yet the remaining range area left to A. moesta is fifty times greater than that of T. fastuosa. Finally, we use the metrics to evaluate the impact of restoring different areas of the original range on the species as a whole.
