Using indices of species’ potential range to inform conservation status

Assessments of conservation status are typically based on short-term extinction risk, but the value indicators that compare current state species (e.g., abundance or distribution) to potential baselines is increasingly recognised. The use in legislation hindered by ambiguity how should be determined and interpreted, leading inconsistent application. Here, we explored species’ ranges as a consistent means quantifying for assessing distributions, key component status. Using breeding birds Great Britain (GB) case study, simulated where bird would expected occur today modelled world without human land use. We calculated indices contrasted these human-free with realised ranges. Our analyses revealed 42% GB have wider than 28% narrower These could lead reassessments priorities. Eighteen assigned ‘least concern’ regional IUCN Red List had much ranges, suggesting their more degraded currently recognised criteria. Some not under active management candidates higher prioritisation. approach provides systematic range reliant variable historic data expert opinion and, thereby, step forward resolving major contemporary problem assessment: set consistently. insights produced also scientific cultural relevance, revealing likely exist absence impacts. This used identify areas targeted restoration actions might return historically extirpated species, even novel colonists.