From geographic coverage to climatic representativeness: protected areas, environmental fragmentation, and species risk under climate change

Conservation assessments usually evaluate protected areas and species risk in geographic space, yet biodiversity is also structured by the availability and spatial configuration of environmental conditions. This study uses environmental space as a broad-grain diagnostic framework to ask whether terrestrial protected areas represent climatic regimes in proportion to global prevalence, whether threatened vertebrates occupy the same climatic regions as overall richness, and how future climates reorganize the prevalence and fragmentation of present-day regimes. Environmental fragmentation quantifies the spatial disaggregation of geographically separated places sharing similar climates, not local habitat fragmentation. Present-day climate, protected areas and range maps for 32,570 amphibian, bird, mammal and squamate species, including 6252 threatened species, were projected into univariate gradients and multivariate climate space. Protected areas were not a proportional sample of terrestrial climate: precipitation and water-balance gradients, including annual potential evapotranspiration, precipitation of the driest month and annual precipitation, were broadly underrepresented. Threatened richness was strongly correlated with total richness, but maxima were displaced along several gradients and in multivariate climate space, identifying regimes where threatened species were elevated relative to the total-richness background. Species-level exposure to environmental fragmentation differed among taxa and depended on environmental representation after accounting for range size and phylogeny. Future projections showed substantial climate-space prevalence redistribution, especially under SSP5–8.5, but no uniform increase in climatic fragmentation. These results show that climatic representativeness, threat concentration and future exposure can be evaluated within a common environmental-space framework, complementing geographic conservation planning while remaining distinct from fine-scale protected-area or population assessments.