Analysis of climate paths reveals potential limitations on species range shifts.

Forecasts of species endangerment under climate change usually ignore the processes by which species ranges shift. By analysing the 'climate paths' that range shifts might follow, and two key range-shift processes--dispersal and population persistence--we show that short-term climatic and population characteristics have dramatic effects on range-shift forecasts. By employing this approach with 15 amphibian species in the western USA, we make unexpected predictions. First, inter-decadal variability in climate change can prevent range shifts by causing gaps in climate paths, even in the absence of geographic barriers. Second, the hitherto unappreciated trait of persistence during unfavourable climatic conditions is critical to species range shifts. Third, climatic fluctuations and low persistence could lead to endangerment even if the future potential range size is large. These considerations may render habitat corridors ineffectual for some species, and conservationists may need to consider managed relocation and augmentation of in situ populations.