A biogeographic model of thermal habitat loss during global temperature change

Global warming has been implicated as a trigger of mass extinctions in the past. Although species track their thermal niches as isotherms move poleward, systematic changes in the area of habitable space (i.e., their thermal habitat) are expected to influence their extinction risk. Quantifying thermal habitat changes is difficult in the geological past, where information about geography and the distributions of species are highly incomplete. We therefore present a formalized model of thermal habitat change, resulting from the interaction of spherical geometry, thermal niche preference, latitudinal temperature profile, and global temperature change. Our results suggest an overall decrease in available thermal habitat during global warming. Thermal habitat is lost primarily from lower latitude and polar areas, whereas temperate areas are less affected. Although patterns of extinction are ultimately dependent on the geography of available habitat space, the extent to which species occupy their thermal niches, additional abiotic parameters, and biotic interactions, our simple theoretical model provides the basic expectation for spatial patterns of habitat loss, and therefore potentially species loss, during global warming.