Abstract
Understanding the effects of natural environmental variation on biodiversity can help predict response to future anthropogenic change. Here we analyse a large, long‐term data set of sightings of deep‐water cetaceans from the Atlantic, Pacific and Indian Oceans. Seasonal and geographic changes in the diversity of these genera are well predicted by a convex function of sea‐surface temperature peaking at c . 21 °C. Thus, diversity is highest at intermediate latitudes – an emerging general pattern for the pelagic ocean. When applied to a range of Intergovernmental Panel on Climate Change global change scenarios, the predicted response is a decline of cetacean diversity across the tropics and increases at higher latitudes. This suggests that deep‐water oceanic communities that dominate > 60% of the planet’s surface may reorganize in response to ocean warming, with low‐latitude losses of diversity and resilience.