Global climate change, range changes and potential implications for the conservation of marine cetaceans: a review and synthesis

Global climate change has already resulted in an increase in oceanic water temperatures in some areas and is predicted to lead to further increases throughout much of the world in the foreseeable future. One possible response of cetacean species to these increases in water temperature is that species' ranges may change. Here, I provide a framework for assessing which cetacean species' ranges are likely to change as a result of increases in water temperature and whether they will expand, shift poleward or contract based on their current distributions. Based on this framework, it is predicted that the ranges of 88% of cetaceans may be affected by changes in water temperature resulting from global climate change. For 47% of species, these changes are anticipated to have unfavourable implications for their conservation, and for 21% the changes may put at least one geographically isolated population of the species at high risk of extinction. This framework suggests that certain characteristics put some species at greater risk from such changes than others. These include a range that is restricted to non-tropical waters (including temperate species) and a preference for shelf waters. These characteristics are shared by most porpoises and Lagenorhynchus species and by all members of the genus Cephalorhynchus. As a result, species in these taxa are potentially at particular risk from changes in range in response to increasing water temperatures. However, further research is required to assess whether these predictions are, indeed, correct.