Effects of climate change on marine mammals

With increasing global ocean temperature, increasing sea level, and increasing ocean acidification, the effects of climate change on marine mammals will likely be greatest on ice-associated species inhabiting polar regions, species reliant on upwelling boundary currents, species of restricted geographic range, and those species reliant on low-lying islands, atolls and coral reef habitats. Direct effects include the loss of sea-ice as a substrate for polar bears, ice seals and walrus, loss of breeding habitat for pinnipeds due to sea level rise, loss of coral reef habitat due to ocean warming and acidification, loss of seagrass habitat due to severe weather events, and changes in seasonal residency for migratory species due to changes in sea-ice extent and availability of open water in polar regions. Indirect effects include changes in pathogens and the frequency of epizootics linked to warming ocean conditions, and altered community structure and function. A lack of synchrony between the timing of migrations, seasonal ocean production, and prey availability is an important driver of climate impacts on marine mammals. Though some long-term, multi-decadal time series of marine mammal populations exist, with which to evaluate the impacts of climate change, more are needed. Risk assessment models are needed on regionally-specific scales, to aid policy development and management because of the need to minimize the synergistic effects of climate change and anthropogenic stresses to marine mammal populations.