Marine Mammals

What is already happening?
  • The main effects of climate change on marine mammals are range shifts, loss of habitat, food-web changes, increased exposure to algal toxins and susceptibility to disease. 
  • Warm-water species, such as striped dolphin, short-beaked common dolphin, and Cuvier’s beaked whale are moving northwards and the ranges of cold-water species, such as white-beaked dolphin, are contracting.

Medium evidence, medium agreement

Over the last two decades, the evidence for range shifts in a number of cetacean species (e.g. short-beaked common dolphin, striped dolphin, Atlantic white-sided dolphin, white-beaked dolphin), reported previously has strengthened

What could happen in the future?
  • Continued increases in sea temperature could result in a shift in the composition of cetacean species, with an increased presence of warm-water species. 
  • The main influences of climate change on marine mammals are likely to be indirect via changes in prey distribution and availability, resulting in range shifts in some regional populations. 
  • Marine mammal species that make long-distance seasonal migrations (e.g. most baleen whales) will likely arrive earlier or remain in high latitudes for longer, increasing breeding opportunities.

Low evidence, medium agreement

Regarding predictions for the future, there is general consensus that the effects currently observed will continue although how those effects are mediated for different species remains poorly understood.

Key Challenges and Emerging Issues
  • Establishing long term monitoring of distribution and abundance change of cetacean species to assess impacts of climate change.
  • Quantifying the synergistic effects of climate change and other human stressors on cetacean range shifts.
  • Distinguishing climate effects from other drivers in recent observed changes in seal populations.
  • Understanding how direct impacts on lower trophic levels affect top predators through improved links to upper trophic levels in ecosystem models.