Warming Oceans Put More Stress on Whales
Climate change is making life more difficult for whales, dolphins, and porpoises that must adapt to shrinking sea ice and decline in their prey species, according to a new study released by the Whale and Dolphin Conservation Society (WCDS) and the global conservation organization World Wildlife Fund (WWF).
“Whales in hot water?” finds that climate change impacts are greatest in the Arctic and the Antarctic, and cetaceans such as belugas, narwhals, and bowhead whales that rely on icy polar waters for habitat and food are likely to suffer most from the reduction in sea ice.
The cetaceans also must deal with changes in sea temperature and the freshening of seawater due to melting ice and increased rainfalls.
“Whales, dolphins and porpoises have some capacity to adapt to their changing environment,” said Mark Simmonds, international director of science at the WCDS. “But the climate is now changing at such a fast pace that it is unclear to what extent whales and dolphins will be able to adjust, and we believe many populations to be very vulnerable to predicted changes.”
Accelerating climate change adds to disturbances from other human activities, such as chemical and noise pollution, collisions with ships, and entanglement in fishing nets, which kills some 1,000 cetaceans every day, the conservation groups report.
The Arctic could be seasonally free of sea ice as early as the year 2020, according to a report issued in April by the National Center for Atmospheric Research and the University of Colorado’s National Snow and Ice Data Center.
As sea ice shrinks, there will be more human activities, such as commercial shipping, oil, gas, and mining exploration and development as well as military activities, in previously untouched areas of the Arctic, the conservation groups warn.
Other projected impacts of climate change listed in the report include the reduction of available habitat for several cetacean species, such as river dolphins, that are unable to move into colder waters.
Cetacean survival is also threatened by the acidification of the oceans as they absorb growing quantities of carbon dioxide, an increased susceptibility of whales, dolphins, and porpoises to diseases, and reduced reproductive success, body condition, and survival rates, the report finds.
Krill, a tiny shrimp-like marine animal that is dependent on sea ice, is the main source of food for many of the great whales, but the krill population is declining in key areas, the report finds. In the Antarctic, sea ice is decreasing in several areas, resulting in massive declines in krill which spend the winter under the ice.
In January 2006, a 30-year study published by an international team of scientists showed that El Nino ocean warming events affect the availability of krill in the Southern Ocean. This in turn affects the number of calves produced by southern right whales in the South Atlantic.
Southern right whales, Eubalaena australis, migrate from the South Atlantic to the Southern Ocean to feed. Following an El Nino event, changes in sea temperatures affect the availability of krill, which is the main diet of these whales.
The conservation groups warn that the cumulative impact of climate change on other human-induced impacts on cetaceans, such as pollution, bycatch, and overfishing, means that reducing all threats to cetaceans is now essential for their long-term survival.
The two conservation organizations are urging governments to cut global emissions of carbon dioxide by at least 50 percent by the middle of this century. The two organizations also are calling on the International Whaling Commission (IWC) to facilitate research on future impacts of climate change on cetaceans, including by supporting a special climate change workshop in the coming year.