Vanishing ice threatens future of the blue whale

Posted: 20 June 2008

New analysis on the impacts of climate change on Southern Ocean whales has found that endangered migratory whales will be faced with shrinking Antarctic foraging zones which will contain less food and will be further away.

The research shows that levels of global warming predicted over the next 40 years will lead to winter sea-ice coverage of the Southern Ocean declining by up to 30 per cent in some key areas.

Blue whale
Blue whale
Blue whales weigh between 100 and 120 tons. The primary target species of modern whaling, blue whales were reduced in all waters to very low levels until protected in the mid-1960s, but are now showing some signs of recovery. (Photo courtesy IWC)
Migratory whales meanwhile may need to travel 200-500 kilometres further south to find the "frontal" zones which are their crucial foraging areas. Among the migratory whale species affected will be the Blue Whale, earth's largest living creature, and the humpback whales which are only now coming back from the brink of extinction after populations were decimated by commercial whaling in the 20th century.

"Essentially, what we are seeing is that ice-associated whales such as the Antarctic minke whale will face dramatic changes to their habitat over little more than the lifespan of an individual whale," said Heather Sohl, species officer at WWF-UK.

Both species build up the reserves that sustain them throughout the year in the frontal zones, which host large populations of their primary food source - krill.

"As frontal zones move southward, they also move closer together, reducing the overall area of foraging habitat available," the research notes. As the krill is dependent on sea ice, less sea ice is also expected to reduce the abundance of food for whales in the feeding reas.

"The impact on whales is one more imperative for the world to take decisive action to reduce the risk of catastrophic climate change," Heather Sohl said. "However, the International Whaling Commission (IWC) must also take the opportunity of this meeting to look at every possible way to increase the resilience of whale populations to climate change.

"For Antarctica's whales, the best way to do this would be to reduce all other threats - such as the unregulated and unjustified so-called 'scientific whaling' of these species conducted by Japan."

The IWC will hold its 60th annual meeting in Santiago, Chile, 23-26 June.

'Ice breaker: Pushing the boundaries for whales' summarises research commissioned by WWF from scientists Dr. Cynthia Tynan and Dr.Joellen Russell.