Whales Set To Chase Shrinking Feed Zones

A new report* summarises WWF research showing 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.

“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 Dr Susan Lieberman, Director of WWF International's Species Programme and head of the WWF delegation to the IWC meeting.

Migratory whales meanwhile may need to travel 200-500 kilometres further south to find the “frontal” zones which are their crucial foraging areas. Migratory whale species which will be affected include 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, mainly during the first half of the 20th century.

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 areas.

“The impact on whales is one more imperative for the world to take decisive action to reduce the risk of catastrophic climate change,” Dr Lieberman said. “However, the IWC must also take the opportunity of this southern hemisphere 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.”

WWF is recommending the protection of critical habitats and for also limiting other non-climate stresses to whale populations such as fishing, pollution and ocean noise.

*Reference: Ice breaker: Pushing the boundaries for whales summarises research commissioned by WWF from scientists Dr. Cynthia Tynan and Dr. Joellen Russell which was presented to the IWC Scientific Committee in the following paper: Tynan, C. T. and Russell, J.L. 2008. Assessing the impacts of future 2°C global warming on Southern Ocean cetaceans.

Background

• Current projections have 2°C of average global warming over pre-industrial levels – widely regarded as a threshold level for unacceptable risks of runaway climate change – arriving on average in 2042, with impacts going furthest and fastest in polar regions.
• Warming of 2°C will reduce winter sea-ice coverage by 10-15 per cent overall and up to 30 percent in some key areas.
• Shrinking ice covered areas affect krill production in two ways –sea ice is a refuge for krill larvae in winter, and an area of intense algal blooms in summer on which the krill feed. Krill is so fundamental to the Southern Ocean ecosystem that the impacts will not be confined to whales but also to seals, seabirds and penguins, and to fisheries productivity.
• “Frontal zones” are where water masses of different temperatures meet. They are associated with upwelling of nutrients supporting large plankton populations on which species such as Antarctic krill feed.