Articles > Whales Set To Chase Shrinking Feed Zones

Whales Set To Chase Shrinking Feed Zones

July 1, 2008 — Endangered
migratory whales will be faced with shrinking crucial Antarctic
foraging zones which will contain less food and will be further away, a
new analysis of the impacts of climate change on Southern Ocean whales
has found.

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.

Source : World Wildlife Fund

 


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