Experts outline primary risks of climate change to natives of the Arctic
loss of sea ice due to climate change could spell disaster for polar
bears and other Arctic marine mammals. The April Special Issue of
Ecological Applications examines such potential effects, puts them in
historical context, and describes possible conservation measures to
mitigate them. The assessment reflects the latest thinking of experts
representing multiple scientific disciplines.
Sea ice is the common habitat feature uniting these unique and diverse
Arctic inhabitants. Sea ice serves as a platform for resting and
reproduction, influences the distribution of food sources, and provides
a refuge from predators. The loss of sea ice poses a particularly
severe threat to Arctic species, such as the hooded seal, whose natural
history is closely tied to, and depends on, sea ice.
undergoes dramatic seasonal transformation. Arctic marine mammals
appear to be well adapted to the extremes and variability of this
environment, having survived past periods of extended warming and
"However, the rate and scale of current climate change
are expected to distinguish current circumstances from those of the
past several millennia. These new conditions present unique challenges
to the well-being of Arctic marine mammals," says Sue Moore
(NOAA/Alaska Fisheries Science Center).
Climate change will pose
a variety of threats to marine mammals. For some, such as polar bears,
it is likely to reduce the availability of their prey, requiring them
to seek alternate food. Authors Bodil Bluhm and Rolf Gradinger
(University of Alaska, Fairbanks) note that while some Arctic marine
mammal species may be capable of adjusting to changing food
availability, others may be handicapped by their very specific food
requirements and hunting techniques. Species such as the walrus and
polar bear fall under this category, while the beluga whale and bearded
seal are among those who are more opportunistic in their eating habits
and therefore potentially less vulnerable, at least in this regard.
a quantitative index of species sensitivity to climate change, Kristin
Laidre (University of Washington) and colleagues found that the most
sensitive Arctic marine mammals appear to be the hooded seal, polar
bear, and the narwhal, primarily due to their reliance on sea ice and
Shifts in the prey base of Arctic marine
mammals would likely lead to changes in body condition and potentially
affect the immune system of marine mammals, according to Kathy Burek
(Alaska Veterinary Pathology Services). She and fellow researchers
point out that climate change may alter pathogen transmission and
exposure to infectious diseases, possibly lowering the health of marine
mammals and, in the worst case, their survival. Changing environmental
conditions, including more frequent bouts of severe weather and rising
air and water temperatures, also could impact the health of Arctic
The effects of climate change will be compounded
by a host of secondary factors. The loss of ice will open the Arctic to
new levels of shipping, oil and gas exploration and drilling, fishing,
hunting, tourism, and coastal development. These, in turn, will add new
threats to marine mammal populations, including ship strikes,
contaminants, and competition for prey.
Timothy Ragen (US Marine
Mammal Commission) and colleagues describe how conservation measures
may be able to address the secondary effects of climate change, but
that only reductions in greenhouse gas emissions can-over the
long-term-conserve Arctic marine mammals and the Arctic ecosystems on
which they depend.
Ecological Society of America. April 2008.