Survival rates of both young and older animals are nega-
tively affected during years with little sea ice in western
Hudson Bay in Canada
84
. Additional analyses of climate
variability in the past across broader parts of the polar
bears’ range strengthen the case for pessimism regard-
ing the future of polar bears
70,85
.
The current situation of polar bears in Hudson Bay, along
with the uncertainty regarding their future across the Arc-
tic, led the IUCN (International Union for the Conserva-
tion of Nature) Polar Bear Expert Group to suggest upgrad-
ing the status of polar bears on the IUCN Red List from
“Least Concern” to “Vulnerable”
86
. This has increased
pressure to place the polar bear on the United States list
of threatened species under the Endangered Species Act.
Statements suggesting that the polar bear likely faces glo-
bal extinction in the wild by the end of this century as a
result of global warming are becoming commonplace
87
.
Ivory gull.
While the timing or certainty of extinction is difficult to
Photo: Georg Bangjord
predict – it is clear that polar bears are “on thin ice”.
Whales this hypothesis. Whether these species could live in an
In the Arctic a small number of whale species have also Arctic with no summer sea ice is uncertain. At very least
become sea-ice specialists. Bowhead whales, white (bel- they would face increased competition from temperate
uga) whales and narwhals have all “lost” their dorsal fins whale species that would expand their ranges northward,
as an adaptation to ice-living, and live in tight associa- as well as increased predation risk
31,64
.
tion with sea ice through much of the year.
Seabirds
The actual linkages that bind these species to sea ice are The abundance and distribution of many seabirds spe-
not completely understood, because all three species do cies in polar regions are related to sea ice distribution,
spend time in ice-free waters. One commonly-cited sug- particularly to the location of ice edges. Some of the larg-
gestion for the attractiveness of ice to these whales is the est seabird colonies in the world occur in the Arctic and
avoidance of killer whale (Orca) predation
88
, but the extent Antarctic
91,92
and changes in sea-ice cover are likely to
of their movements into sea-ice areas appears to be exces- impact seabirds indirectly through changes in prey avail-
sive for what would be needed to avoid killer whales
89
and ability
93
. Seabirds, because they respond to anything that
actually can expose them to predation by polar bears
90
as affects food availability, are good indicators of a system’s
well as increase the risk of entrapment in the ice. Thus, productivity
94
. Although seabirds are quite mobile com-
it seems likely that food availability and lack of competi- pared to other organisms, changes in the spatial and
tion from other whale species in ice-filled waters is also temporal availability of food can have dramatic effects
a major attractant, although few data are available to test on their reproduction and survival
95
.
86 GLOBAL OUTLOOK FOR ICE AND SNOW