Few if any parts of the world are experiencing the impacts of climate change to the extent of the Arctic. But teasing out the precise effects of that change on the region's wildlife isn't always straightforward.
For some species, notably polar bears, the basic math isn't difficult: Polar bears need sea ice, and as that sea ice declines so most likely will they. Although even here, there is nuance: whereas populations in the southern Beaufort Sea and western Hudson Bay have experienced declines in numbers and body conditions there is some evidence that bears in the Chukchi Sea region are faring comparatively well. For other species, the picture is murkier.
In a landmark 2008 overview of the likely impacts of climate change on Arctic marine mammals, Sue Moore and Henry Huntington classified resident Arctic species into two groups: ice-obligate and ice-associated. The four species in the former group - polar bears, walruses, ringed seals and bearded seals - could be expected to be most clearly and directly affected by ice declines.
But among the responses of ice-associated species, they wrote, "there will likely be surprises." For example, for bowhead whales - which are found only in Arctic seas - "reductions in sea ice may actually enhance feeding opportunities."
Eight years on, there's some evidence this prediction is proving accurate, as Matthew Berger notes in a blog post for Nautilus. Berger quotes Moore, a NOAA biologist, as saying that, "At least for now, it's a very good time to be a bowhead whale. In terms of resiliency, bowheads could be near the top because they're already built to survive in tough conditions."
Moore cites as supporting evidence a 2015 study that found the body condition of bowheads hunted by Alaskan Eskimos to actually be improving, and Berger notes separate research that suggests habitats will "generally become more suitable for bowheads both earlier and later in the year in the Beaufort Sea, due to increases in the availability of krill and copepods, a group of microscopic crustacean."
Here, too, however, there are caveats, in that what may be true for bowheads in the Beaufort Sea region may not hold for those off northeastern Canada and western Greenland. There, warming waters may see an increase in Atlantic copepods at the expense of the larger and thus more calorie-rich Arctic ones - although it's possible that a greater abundance overall will counteract any declines in food quality.
As Berger observes: "There are a lot of unknowns when an ice-adapted world suddenly loses its ice."