Three kinds of whale, six varieties of seal, the walrus and the polar bear all have these five things in common: they are marine mammals; they depend on the Arctic for their survival as species; they are vulnerable; and biologists know surprisingly little about them.

 

And since the Arctic is warming twice as fast as the rest of the planet, their future could become even more threatened as climate change increases habitat loss.

 

The stress, so far, is on the word 'could', as the first challenge is to establish the facts.

 

A global study team led by Kristin Laidre, principal scientist at the University of Washington Polar Science Centre in Seattle, reports in the journal Conservation Biology that marine mammals are "disproportionately threatened and data poor compared with their terrestrial counterparts."

 

The narwhal, beluga and bowhead whales, the ringed, bearded, spotted, ribbon, harp and hooded seals, the walrus, and the polar bear are "particularly vulnerable due to their dependence on sea ice."

 

All these animals make their living on the ice and in waters north of the Arctic Circle, and all are important predators. They are also important to indigenous and settler peoples in the frozen North as many can be legally harvested, and others are iconic tourist attractions. Either way, they help communities survive.

 

So the researchers set out on what they believe is the first comprehensive global review of what is known about the populations of these animals, and about the way their local habitats may be changing.

 

The study divided the Arctic into 12 regions and began to look at population numbers and trends, and the local pattern of seasonal change in the ice.

 

They identified 78 distinct populations of the 11 species, and began to assemble estimates of numbers. These range from millions for the ringed seals to a few hundred for the beluga whales of Ungava Bay in the Canadian Arctic.