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Some polar bear populations are decreasing, a new analysis of Arctic mammals concludes.

Some polar bear populations are decreasing, a new analysis of Arctic mammals concludes.

Eric Regehr/USFWS

Huge data gaps cloud fate of Arctic mammals

A first-ever effort to gauge the ecological status of all 11 species of marine mammals living in the Arctic reveals a mixed picture—and a lot of missing information. Researchers found that although some populations appear to be coping with climate change, others are in decline. Overall, however, scientists found that little information is available on most of the 78 known populations.

“Unless we fill critical data gaps, this is the information we have to base management decisions on for the foreseeable future—amid increasing development pressures,” says Kristin Laidre, the study’s lead author and a marine mammal biologist at the University of Washington’s Polar Science Center in Seattle.

Laidre’s team looked at what is known about marine mammal populations that play a key role in Arctic ecosystems and human communities, focusing on polar bears, beluga whales, narwhals, bowhead whales, walrus, and six different seal species. Many of these animals are fierce predators that sit atop the food web, but Laidre’s team found that they are also important subsistence resources: Arctic people hunt nearly 80% of the studied populations for food and other uses. “In modern times, there are few other places in the world where wild top predators support humans,” Laidre notes.

Some of these populations appear to be in danger, concludes the study, published online today in Conservation Biology. Overall, eight subpopulations show signs of decline, including some groups of polar bears and seals that depend on winter ice for feeding and reproduction. Satellite data show that, between 1979 and 2013, the summer ice-free season expanded by an average of 5 to 10 weeks in 12 Arctic regions, with sea ice forming later in the fall and melting earlier in the spring. Summer is 20 weeks longer in the Barents Sea, a warming hot spot along the northern coasts of Norway and Russia. 

Ten other populations are increasing, the study found, including bowhead whales and walrus, while nine others are stable. But the researchers weren’t able to establish trends for 51 of the 78 known subpopulations.

That data gap highlights the difficult task facing governments interested in managing the Arctic ecosystem, the researchers say. Still, “pulling together this big picture is a hugely important step for management agencies,” says Rosa Meehan, a retired chief of marine mammal management for the U.S. Fish and Wildlife Service in Anchorage, Alaska, and chair of a panel that is advising the multinational Arctic Council on conservation issues. Past studies have focused on a single species, place, or industry, she notes, “but this lays everything out on the table … we can start to see overlapping patterns, which will help us identify areas at greatest risk of most extreme change.”

The study “paints a realistic picture of how complicated the management of Arctic species will be going forward,” adds Mike Runge, a research ecologist and polar bear expert with the U.S. Geological Survey’s Patuxent Wildlife Research Center in Laurel, Maryland. Until international agreements are in place to cut greenhouse gas emissions, Runge says there may be increasing conflict between conservation, economic development, and the cultural and nutritional needs of indigenous people. 

For example, narwhals in northwest Greenland have long been hunted by subsistence hunters, notes study co-author Fernando Ugarte, head of the department of birds and mammals at the Greenland Institute of Natural Resources in Nuuk. But now the whales also face climate change and noise created by oil exploration and boat traffic. And less ice may mean more encounters with their predators. “Narwhals may be able to cope with any of these factors alone, but the cumulative impact could be a problem,” he says.

Given such variation, as well as the expense and logistical challenges of conducting population surveys, indigenous communities will be important partners in developing workable conservation strategies, such as the creation of new protected areas or harvest quotas, the study suggests. But there is a “frustrating” limit to management options in the Arctic, says co-author Kit Kovacs, biodiversity research leader at the Norwegian Polar Institute in Tromsø. For example, it’s hard to move or breed some of “the biggest mammals on the planet,” she notes. “You can only mitigate other manmade stressors—like ocean noise, pollution, and hunting.” Global warming, meanwhile, is threatening to make large parts of the Arctic less icy within decades.

To help Arctic organisms cope, Norway and other nations are identifying areas where icy habitats could be protected, and constructing marine protected areas around them. And the World Wildlife Fund, a Washington, D.C.–based nongovernmental organization, is pressing for the preservation of what it calls the Last Ice Area, the few strips of northeast Canada and northern Greenland where ice may persist.

Such tasks are daunting, but Kovacs hopes the new study will help “wake up smart policymakers.”