A young polar bear comes to shore during the summer in northern Alaska. (Photograph by Eric Regehr, U.S. Fish and Wildlife Service)

Despite Arctic marine mammals being icons of climate change, little is known about their populations across the Arctic. In a first ever global review of Arctic marine mammals, published last week in Conservation Biology, an international team of scientists provides a circumpolar range assessment. They studied population status and trends for 11 species, including polar bears, ice seals, narwhals, and walruses.

The scientists also measured changes in sea ice habitat and recommended conservation priorities for the future. National Geographic spoke with lead author Kristin Laidre of the University of Washington’s Polar Science Center about the team’s findings.

Why is it so difficult to get data for Arctic marine mammals?

The Arctic is inherently a difficult place to work. You’re dealing with extreme weather conditions that make operations challenging. It’s also very expensive, and Arctic surveys require enormous resources. For many of these species, their populations have never been surveyed.

Arctic marine mammals are also wide-ranging. They move over hundreds of square kilometers and across international borders. This makes surveys difficult and requires time, resources, and often international collaboration.

What trends did you find in sea ice habitat loss?

The timing of sea ice formation is critical for most species because their life events, like feeding and reproduction, are timed with specific weeks of the year when there is sea ice present. We conducted an analysis to examine changes in the timing of the spring sea ice break-up and the fall sea ice freeze-up. This estimated the total number of weeks of the summer—low ice—season, during which the ice is relatively open. In almost all areas, the duration of the summer season has increased by five to ten weeks since satellites started recording data in 1979.

Different populations of Arctic marine mammals are responding differently to climate change. Why?

There’s strong evidence that the ice-dependent Arctic marine mammals like polar bears, ice seals, and walruses will not do well over the long-term given projections for an ice-free Arctic. These species require ice for many different life functions. In the case of the ice-associated species like cetaceans—narwhals, beluga whales, and bowhead whales—we are less certain.

There is currently variability in how species and populations are responding to sea ice loss, including the ice-dependent species. In the Chukchi Sea between Siberia and Alaska, for example, polar bears are in just as good or better condition as they were several decades ago, despite the fact that sea ice has been lost. That’s in contrast to polar bears in the neighboring southern Beaufort Sea.

Another example of variability is bowhead whales. In northern Alaska, bowhead whale body condition has improved over the past several decades of sea ice loss. Declining sea ice opens up new habitat for these whales, and also extends their production period. In this case, ice loss has actually been positive.

So in some areas populations are doing well right now, and in other areas they’re not. This is important to recognize. Over the long-term, we’ll likely see negative trends for the ice-dependent species.

Were there any surprises while doing this research?

The surprises came when we were looking at the sea ice changes; they are just so dramatic. We know that the Arctic is losing ice, but when we quantify the changes with this approach we get at what matters for Arctic marine mammals.

Forecasts of sea ice loss for unabated emissions versus aggressive greenhouse gas mitigation do not substantially diverge for 20 to 25 years into the future. So that means we can expect these habitat changes to continue to occur and have to be prepared to face the challenges ahead.

You highlight the complex relationship between Arctic marine mammal conservation efforts and the animals’ use as renewable resources in some communities. Can you explain that relationship?

We found that 78 percent of Arctic marine mammals are legally hunted for subsistence. In the modern world, it’s really rare to have large wild mammals support the nutritional and cultural well-being of communities the way these species do in the Arctic. That’s something very important that needs to be considered in conservation activities. There needs to be a good dialogue between local communities, scientists, and managers.

The best way to do that is through what we call co-management, which is federal and state partners working together with indigenous governments and communities to ensure the best management and conservation of these species.

What are your recommendations for the future?

Accurate scientific data—currently lacking for many species—will be key to making informed and efficient decisions about conservation challenges and tradeoffs in the 21st century. There is a need for overall improved monitoring of these species by developing circumpolar monitoring plans that allow scientists to work together across Arctic nations.

And there should be a better focus on quantifying the impacts of industrial activities. We know very little about the cumulative impacts of these activities.

These species are increasingly going to be listed under international and national frameworks for protected species legislation because they’re at risk from climate change. However, that kind of legislation isn’t getting at the main driver of habitat loss, which is the need to reduce emissions of greenhouse gases over the long-term. That’s a real global challenge that needs to be addressed.