There are those who retire, and there are those who say they’re retired but still hold an adjunct professorship at the University of Alberta; serve as an emeritus scientist at Environment Canada; and win awards for their 50-plus years of research on polar bears, seals, sea ice, and climate change. Ian Stirling received the Weston Family Prize for lifetime achievement in Northern research during the annual general meeting of ArcticNet, a forum of Arctic researchers, in Vancouver this past December. The timing was poignant: that same week, more than 50,000 delegates were gathered in Paris for climate talks that aimed to establish a commitment to limit the global temperature rise to fewer than two degrees Celsius above pre-industrial levels. We spoke to Stirling about what climate change is doing to polar bear populations, where polar bear research is headed, and how to save the Arctic’s iconic animal.
Can you give us a glimpse of what it’s like in the field, observing polar bears? I was watching a female polar bear sneaking up on a seal on the summer sea ice. In the summer there are these water channels and they’re like little maps: if you look at them from the air, they’re like looking at tributaries in a braided stream where the water runs back and forth. The bear had walked along and it saw the seal, and when they’re hunting like that, they absolutely freeze. They memorize the route of where they’re going to go if they have to sneak up. This bear went into one of the water channels, so her head and eyes were right down at the water level, and she couldn’t actually see the seal, but she knew where she wanted to go. She was maybe a couple hundred metres away from the beginning when she went up this channel, and there was a fork, and she started up the right hand fork, and suddenly she realized this wasn’t gonna take her to where she wanted to go. And she didn’t lift up her head and look around; she just slowly backed up and then went into the correct fork and got herself within charging distance. I thought she really deserved to catch that seal, but she didn’t. But the fact that she knew exactly where she was, she had it all mapped out, and then knew that she had made a mistake and didn’t have to look, to me that just blew my mind as to how smart those animals are.
You’ve said before that half the number of polar bears today will still be around in 2050. Can you elaborate on that prediction? The whole concept is basically quite simple, and that is that polar bears need sea ice for a platform to hunt seals, and as the climate is warming, the ice is melting earlier and freezing up later in several parts of the Arctic that we’ve been able to document. Already it’s very clear that the times that they’re able to feed—particularly in the most important times in the late spring and early summer—are getting shorter and shorter. And the result of that is that bears are losing body condition, and as they continue to lose body condition, the females are lighter, they’re having fewer cubs, and the cubs are not surviving as well. This is not in all areas, but it is in western Hudson Bay, and we’re seeing serious effects in the Beaufort Sea.
We have lost on average about half the sea ice that we had in 1979, which is the first year that satellite coverage of the Arctic was taken. Places like Hudson Bay are breaking up three weeks earlier than they used to and freezing up a couple weeks later. We’re going to have even more significant effects over a much wider area in the Arctic. We’re likely to lose another 30 or 40 percent, or even half of the bears that we have today in the middle of the century, and unchecked, we will likely have very few bears left at the turn of the next century. In 2100, we’ll probably just have a few small remaining pockets in the northern Canadian Arctic islands and northern Greenland.
I know that it’s a very hurtful thing to think, but I’m afraid that the evidence that’s there doesn’t suggest that polar bears are going to do very well if the climate continues to warm.
What does a one-week difference in ice break-up or freeze-up mean to a polar bear? The important time for feeding for polar bears in most areas is the late spring and early summer, prior to break-up of the sea ice. That’s because ringed seal pups are born in early April. By the time the pups are weaned, about six weeks later around mid-May, most become independent of their mothers. Up to about 50 percent of their body weight at that point is fat, and they aren’t experienced with predators, which probably makes them easier to catch. Normally, they are vulnerable to predation until the ice breaks up a month or two later in early summer. After break-up, all ringed seals remain in the open water where the bears can’t catch them until the ice refreezes in the fall, once again providing a platform for the bears to hunt them from. Most bears probably take on about two-thirds or so of the fat they will need to live on through the entire year during the late spring period. Your average bear is going to need 40 or more ringed seals a year. If break-up is a week earlier than normal, it means a significant number of days of hunting at the most important period of time are gone, and the amount of fat the bear is capable of accumulating is reduced. In western Hudson Bay, where break-up is now three weeks earlier than it was 30 years ago, it’s pretty significant.
We’ve seen how the adult pregnant females, when they’re coming ashore in western Hudson Bay, they used to be an average of 280 to 290 kilograms. Now they’re down in the vicinity of 230 or 240 kilograms, so that’s a loss of an average weight of 50 or more kilograms. That’s well over 100 pounds of fat that they’re not storing anymore. We still see females with little cubs, but you see very few females with yearlings, and what that tells you is very few of those cubs are living through the first year of their life.
Is any of this loss preventable? I think quite a lot of it is, but it’s going to require the world as a whole. If we could have a magic button and turn our CO2 emissions levels back to 1990 overnight, there’s so much CO2 in the atmosphere now that it would be 20, 30, 40 years before we would see major changes. We’re stuck with a very large amount of climate warming that is already built into the system right now.
Going forward, do you see potential for working with hunters and communities to do polar bear research, and recruiting more citizen scientists? Absolutely, and I’ve always talked to and listened to and worked with local hunters. One of the things that you can guarantee is that when they see something, it’s an accurate observation. Natural history, things like denning areas, litter sizes of cubs, when bears show up or leave in particular areas that they’re familiar with, those are reliable sources of information.
Where the difficulties come is in terms of assessing population size or whether the population is increasing or decreasing, because most hunting communities are focused on a relatively local area that they travel to, which is just a very small fraction of the overall area that any polar bear population lives in, so it’s very difficult for them to project what’s going on with the population at large. If they’re seeing more bears or they’re seeing fewer bears, or they’re skinnier or they’re fatter or anything else, those observations are really valid, and they form a really good basis in designing an experiment or study to focus on addressing a larger scale question.
Some Inuit, including hunters, insist that polar bears are more resilient than we give them credit for, and that the threats to the species are exaggerated. How would you respond to that? That’s a really sensitive question and I’m sensitive to it, because the suggestion that polar bears are in serious trouble and they will disappear from significant areas—and they already are—is a very uncomfortable thing to think about. I think it’s a hurtful thing to try and imagine, and I have a great deal of sympathy for the viewpoint.
Polar bears are really big. They’re not just big because they feel like it; they’re big because they’ve got a really rich food source. So if they can’t go out on the sea ice and catch seals, sure, they can eat some berries and some grass and some vegetation, and maybe a few goose eggs, scavenge on a dead caribou or a dead beluga whale, but that will not make up anywhere near the amount of food that’s required for any of the 19 populations of polar bears. I know that it’s a very hurtful thing to think, but I’m afraid that the evidence that’s there doesn’t suggest that polar bears are going to do very well if the climate continues to warm.
Hunters have spotted and killed grolar (a.k.a. pizzly) bears, a mix of grizzly and polar bears. Is that the future of polar bears? Not really. I think that is something that catches the imagination of the public and is quite interesting, but I don’t think we’ll see that very much. From the point of view of the survival of polar bears, I don’t think it’s very significant. It’s very interesting, and of course it’s not new—there were hybrid polar bears in Ireland 30,000 years ago.
In previous interviews you’ve mentioned the “dark period” in Canadian science, when a lot of federal scientists were muzzled. Have you seen a change in that with the new government? Oh yes, there’s been a big change. Within a couple of days of the new government assuming power and being invested, an order went out to all government departments that scientists are free to talk to the media, as they always used to be, and as they should be. One of the most important things about science overall is to educate and provide information to the public so the public can make their own decisions on the basis of factual information—not to have information limited to the public because someone doesn’t like what it’s saying. That’s just wrong. Things are different again. The last 10 years have seen a great deal of muzzling and also reduction of support to various environmental studies, but particularly those that might relate to climate warming have not done well, and I think that would be of interest to all Canadians.
On the subject of climate change, what targets should world leaders be trying to set to preserve sea ice in the Arctic—and possibly save polar bears? I’m not a modeller, so I’m quoting what the majority of modellers seem to be indicating: if we can keep climate warming to go no higher than a total of two degrees Celsius over pre-industrial levels, which is still pretty high, we can probably retain some ice in the northern part of Canada in the northern latitudes. How successful that will be remains to be seen.
[Note: By the end of the Paris climate talks, world leaders had agreed on the two degree target, with an added provision to try and limit the rise to 1.5 C—thereby mitigating some of the most severe effects of climate change.]
(This interview has been edited and condensed.)