A group of polar bears in south-east Greenland have adapted to hunt via blocks of freshwater ice from glaciers when sea ice retreats in the warmer months. This suggests the animals may be more resilient to climate change than we thought, although loss of sea ice remains the greatest threat to their survival.

Polar bears often hunt seals by waiting near holes in blocks of floating ice where their prey come up to breathe. Seals are also slower on ice than in water, giving polar bears an advantage. But this is being threatened by climate change and the resulting sea ice loss. As a result, the animals are projected to decline by 30 per cent over the next three polar bear generations, around 35 years.

鈥淲e provide evidence for a previously-undocumented and highly-isolated subpopulation of polar bears on the south-east coast of Greenland surviving in a special way,鈥� says at the University of Washington in Seattle. 鈥淭hey survive in fjords that are sea-ice free for more than eight months of the year because they have access to glacier ice on which they can hunt.鈥�

Laidre and her colleagues analysed genetic samples from polar bears that they tracked from 2015 to 2019, which they combined with data from previous studies. In their first discovery, they found a few hundred polar bears in south-east Greenland are the most genetically isolated of their species.

While tracking these animals, the team further discovered this genetically-isolated group hunts via floating blocks of freshwater ice, broken off from glaciers, for about 250 days of the year, when sea ice has melted. This probably enables the bears to live in the area, which has no sea ice for considerably longer than other polar bear habitats.

While this suggests all polar bears are more resilient than we previously thought, glacial ice is largely limited to the animals around Greenland and Svalbard.

鈥淕lacier ice may help small numbers of polar bears survive for longer periods under climate warming, and may be important to prevent extinction, but it is not available for the vast majority of polar bears,鈥� says Laidre.

鈥淐limate action is the single most important thing for the future of polar bears. Most polar bears in the Arctic depend on sea ice.鈥�

According to at the United States Geological Survey, the findings 鈥渙ffer a ray of hope that other refugia habitats may be available for聽polar聽bears to use, so that they can persist until greenhouse gas emissions are substantially mitigated and sea ice habitat is recovered鈥�.

鈥淏ut ensuring the long-term persistence of a [wild] population of polar bears is ultimately dependent on conserving their sea ice habitat. That will require mitigating greenhouse gas emissions.鈥�

The genetically-isolated bears may have adapted to hunting via freshwater ice, but this doesn鈥檛 make them immune to the effects of climate change.

鈥淚 suspect the Achilles鈥� heel for this group of bears will be ongoing warming that negatively affects the ringed seal population in the area. If the ringed seals don鈥檛 have breeding habitat, the main prey of the bears may disappear,鈥� says at the University of Alberta in Canada.

Images Disneynature

POLAR bears roaming the Arctic wilderness are finding it harder to get an easy meal. As sea ice declines due to climate change, it forces bears onto land, away from their main diet of seals. So, when a dead sperm whale washes up on a beach in Svalbard, a Norwegian archipelago, it is a bit of a gift.

鈥淟uck in Svalbard comes in the form of manna from heaven,鈥� says wildlife film-maker Jeff Wilson, who was in the region directing the Disneynature film , which includes footage of bears feeding on the whale carcass.

When food is plentiful, competition between the bears is reduced. 鈥淭hat鈥檚 when you get really interesting interactions,鈥� says Wilson. 鈥淚t was just a whole bunch of bears happy in their own skin, playing with one another.鈥�

Wilson thinks the carcass was feeding bears for a second consecutive year, re-emerging after a winter under the ice. 鈥淲e believe there鈥檚 about 3 billion calories in a sperm whale,鈥� he says.

This free meal may be a relief for the bears, but a 2020 paper suggests that Arctic polar bear populations could be jeopardised by 2100. 鈥淸Their] future is very bleak,鈥� says Wilson. 鈥淪olutions depend on humanity shifting its lifestyle and energy consumption if polar bears are to have any chance at all.鈥�

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An extreme lack of sea ice in Canada this winter should serve as a 鈥渨ake-up call鈥� for the risk climate change poses to polar bears, say conservationists.

Ice normally starts building up across Hudson Bay in November, but the area has remained almost entirely ice-free in the face of temperatures 6掳C above average. In the north-western part of the bay, ice extent . In an average year, 70 to 80 per cent of this part of the bay is covered in ice by this stage in the year.

That has left polar bears standing by the shore, waiting for the ice to form so they can hunt seals. Temperatures in recent days have begun dropping and the US . But the agency says the current low is 鈥渆xtreme鈥� and, across the bay as a whole, second only to 2010 for this time of year.

鈥淚t鈥檚 very unusual. It鈥檚 very low,鈥� says at WWF Canada. 鈥淚 don鈥檛 think this is panic and everything is collapsing, but it鈥檚 indicative of the broader trend [of sea ice loss].鈥�

Climate change has .

鈥淚t鈥檚 not good [for the bears],鈥� says , an ecologist at the British Antarctic Survey. 鈥淭he longer they don鈥檛 have sea ice, they get a gradual loss in condition. A lot will survive it [this year]. But it tips the balance towards stress-related mortality. Fewer will survive.鈥�

Research suggests that almost all the world鈥檚 remaining 26,000 polar bears will be pushed to the edge of their fasting limits by the end of the century due to climate change. Laforest says that while bears in the high Arctic are currently doing fine, the sub-population in the Hudson Bay area are the canaries in the coal mine.聽

鈥淭hey are the first to go through these broad implications of climate change,鈥� he says. 鈥淲e need to take these warning signals for what they are. It鈥檚 a wake-up call.鈥�

The remote nature of the region in which the bears hunt, and the cost of tracking them, means it will be hard to measure precisely what impact this year鈥檚 late freeze has on the animals. In the meantime, Laforest says there may be more human-wildlife conflict as hungry bears wander into Inuit communities in search of food. The late ice is also impacting people in the region, he says, as they cannot access their usual hunting grounds.聽

The National Snow and Ice Data Center says the picture for the Arctic as a whole is mixed, with sea ice extent only the tenth lowest on record for November. On the Russian side of the Arctic, sea ice growth has been above average in the Bering Sea, trapping ships in ice and disrupting supplies to Siberian cities.

Unchecked climate change will doom all but one of the world鈥檚 populations of polar bears before the end of the century, as vanishing sea ice increases their annual fasts beyond their limits.

The bears鈥� reliance on sea ice to hunt seals means that the last 26,000 are being pushed towards physiological thresholds for how long they can fast each year as the Arctic warms. However, a lack of data on the demographics of the 19 sub-populations of polar bear has made it hard to give accurate timelines of how long each group will be able to continue in the future.

To bridge the gap, P茅ter Moln谩r at the University of Toronto and his colleagues emulated the approach taken by climate scientists to model future temperatures. For each of the 19 bear groups, they combined estimates of the extent of sea ice for their part of the Arctic with how much energy they need daily and how fat they are before each fasting season to build an 鈥渆nergy budget鈥� computer model. This projected how long they will be able to keep reproducing and surviving.

鈥淭he bottom line is very simple. If we continue greenhouse gas emissions the way we are doing, it is highly likely we are going to lose every polar bear population in the world before the end of the century, except perhaps in the very high north of the Arctic, in the Queen Elizabeth Islands,鈥� says Moln谩r of a high-emissions scenario where temperatures rise by almost 4掳C globally by 2100.

Even if emissions are cut dramatically and warming is held to just under 2掳C, most of the bear groups will still be pushed beyond their physical limits 鈥� though聽some will probably survive this century.

The researchers tested their model with 鈥渉indcasting鈥�, comparing its projections for the past with actual historical observations. For example, it neatly matched the waxing and waning of the bears in western areas of Hudson Bay, Canada, in the 1980s and 1990s.

The study was only able to model 13 of the 19 groups because there weren鈥檛 detailed enough climate models for the other six, though Moln谩r says he has no reason to think they would respond differently. He says the dire projections are conservative because for every uncertainty 鈥� such as how fat future bears will be when they start fasting 鈥� the researchers erred on the optimistic side.

Mark Lewis at the University of Alberta in Edmonton, Canada, who wasn鈥檛 involved in the study, says the energy budget model underpinning the research is sound and the hindcasts are impressive. Moln谩r says that while it may seem like 鈥渏ust another polar bear doom-and-gloom story鈥�, the research shows cutting emissions can make a difference. 鈥淭here is no alternative way.鈥�

Being a polar bear is harder work than biologists thought. As the bears roam the Arctic sea ice hunting seals, they use more energy than expected. That has ominous implications for a future in which sea ice is ever scarcer.

of the US Geological Survey in Anchorage, Alaska, and his colleagues studied 9 adult female polar bears on the Beaufort Sea ice north of Alaska. They fitted the bears with collars carrying GPS trackers, accelerometers and video cameras. They also injected the bears with water labelled with stable isotopes of hydrogen and oxygen.

When the team recaptured the bears 8 to 11 days later, changes in the ratio of isotopes in their blood gave a measure of metabolic rate. The researchers could compare this with the bears鈥� activity and hunting success.

Researchers already knew that polar bears are inefficient walkers, but many assumed that they also saved energy by sitting quietly waiting for seals, and by reducing their metabolic rate when fasting. However, it seems these savings are small at best. The bears鈥� average metabolic rate during the study period was 1.6 times more than most previous estimates.

Not so thrifty

This means the bears must kill and eat more seals over the course of a year, to pay for this higher metabolic rate.

But as climate change melts ever more sea ice, the bears are likely to have to walk farther to find prey. 鈥淭hat has a cost, and the animal has to find the energy to do that 鈥� or take it out of growth, reproduction, or survival,鈥� says polar bear biologist at the University of Alberta in Edmonton, Canada.

Though Pagano鈥檚 study focuses on just one population of polar bears, many of the other populations around the Arctic likely face the same challenges, says Derocher.

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Climate change may be driving more aggressive polar bears towards areas where people live, and the consequences could be lethal.

鈥淵ou鈥檝e got this perfect storm set up where you鈥檝e got bears that are spending increasing amounts of time on land becoming nutritionally stressed, moving into areas of human settlements,鈥� says , a wildlife biologist at the US Geological Survey. This makes the bears more likely to come into conflict with humans.

Atwood was a member of a team that combed through nearly 150 years of records of bear attacks in Canada, Greenland, Russia, the US and Norway. They drew their data from government agencies, news reports and, in the older cases, from ships鈥� logs.

Between 1870 and 2014, they found 73 cases of polar bears attacking a group of people or an individual, with 63 people injured and 20 people dead. Bears were acting in a predatory manner in most attacks, and it was male bears that were more often involved.

Where details were available, the researchers assigned the attacking bear a score reflecting its body condition. It turned out that 61 per cent of these bears were in 鈥渂elow average鈥� condition 鈥� a situation Atwood says is down to them not finding as much food because of dwindling time on sea ice, their habitual seal hunting ground.

Polar bear attacks averaged around eight or nine per decade, Atwood says, but from 2010 to 2014 alone there were 15. 鈥淭hat does lead you to hypothesise that around 2000 we might have hit a shift in the kind of conditions in the Arctic.鈥�

Encounters increasing

at the American Museum of Natural History in New York says that the study is a step in the right direction. 鈥淚t鈥檚 a good move because we are going to have increasing encounters with bears. Some of it is due to climate change 鈥� more bears are going to come on to shore,鈥� he says.

While he agrees that bears in suboptimal condition are feistier, he disputes the idea that bears moving on to land will always be starving. Instead, he argues that they could in some cases be supplementing their diets by exploiting , and other foods.

Yet another issue could be at play. Rockwell says that with more tourists going on polar bear tours, the animals are becoming more used to humans. During his work on the western side of Hudson Bay, he has noticed that the bears have become harder to deter. 鈥淭hey鈥檙e becoming habituated to noise, they鈥檙e becoming habituated to people,鈥� he says.

All things are relative in the world of bears, though. Atwood鈥檚 paper cites another that found 63 cases of black bears causing deaths from 1900 to 2009 in North America alone. 鈥淚t would appear that polar bear attacks are relatively rare when you compare them to brown bear and black bear attacks,鈥� he says.