Defenders Magazine

The Ice Bear's Melting World

Can polar bears survive as the planet warms?

by Nick Jans

© Nick Jans

I stand numb-faced in the wind, leaning into my binoculars. Across a lagoon of Alaska's Beaufort Sea lies a low barrier island, and along its beach, ghost-like shapes drift in the growing dusk: polar bears—females with cubs, young adults and a few huge males. U.S. Fish and Wildlife Service biologist Susanne Miller and her team had counted 37 bears earlier this September afternoon on the barren, 3-mile-long sliver of surf-battered sand near Kaktovik, an Inupiaq village in the northeast corner of the state. Since 2002 Miller and her team have been studying the bears here, in a setting that, despite its location far above the Arctic Circle, seems increasingly un-polar.

"Polar bear use of the coastline during the open-water period appears to be increasing," says Miller. "It's a dynamic, complex situation. Things are changing fast."

The bears' usual habitat, the ever-shifting pack ice of the Arctic Ocean, lies more than 150 miles north—beyond the reach of many of these marine mammals, strong swimmers though they are. Until autumn's deepening cold forms new ice, they'll be stranded here far from their natural prey, as some have already been for two months. Eerily warm conditions in the western Arctic during the past decade have caused an unprecedented melt-off of the ice on which the polar bears depend. The Kaktovik bears have whale carcasses left nearby by Inupiaq hunters, enough to tide them through the always-lean thaw season. Other bears stranded onshore along the coast might not be so lucky.

"When I was growing up, only rarely did we see polar bears nearby," says 51-year-old Kaktovik resident Joe Soplu. "Now, every summer there are lots of bears on the edge of town, and the ice is so far we only hear about it. We used to hunt seals in drifting ice, right out there." He gestures past the barrier island to the iceless gray chop beyond—where bears, too, once hunted seals at this time of year. Soplu and elders like Daniel Akootchook, 77, look out at an utterly changed world, bemused as if palm trees had sprouted on the shores of the Beaufort Sea. "No more 40 and 50 below [zero]. Summer year round," Akootchook jokes. But deep concern leaks through his smile.

Such is the strange, new world, increasingly without ice, in which polar bears struggle to survive. Over the past year, a well-publicized concern over the future of this species has escalated to alarm as new data trace global warming's impact on the animals and their Arctic habitat. In September, the National Snow and Ice Data Center reported a record-setting summer retreat of the polar ice cap for 2007. The thickness of ice, as well as its age, has also diminished significantly across the northern polar region in the past two decades—evidence that the meltdown has reached a critical stage, which may result in a seasonally ice-free Arctic Ocean by 2030.

"I find the rate of ice loss troubling," says Mark Serreze of the snow and ice center. "It's three times faster than our most aggressive models predicted."

The world's polar bear population is expected to diminish by two-thirds by 2050, and core habitat to decrease by 42 percent, according to a U.S. Geological Survey (USGS) study released in September. That translates to a decline of perhaps 15,000 animals—and the total loss of polar bears in the southern extent of their range, including Alaska. While pollution, hunting, industrial development and even ecotourism pose concerns, these threats pale in comparison to climate change, which is more pronounced in the western Arctic than just about anywhere else on Earth. Polar bear researcher Steven Amstrup of USGS gives the bottom line in simple terms: "As the sea ice goes, so goes the polar bear."

If any doubts remain among the scientific community or the general public concerning the bears' plight, they're evaporating like snowdrifts beneath summer sun. Responding to a petition submitted by several environmental groups, the U.S. Fish and Wildlife Service in December 2006 proposed a formal "threatened" listing for polar bears under the Endangered Species Act. Federal officials received more than 600,000 comments from the public on the proposal, nearly all in favor of protection. "We were a bit overwhelmed by the sheer volume," says Miller. "There's obviously a high level of public concern." (The agency's decision on listing was pending as this article went to press.)

The signs of increasing stress among Alaska's and Canada's western Hudson Bay populations have been noted by biologists: diminishing cub survival; decreasing weight and skull size both among new cubs and adult bears; previously rare cases of starvation and bears hunting and eating other bears; increasing numbers of bears stranded onshore in northern Alaska during the summer; and ominous sightings of drowned bears floating a hundred miles from the nearest ice. In western Hudson Bay, on the southern edge of the polar bear's current range, bear numbers have declined 22 percent since the mid-1980s. Population estimates for Alaska's southern Beaufort Sea have dropped from more than 1,800 in 1987 to about 1,500 in 2006, a decrease of more than 16 percent.

The findings of the USGS report are both bleak and blunt: If the summer melt continues to accelerate and the fall freeze occurs later and later in coming years, as predicted by climatologists, the polar bear populations of western Hudson Bay, Russia and Alaska will decline until they simply cease to exist. Yet some hope remains: some bears in the Canadian Arctic Archipelago should survive into the next century.

To the Inupiat, he's nanuq; to the Russians, beliy medved, or "white bear"; scientists call him Ursus maritimus, "sea bear." Of all the names given to the species by various cultures, perhaps the most telling is the Norwegian isbjorn, or "ice bear." These marvelously adapted creatures were shaped by the relentless force of the northern ice cap, and evolved in its shadow. Genetic analysis and fossils provide insight on the species' development. During the middle Pleistocene epoch, 100,000 to 250,000 years ago, a population of brown/grizzly bears was isolated by the polar ice sheet's gradual advance, and responded in remarkable fashion. Through natural selection over generations, they became lighter in color, better insulated and more buoyant, with streamlined shapes and paddle-like paws adapted for swimming between ice floes. Morphing from land-based, opportunistic omnivores into carnivores of the polar ice, they became dedicated to the pursuit of ringed seals and other seal species. 

The largest male bears exceed 1,700 pounds, and a mature male averages around 1,000. The smaller females generally weigh less than half that. Polar bears mate in the spring, and pregnant females dig multi-chambered dens on land or on thick, stable ice in the fall. While males and juveniles remain active through the winter, the denned females, in a state of near hibernation, give birth. Litter sizes are usually two to three; the blind, helpless cubs weigh about a pound each. Nursing on cream-like milk as the mother dozes, the young bears rapidly gain weight. By the time the family emerges in March, the cubs will be 20 to 30 pounds, and soon add meat to their diets as their mother hunts. Fully dependent during that first season, cubs will usually remain with their mother for about two and a half years.

But many cubs don't live that long. A cub has only a 43 percent chance of surviving past its first year in the southern Beaufort Sea at present, compared to a 61 percent survival rate in the late 1980s and early 1990s—a significant decline, especially since a female can produce a litter only every three years in the best of conditions. If her body fat reserves aren't sufficient—which depends on feeding conditions during the thaw season—a female will re-absorb fertilized eggs. The implication is clear: Reproduction in declining, food-stressed populations may plummet past recovery.

If a bear survives past the first tenuous years of life, it may live for a quarter century or more. Under normal conditions, humans are their only significant predators. Sport and subsistence hunting, which decimated many polar bear populations in the 19th and 20th centuries, was drastically reduced by international treaty in 1973. Regulation allowed polar bears to rebound to their current levels—only to face a larger, far more complex crisis that threatens not only them, but the entire Arctic environment, and other species and habitats worldwide.

The World Conservation Union recognizes 19 distinct sub-populations of polar bears, some as small as 100 animals, the largest numbering more than 3,000. Worldwide, roughly 20,000 to 25,000 bears are thought to roam the shifting ice of the Arctic Ocean, though data for most populations remains sketchy. Rimmed by northernmost Eurasia and North America, this harsh, unforgiving environment covers more than 5.4 million square miles, and is bordered by thousands of miles of coastline where human settlements are few, and scientific access difficult. Nonetheless, thanks to the efforts of determined researchers and modern technology, understanding of the bears' biology and movements has greatly improved. "So much of what we've learned has been through [satellite] tracking collared bears," says Miller.

Polar bears concentrate near the dynamic, shifting edges of pack ice over the continental shelf where seals congregate near leads (large, shifting cracks in the ice) and polynyas (ice-free areas created by currents and upwellings). Individual bears routinely travel huge but distinct ranges that may cross national boundaries and international waters. One female fitted with a satellite tracking collar near Prudhoe Bay in northern Alaska covered more than 3,000 miles in a single year, her itinerary including Greenland and Canada's Ellesmere Island.  

Biologists have identified four distinct ecoregions currently inhabited by polar bears, each with unique ice characteristics, and differing predictions for bear survival over the coming decades: seasonal, where ice is regularly absent during the summer melt; polar divergent, where ice recedes in summer and/or is moved offshore by prevailing winds and currents; polar convergent, where in summer drifting ice is driven into shore; and archipelagic, characterized by northern islands with irregular but pervasive ice conditions near shore. Bears inhabiting the latter are given the best odds of surviving into the next century. Those in the seasonal and divergent regions (the second includes northern Alaska) are likely to disappear by mid-century.

The crisis facing the polar bear raises two questions. First, what do the bears require for survival? Experts are certain of the prime necessities: seals, pack ice on which to hunt them, plus large areas free from human disturbance. Despite their fearsome reputation, most polar bears tend to be remarkably shy; Amstrup likens them to "grizzlies on valium." Hunting or denning bears may be easily displaced by human activity, especially by summer oil exploration on ever-shrinking patches of prime hunting ice. Almost all seals are caught not in the water, but on that platform—mostly by waiting in ambush near breathing holes.

Bears on land will certainly gorge on a whale carcass if it presents itself; scavenge bird eggs and plants; or even attempt to chase caribou, as hunters from Kaktovik recently witnessed. But polar bears are true marine mammals, too specialized and too large to survive on the Arctic's meager terrestrial offerings for extended periods of time, and incapable of evolving with the current rate of change. Simply put, without ice, most of the world's polar bears are doomed. The sharp decline of western Hudson Bay's bears, stranded for ever-lengthening periods during the seasonal melt, seems a grim illustration of that point, and a harbinger of the future.

The second question: What can we do? The recent USGS report seems to ring with finality, the sense that the loss of most or all of the world's polar bears is sad but inevitable. Amstrup, one of the report's authors, bristles at that interpretation: "There's nothing in our studies that indicates this outcome is irreversible." He points out that more than 800 scientists of the Intergovernmental Panel on Climate Change, in their landmark 2007 findings, stated with 90 percent probability that humans are major contributors to global warming.

"I'm hopeful that we're past the denial stage," says climatologist Serreze. "The uncertainty lies in the future of greenhouse emissions. It's up to us." Amstrup adds, "At worst, reducing carbon dioxide emissions now may take 40 years to take effect, and we predict we'll have polar bears surviving in the Arctic Archipelago then. They can repopulate. There's still time."

For those who study and admire ice bears, whether from afar or up close, time is of the essence. "Each year, out in the field, the first polar bear of the season is magical," says Amstrup. "And I've been working on them for 26 years. They're such spectacular creatures. It's hard to imagine Alaska without them."

Alaska writer Nick Jans contributed to The Last Polar Bear, a book combining the images of Steven Kazlowski and essays on the bears and climate change (The Mountaineers Books, Feb. 2008).