WAG, Dykstra points out, is scientific jargon for "wild-ass guess."
Since those early days, Amstrup argued, "the scientific ability to estimate the sizes of polar bear populations has increased dramatically." Even so, many uncertainties remain. While the Polar Bear Specialist Group agrees that the species' worldwide population is indeed somewhere within the range of 20,000 to 25,000, there are no reliable estimates at all for the Kara Sea region or the Arctic Ocean basin. Of the nineteen recognized subpopulations, the PBSG was unable, as of its 2009 meeting, to determine status or trends for seven. For those where the data are sufficiently robust, however, the picture is not bright. Three of the remaining twelve are reckoned to be stable, and one, in the Canadian Archipelago, even increasing slightly—albeit from much-reduced numbers as a result of previous overhunting. But fully nine are considered to be in decline, among them western Hudson Bay, the polar bears of Churchill, where additional years of study and number crunching have allowed researchers to calculate with some confidence that these most iconic of all polar bears have decreased in number from approximately 1,200 in 1987 to a little over 900 by 2004.
Some Inuit hunters, noting increases in polar bear sightings near settlements during the time when the ice has melted and the bay is open water, have argued that polar bear numbers are growing, not diminishing. Researchers, in contrast, remain equally convinced by data showing a lack of increase at best, and future or even current declines at worst. Those declines, they fear, will be made only worse by increases in quotas for subsistence hunts, increases made on the basis of the more frequent sightings, sightings that scientists assert are the result of hungrier, more desperate bears coming inshore in search of food.
Such encounters are not restricted to Canada. In northern Alaska, too, polar bears have begun to encroach more on human settlements, sometimes out of apparent desperation, sometimes seemingly because sheer exhaustion robs them of their normal caution and determination to avoid potential danger.
Alaska journalist Charles Wohlforth relays one particularly evocative instance of the latter, as told to him by Barrow biologist Craig George. Summer was reaching its end, and the sea ice of the southern Beaufort Sea had retreated fully 200 miles, by George's reckoning, from the coast. And yet, as if from nowhere, a mother and two cubs swam ashore on the beach near the town. Twice residents used cracker shells to drive the bears back into the ocean; twice they returned. Continued George, in Wohlforth's telling:
Dodging cracker shells, she came ashore a third time and walked right through our crowd of dissuaders, crossed the beach road, and lay down with her cubs, barely 100 yards from the beach and only 10 yards from the road. She seemed to say, 'Shoot me if you must, but I ain't moving. If I go back to sea, I'm dead anyway...' So there she lay with her cubs for two days, barely moving a muscle ... and finally, after two days of comatose rest, she slowly got up and ambled to the coast with her cubs to spend the rest of the fall on the tundra. We never saw her again.
In the waters north of Alaska and Siberia, the Beaufort Gyre has long circled endlessly, a closed loop that gathers ice floes into its embrace and pushes them into and onto each other, creating pressure ridges that rise from the surface of the floes and enormous islands of ice that grow ever thicker, the entire assemblage the perfect combination of stability and volatility, the ice thick enough to provide platforms for seals and bears but active enough to provide multiple openings where seals may breathe and bears may feed.
Since the beginning of the twenty-first century, however, the Beaufort Gyre has been weakening, and warming coastal waters have eaten away at the ice it contains. The thick, stable floes that used to reach all the way to the coast now retreat from it, changing the nature of northern Siberia and Alaska perhaps forever and bringing into question their future as polar bear residences.
"Places like northern Alaska and the northern coast of Russia, the sea ice has historically been close to the shoreline in summer; now it's way offshore and by mid-century it will probably be totally absent," says Steven Amstrup. "If the bears stay with the ice like they have been doing, and the ice retreats farther and farther to the north, is there any sense in them coming back for just a few months in the wintertime when the ice refreezes? Would you migrate a couple of thousand miles for just a short stay and return?"
Yet therein, especially for pregnant females, lies a dilemma. Those that choose to continue denning on the sea ice, as more than half of Beaufort Sea females traditionally have done, will do so on a platform that is thinner, more chaotic, and less reliable than before, that may transport them even farther than previously while they rest in their dens, that could conceivably break apart beneath them. It seems that, as the ice thins and retreats, a greater number of bears than before are now making dens ashore, but this, too, poses its risks. A growing distance between shoreline and ice edge exposes newly emergent cubs to the considerable dangers of being forced to take a plunge before reaching the sanctuary of the sea ice; and while their mother is likely to carry them on her back, her stamina is not limitless. Polar bears are excellent swimmers, it is true, but in swimming too great a distance without respite they risk exhaustion, as in the case of the family described by Craig George, or worse.
Between 1987 and 2003, biologists Charles Monnett and Jeffrey Gleason saw a total of 351 polar bears during aerial surveys off Alaska's Beaufort Sea coast, 12 of which were swimming at the time the aircraft passed over them. In 2004, they saw 55 bears, 51 of them alive, and 10 of those living bears in the water. The 4 dead bears were all floating in the water, and while it cannot be certain that they drowned, it can reasonably be surmised that they did. It is, suggest Monnett and Gleason, a fate that is likely to befall an ever greater number of polar bears as the ice retreats and disappears.
Our story began in what seemed on the surface the most fragile of environments, and it is where we shall end. A layer of snow covering a hole in a drift scarcely seemed adequate protection for a mother to raise her cubs, and yet, in the dark and the warmth, that is what she does. It is, in fact, in many ways the most peaceful and secure experience of a polar bear's life. But that security, too, may no longer be a guarantee.
As temperatures climb in western Hudson Bay, so too does the likelihood of fires in the areas of the Wapusk National Park where forest yields to tundra and, in the other direction, tundra vegetation is slowly subsumed by a forest of spruce and larch. It is here, in the shade and relative cool, that the polar bears of Churchill spend their summer months, curled up in dens dug into the permafrost, dens in which expectant mothers remain in wintertime, digging outward into the snowbanks that cover them up with the onset of fall. But fires caused by lightning strikes sometimes damage those earthen shelters, causing their collapse, and while polar bears returning from the sea ice will investigate dens in burned areas, they rarely decide to remain there, forcing them to keep searching or, possibly, to dig new ones instead of being able to take advantage of those that have existed for generations. It is yet another expenditure of energy that a pregnant female in particular can ill afford to undergo, but one that may prove increasingly difficult to avoid.
Far to Churchill's northwest, researcher Doug Irish was traveling along the coast of the Yukon in June 1989 when, sticking out of a snowdrift, he saw the head of a dead polar bear. Digging into the snow, he realized that he had stumbled across a den that had collapsed; buried in what remained of the dwelling were two small cubs. Given the extreme care and exactitude with which polar bear mothers choose den locations, such collapses are likely exceedingly rare; but in a world where snow is more prone to melt, or heavy rains take the place of some snowfall, they may become less so.
Yet even the most ideal den location, even the most perfect winter conditions, will be to no avail if, as the ice retreats, as seals diminish and become harder to find, as polar bears become hungrier and ever more desperate, a den is no longer a sanctuary but a target.
In January 2004, researchers flying over denning habita
t along the Beaufort Sea coast came across a den that had been broken open. From the den's opening, a trail of blood led to the carcass of a bear. Landing to investigate further, they documented a scene without known precedent. Arterial blood was sprayed along the back wall of the den, into which a great deal of snow and ice rubble had been pushed. Two hundred feet away, the carcass was of a female, the den's occupant. Surrounded by large paw prints, it had been partly devoured.
Examination of a single set of paw tracks shone light in the shadows and completed the picture. An adult male—wandering, meandering, directionless—had suddenly stopped and made straight for the den. Using his massive forepaws, he had smashed through the roof as if it were the lair of a ringed seal. When the roof caved in, the snow buried two young cubs, but the male was after larger prey. His massive limbs held the mother down as he bit at her head and neck, severing her artery and penetrating her skull. Then he dragged her into the open and began to eat her.
Cannibalism in polar bears is not without precedent. It is to avoid this prospect that females keep cubs close by and build their dens far away from areas where male bears are likely to roam. But such incidents as do occur are almost always the result of accidental encounters; when females are killed and sometimes eaten, it is likely in defense of their young. Never before had any of the researchers involved seen anything quite like this, never before had there been any record of a male actively breaking into a den and killing a female.
Three months later, the same researchers followed the tracks of a female which, having lain undisturbed during her denning period, had emerged with one cub in tow. The tracks led to a pressure ridge, where she had lain down in the snow and nursed her cub. It would be the last meal she offered, and the last the cub consumed. Just beyond the ridge, she lay dead, overwhelmed, killed, and eaten by a much larger bear. The tracks of the fleeing cub continued for a short while but then were lost.
And just three days after that discovery, the researchers made another: an adult male feasting on a yearling, which had been stalked and killed while it lay in a small pit in the snow. A rash of paw prints in the vicinity may have belonged to the dead cub's mother and siblings; but of the bears themselves there was no sign.
Many of the living bears the researchers found that year were in relatively poor condition; while offering the usual caveats of scientific uncertainty, they did not hesitate to suggest a relationship between the existence of thin bears and cannibalized ones. In twenty-four years of fieldwork in the southern Beaufort Sea, they wrote, never before had they come across signs of polar bears actively stalking and killing other polar bears.
Previously unseen, also, was the tragic tableau witnessed on the tundra of Hudson Bay, just outside Churchill, on November 20, 2009. The fall season had been warm and long; the shores were densely packed with hungry bears awaiting the sea ice that had yet to form. The visitors that day did not see the attack itself, did not document the moment when the male had attacked and killed the cub, but observed the aftermath. A struggle of sorts was evident as they approached; by the time they arrived on the scene, the cub was dead, the distraught mother alternately charging and then circling its killer. Perhaps attracted by the scent of death, other bears arrived; the male, which had begun to consume his quarry among some willows, moved the carcass to the coast to finish his meal in relative peace. The mother, as if still not able to fathom what had taken place, wandered the area looking frantically for her offspring. Where the male had begun to feast, she found her cub's pelt; picking it up in her mouth, she carried it away, swinging her head from side to side in obvious distress. Charging the other bears to keep them away, she kept the pelt firmly in her mouth until, finally, she placed it gently in the snow among the bushes, protected from the wind.
In 2007, in response to demands from environmentalists that it protect polar bears under the federal Endangered Species Act, the Bush administration directed the USGS to provide its best assessment of the species' status and future. The response was not encouraging.
Based on the best available estimates of climate trends and the likely response of sea ice to those trends, USGS scientists concluded that, by the middle of the twenty-first century, two-thirds of the world's polar bear population may have disappeared. It is possible, they wrote, that polar bear populations can survive in the Canadian Archipelago through the end of the century; if they do so, they could be the species' last survivors, and they would be much reduced in number. Elsewhere, polar bears would likely cease to exist within seventy-five years, and in some parts of their range—such as Hudson Bay and the southern Beaufort Sea—they could be gone within forty-five.
"I'm sure we'll still have polar bears around by the middle of the century and probably by the end of the century," says Steven Amstrup, the study's lead author, "but they'll be limited to portions of the Canadian High Arctic and adjacent Greenland, where the sea ice remains for longer, so they'll still have enough time to forage on marine mammals...[and] can survive through those periods when the ice is absent."
In a few select places, such as perhaps Wrangel Island, they may be able to persist by feeding on walruses that have themselves been forced ashore; but for the vast majority, living on land will not be an option. The brown bears that live in the regions where any newly terrestrial polar bears would be forced to try and eke out a living are the smallest brown bears in the world, and they are sparsely distributed, because the environment can support only grizzlies that are relatively tiny and few in number.
"It seems highly unlikely, then, that you could take the largest bears in the world and plunk them down on land in a habitat that only supports a very spare population of some of the smallest bears in the world," observes Amstrup. "You wouldn't do that and expect the polar bears to be able to survive. One thing we know is, polar bears don't go running around trying to figure out how to catch different kinds of food. Nowhere that we're aware of have they been successful in garnering much energy from anything except marine mammals that they catch from the sea ice."
Polar bears, in other words, may have descended from grizzlies, but there is no turning back to be like them again. They took a fork in the evolutionary road, and the path they have followed leads in only one direction. Polar bears have evolved to exploit a particular environment, a specific niche. In so doing, they have become a supremely successful predator, but while they may be the dominant predators in their chosen realm, without it they are doomed.
Polar bears are creatures of the sea ice. If it disappears, so will they.
The warmth of the freshly slain seal enveloped his face; its scent flooded his nostrils. At long last, the wait was over. The sea ice had returned, and with it a chance to satiate his hunger. He tore chunks of blubber from his victim, swallowing them ravenously as if he had no time to chew, so desperate was he to fill the void inside him.
The wait had been longer this year, the fast more demanding. It had eaten at him, increased his yearning for the hunt, a yearning that burned inside him still even as he devoured his first kill of the season. In others it had created desperation; one young male, anxious not to have to travel any farther after months without food, had even attempted to approach the breathing hole he had so studiously staked out. Such an act of impudence, and one he had punished, driving the intruder away until, defeated, the thin youngster had lain down in the snow and seemingly surrendered to the inevitable. As he swallowed, he looked over his shoulder to check that the stranger was not attempting to snatch his meal, but the interloper was not moving, showed no sign of stirring at all in fact, but remained where he lay, not offering any resistance as the drifting snow slowly covered him up.
The meal was finished. Only the remnants of a carcass remained. Still he was hungry. He closed his eyes and lifted his nose, sampling the scents that wafted through the air. He opened his eyes again and scanned the horizon. It was fiat, and still. He sniffed the air some more and then set off on his journey, across the ice.
Future
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nbsp; The Nares Strait is a narrow sliver of a passage, an undersized intermediary sliding between the closest points of Greenland and northeast Canada. The multichromatic mountaintops of Ellesmere Island glisten to the west, a giant's fingertips away from the slightly less imposing cliffs of Greenland to the east.
On a map it is barely noticeable, a cigarette paper's width lost in the morass of channels and islands of the Canadian High Arctic. For much of its recorded history, it has been a navigable passageway in name only; in winter, it is thick with sea ice that in summer melts and breaks apart one section at a time, granting only limited and temporary access.
The first section, toward the strait's southern end, normally breaks apart in late June, but its fracture provides no guarantee of a clear pathway. The ice takes weeks to fully break up and drift south, and it does so in the form of large floes and ice islands that are a navigational peril. By the time something approaching a negotiable route to the north opens up, a second restraining ice bridge—at the strait's very northern limit, on the boundary of the Robeson Channel and the Lincoln Sea—starts to fracture, flooding Nares Strait with old, multiyear sea ice from the Arctic Ocean.
In terms of oceanography and climate, that makes the Nares Strait, for all its apparent anonymity, of extreme importance, because it is one of only two outlets through which the Arctic Ocean can expel ice. But it also makes further passage precarious and ultimately—as temperatures drop with the onset of autumn and the ice fuses into an impenetrable barrier—once more impossible.
Prior to 1948, only five vessels had ever been recorded as traveling even as far north as Kane Basin, a slight bulge that marks the strait's approximate midway point. The ships that had pushed north of that point in the subsequent half-century were also relatively few in number, primarily powerful icebreakers that could grind through the gnarled floes. But now, at the end of June 2009, a small green ship—an icebreaker, yes, but on a far smaller scale than the behemoths that preceded it—sails defiantly and without interruption. On each flank of the ship's hull a rainbow rises from the waterline toward the bow, culminating in a white dove. Above the doves, in white lettering on either side, the ship's name.
The Great White Bear Page 22