“Polar bears are one of nature’s ultimate survivors, able to live and thrive in one of the world’s harshest environments, but we are concerned the polar bears’ habitat may literally be melting,” Secretary of the Interior Dirk Kempthorne said on introducing a proposal in December 2006 to list the bears as an endangered species.
His plan allows a year for data review by the U.S. Fish and Wildlife Service “to broaden our understanding of what is happening with the species,” before a final determination on whether to list the bear as endangered.
New data demonstrating high rates of melting ice over the past several years have alarmed scientists. A recent study by Colorado-based National Center for Atmospheric Research (NCAR) shows that the Arctic Ocean could lose nearly all of its summertime ice by 2040. That could spell doom for polar bears.
“We have already witnessed major losses in sea ice, but our research suggests that the decrease over the next few decades could be far more dramatic than anything that has happened so far,” NCAR scientist Marika Holland said.
Bear populations that increased after restrictions on hunting in their range countries are now again in decline, the Polar Bear Specialist Group reported in 2005. The number of polar bears in the wild now is estimated at 20,000 to 25,000.
Warming affects polar bears more than other species because they live on the disappearing ice, a habitat to which they are specifically adapted. Environmental toxins also take their toll. Polar bears are at the top of the food chain, so “they integrate all the changes that take place” in species below them, says Steven C. Amstrup, polar bear project leader at the U.S. Geological Survey (USGS) Alaska Science Center in Anchorage.
Amstrup, who has researched polar bears for nearly 30 years, told USINFO: “As far as rescuing polar bears before their habitat disappears, there is really no rescue.” As sea ice declines, he said, so does their capacity to hunt for their primary food, the ring seal. “Polar bears are entirely dependent upon the sea ice because it is only from that platform that they are able to harvest the bounty from the sea,” Amstrup said.
The quality of ice appears to matter, too. “Not all ice is equal in the eyes of polar bears,” said George Durner, research zoologist with the USGS Alaska Science Center. Durner studies how bears use the habitat.
Although they adapt readily on the harsh ice fields, polar bears do not thrive on land. Of the 19 polar bear populations that live in the Arctic, those on the Hudson Bay have been forced to spend part of the year on the shore, but they do not significantly feed there.
To survive summers on land, they bulk up on high-energy seal and walrus diets during the winters, but shorter winters reduce their ability to feed sufficiently. Food sources available on shore do not offer the rich nourishment these giant bears require.
Less ice and less time to feed leave the bears malnourished and vulnerable. Low reproduction and high mortality rates for cubs further reduce their numbers. Since 2004, several incidents of polar-bear cannibalism have been documented, something not seen previously, according to Amstrup.
Polar bears have drowned while trying to swim the increasing distances from one ice platform to another – also a disturbing trend. Although strong swimmers, polar bears are not aquatic mammals, Armstrup said.
Polar Bears and Climate Change
Few scientists question whether climate change is occurring, although they continue to study and debate its causes. Durner told USINFO there are many contributing factors: “It’s not just CO2 [carbon dioxide] emissions, but there are other atmospheric processes,” such as “wobbles in the earth’s orbit that may be responsible for some of the changes …. It is not a simple issue at all.” But the charted upswing in global warming since the industrial revolution indicates “human activity” as a significant contributing cause.
Armstrup emphasized the importance of continuing investigation, “The right kind of research will help us provide the kinds of information that will allow managers to adapt their actions to whatever the future needs of polar bears are.” This means fieldwork – and funding. Research will help the bears that remain, “but will not address saving their habitat.”
“The consensus among scientists, that humans are mainly responsible for the warming climate, is greater than any scientific issue of which I am aware,” Amstrup said. “If this huge body of scientists is right, the way to reverse this trend is to reduce greenhouse gas emissions.” He and others agree that it is not too late for recovery. NCAR’s Holland concurs: “Our research indicates that society can still minimize the impacts on Arctic ice.”
In February 2002, President Bush committed the United States to a strategy to reduce the American economy’s greenhouse gas intensity (how much is emitted per unit of economic activity) by 18 percent by 2012. Since then, the United States has spent billions of dollars on climate-change programs, energy tax incentives and climate-change-related international assistance programs.
Quick action is vital, but not only to save the bears. If the NCAR study is correct, Amstrup said, “The ramifications of that for polar bears and our ecosystems, if it were to come to pass, are very significant, indeed.”