Seth Borenstein, Associated Press Yahoo News 25 Apr 08;
The polar bear has become an icon of global warming vulnerability, but a new study found an Arctic mammal that may be even more at risk to climate change: the narwhal.
The narwhal, a whale with a long spiral tusk that inspired the myth of the unicorn, edged out the polar bear for the ranking of most potentially vulnerable in a climate change risk analysis of Arctic marine mammals.
The study was published this week in the peer-reviewed journal Ecological Applications. Polar bears are considered marine mammals because they are dependent on the water and are included as a species in the U.S. Marine Mammal Protection Act.
Scientists from three countries quantified the vulnerabilities that 11 year-round Arctic sea mammals have as the world warms. After the narwhal — which is also known as the "corpse whale" — and polar bear, the most at risk were the hooded seal, bowhead whale and walrus. The ringed seal and bearded seal were least at risk.
"What we wanted to do was look at the whole picture because there's been a lot of attention on polar bears," said study co-author Ian Stirling, a polar bear and seal specialist for the Canadian government. "We're talking about a whole ecosystem. We're talking about several different species that use ice extensively and are very vulnerable."
The study looked at nine different variables that help determine ability to withstand future climate changes. Those factors included population size, habitat uniqueness, diet diversity and ability to cope with sea ice changes.
This doesn't mean the narwhal — with a current population of 50,000 to 80,000 — will die off first; polar bear counts are closer to 20,000 and they are directly harmed by melting ice, scientists said.
But it does mean the potential for harm is slightly greater for the less-studied narwhal, said study lead author Kristin Laidre, a research scientist at the University of Washington.
Stanford University biologist Terry Root, who wasn't part of the study, said the analysis reinforces her concern that the narwhal "is going to be one of the first to go extinct" from global warming despite their population size.
"There could a bazillion of them, but if the habitat or the things that they need are not going to be around, they're not going to make it," Root said.
Polar bears can adapt a bit to the changing Arctic climate, narwhals can't, she said.
While polar bears are "good-looking fluffy white creatures," Laidre said narwhals, which are medium-sized whales, are "not that cute."
The narwhal, which dives about 6,000 feet to feed on Greenland halibut, is the ultimate specialist, evolved specifically to live in small cracks in parts of the Arctic where it's 99 percent heavy ice, Laidre said. As the ice melts, not only is the narwhal habitat changed, predators such as killer whales will likely intrude more often.
"Since it's so restricted to the migration routes it takes, it's restricted to what it eats, it makes it more vulnerable to the loss of those things," Laidre said in a telephone interview from Greenland, where she is studying narwhals by airplane.
The paper is the talk of Arctic scientists said Bob Corell, the head of an international team of scientists who wrote a massive assessment of risk in the Arctic in 2004 but wasn't part of this study. He called it "surprising because the polar bear gets a lot of attention."
Inuit natives of Greenland were telling scientists last year that it seemed that the narwhal population was in trouble, Corell said.
Narwhal More at Risk From Warming Than Polar Bear?
John Roach, National Geographic News 29 Apr 08;
A porpoise with a long, spiraled tusk that inspired the myth of the unicorn ranks higher than the polar bear on a new list of marine mammals most at risk due to Arctic warming.
That's because the narwhal, also known as the corpse whale, may be slightly more sensitive to habitat changes.
All Arctic marine mammals are at risk from warming, which is melting sea ice and shifting the distribution and abundance of prey, the report authors say.
Polar bears rely on sea ice to hunt, and at least one study has suggested that two-thirds of the bears could disappear by 2050 if climate change continues.
But the bears live all over the circumpolar Arctic, and their habitat is unlikely to melt all at once, giving them time to potentially shift their range.
The narwhal, by contrast, mostly sticks to waters between Canada and Greenland (see map), said study leader Kristin Laidre, an oceanographer at the University of Washington in Seattle.
The species' restricted geographic distribution, combined with specific migration routes and a specialist diet, make it just barely more at risk based on the criteria set out for the new analysis, Laidre said.
Her team's report, which ranked the vulnerability of 11 Arctic and subarctic marine mammals, was published last week in the journal Ecological Applications.
Faithful Narwhals
Narwhals spend a few months each summer in ice-free, shallow bays in the high Arctic. In the fall they migrate to deep, mostly ice-covered habitats where they feed.
"They have very specific migration routes and what we call site fidelity," Laidre said.
The animals never vary from their routes and return to the same summer and wintering grounds year after year.
No other porpoises or whales spend much time in the heavily ice-covered regions in the winter, meaning the narwhals face little competition for the Greenland halibut and squid that make up most of their diet.
But as the Arctic warms, different predator species could move in while prey species may move out.
Scientists are concerned that narwhals will be unable to adapt to rapid changes in their ecosystem.
"A contrast is the beluga whale, which is similar to the narwhal but able to exploit many different kinds of habitat in the Arctic and feed on many different kinds of prey species," Laidre said.
Whether or when the changing habitat might drive the narwhal to extinction, she added, is unknown.
Even if most of the population dies out, a few pockets of suitable habitat could remain indefinitely.
Conservation Status
The World Conservation Union lists the narwhal as "data deficient" because too little is currently known about its population status. The animal is also not listed as a threatened or endangered species under the U.S. Endangered Species Act.
Laidre noted that the species' conservation status is outside the scope of her team's assessment.
Should a petition be filed, however, the process may prove less contentious than the current proposal to designate the polar bear as an endangered species, said Kassie Siegel, climate program director with the Center for Biological Diversity in Joshua Tree, California.
Yesterday Siegel's organization won a lawsuit against the U.S. government that requires the Bush Administration to decide by May 15 whether to list the bears.
In its suit, the center alleged that oil and gas development in polar bear habitat has been taking precedence over actions to protect the species.
But the narwhal is found primarily outside U.S. territory, so listing it in the U.S. would offer the animals fewer protections from actions such as offshore drilling.
"We don't have that kind of control over the habitat of the narwhal," Siegel said. "So it wouldn't be as big a deal."
