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Polar Bears Far from ‘Strong and Healthy’

Alaska Sen. Lisa Murkowski said the “latest research” shows “polar bear numbers are strong and healthy” in her state. That’s false. Polar bears are listed as “threatened” under the Endangered Species Act. Of the two polar bear populations in Alaska, one is declining, and the status of the other is unknown, according to the latest research.

Murkowski was responding in a statement to a Feb. 29 court decision that granted permission to the Fish and Wildlife Service to designate roughly 187,000 square miles as critical habitat for polar bears in Alaska. The decision reversed a Jan. 10, 2013, lower court order, which ruled that the FWS had failed to provide “adequate justification” for its designation to the state of Alaska and that the critical habitat “went too far and was too extensive,” among other reasons.

The Feb. 29 court decision, however, ruled that “the FWS’s designation of polar bear habitat was not arbitrary, capricious or otherwise in contravention of applicable law.” The FWS says the designation of critical habitat doesn’t necessarily restrict development, but “activities that involve a Federal permit, license, or funding, and are likely to destroy or adversely modify critical habitat will be affected.” Murkowski took issue with the court decision:

Murkowski, Feb. 29: The most up to date research and traditional knowledge indicate that polar bear numbers are strong and healthy across Alaska’s Arctic. It is clear once again that decision makers outside of Alaska are overreaching and do not understand the impact this will have on those who live, work, and raise families in the Arctic.

The Feb. 29 court ruling explained that the Endangered Species Act requires the FWS to designate critical habitat areas within a year of listing a species as threatened, though extensions can be requested.

SciCHECKinsertOn May 15, 2008, the Department of Interior, at the suggestion of the FWS, listed the polar bear as “threatened” under the ESA. The FWS proposed its designation of polar bear critical habitat on Oct. 29, 2009.

As the Feb. 29 court document explains, the FWS’ “proposal drew fire from oil and gas trade associations, several Alaska Native corporations and villages, and the State of Alaska … all of which seek to utilize the natural resources in Alaska’s waters and North Slope that make up much of the designated habitat.” When the FWS granted final approval of the critical habitat on Dec. 7, 2010, these groups challenged the action in court.

We take no position on the legal dispute. But we can say that polar bear populations in Alaska are not “strong and healthy,” according to the most recent research and the conservation status listings of multiple organizations.

Southern Beaufort Sea Bears

There are two polar bear populations in Alaska: the southern Beaufort Sea population and the Chukchi Sea population. To justify listing these bears as “threatened,” the Department of Interior argued:

Department of Interior, May 15, 2008: We find, based upon the best available scientific and commercial information, that polar bear habitat — principally sea ice — is declining throughout the species’ range, that this decline is expected to continue for the foreseeable future, and that this loss threatens the species throughout all of its range.

Since 2008, research on Alaskan polar bear populations has found similar trends, especially in the southern Beaufort Sea population.

In April 2015, Jeffery F. Bromaghin, a statistician at the U.S. Geological Survey, and others published a study in the journal Ecological Applications, which found that roughly 900 polar bears made up the southern Beaufort Sea population in 2010. That’s down from 1,526 bears in 2006 — over a 40 percent decline.

The team observed that survival rates from 2004 through 2006 were particularly bad, but that the “survival of adults and cubs began to improve in 2007 and abundance [or population size] was comparatively stable from 2008 to 2010.” However, the “survival of subadult bears declined throughout the entire period.”

Earlier studies on the body condition of these bears also indicate this population isn’t “strong and healthy.” In 2010, Karyn Rode, a wildlife biologist at the USGS, and others, published another paper in Ecological Applications, which found that the mean skull size and body length of 3-plus-year-old polar bears in the southern Beaufort Sea declined from 1982 to 2006.

This is a problem because “[r]ates of reproduction and survival are dependent upon adequate body size and condition of individuals,” the authors explain. A 2006 USGS report also found similar trends in the body condition of southern Beaufort bears.

Bromaghin told us by email that his 2015 paper is the “most recent information regarding the status of the Southern Beaufort Sea population,” but that he and colleagues are in the “early stages of developing an updated population assessment that will include data collected since 2010.”

We contacted Murkowski’s office to ask what she meant by “most up to date research” on polar bears. Jenna Mason, a press assistant in Murkowski’s D.C. office, referred us to a 2013 Global Change Biology paper by Rode and others.

This study found Chukchi Sea polar bears appear to be faring better than southern Beaufort Sea bears. But the paper didn’t provide any evidence to support Murkowski’s claim that “polar bear numbers are strong and healthy across Alaska’s Arctic.”

Chukchi Sea Bears

Overall, less is known about the Chukchi Sea polar bear population. Bromaghin told us scientists “do not have quantitative estimates of survival or abundance for that population” at present.

However, the aforementioned 2013 study did find that, between 2008 and 2011, Chukchi Sea “polar bears were larger and in better condition, and appeared to have higher reproduction than [southern Beaufort Sea] bears.” The paper’s authors hypothesized that these population differences resulted in part from the fact that “twice as many bears were fasting in spring” in the southern Beaufort than the Chukchi Sea region.

The team also found that there were “twice as many reduced ice days over continental shelf waters per year during 2008–2011” in southern Beaufort than Chukchi. And reduced ice cover can limit access to prey, the authors explain.

The Chukchi is an especially productive sea in terms of prey for polar bears. This may explain why the bears in this region haven’t succumbed to the perils of global warming as quickly as their neighbors, Steven C. Amstrup, chief scientist at Polar Bear International, told us by email. Also an adjunct professor at the University of Wyoming, Amstrup led polar bear research at the USGS for 30 years until 2010. With continued sea ice loss, he says, the Chukchi polar bears may follow in the footsteps of the southern Beaufort counterparts.

In fact, a 2010 USGS report projects “the shelf waters of the Chukchi Sea will be ice-free for at least 3 months (August–October) by mid-century. By the end of the century, and with somewhat less agreement among models, the Chukchi Sea shelf could be ice free (or nearly ice free) for as many as 4–5 months.” For comparison, a 2007 study published in the Annals of Glaciology by researchers at the University of Colorado’s National Snow and Ice Data Center found that from 1979-2000, on average, no months were left entirely without ice cover in the Chukchi Sea.

Rode, the lead author on the paper Murkowski’s office pointed us to, came to similar conclusions about the Chukchi population when she was interviewed by National Geographic about her study back in 2013.

She said: “The results of this study do not negate that sea ice loss remains a significant threat to polar bears, in the Chukchi Sea or elsewhere. … The rate and extent of sea ice loss that is projected for the Chukchi Sea, and for the Arctic as a whole, will require bears to change their behavior and potentially their ecology in ways that we have not yet seen.”

According to a 2015 PLOS ONE study by Rode and others, these behavioral changes are already occurring. The team found that Chukchi bears spent more time on land in recent years compared with the 1980s and 1990s. Spending time in land versus sea ice habitats has the “potential to increase nutritional stress and human-polar bear interactions,” the authors wrote. With continued sea ice loss, they predict this trend will only continue.

Threatened and Vulnerable

Declines in the population size and condition of Alaskan polar bears, among other factors, led the Department of the Interior to list the species as “threatened” under the Endangered Species Act. The ESA defines a “threatened species” as “any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.”

Other organizations, like NatureServe, a spin-off organization of The Nature Conservancy, also assessed the global status of polar bears as “vulnerable.” Its definition for this status is: “At moderate risk of extinction or elimination due to a restricted range, relatively few populations, recent and widespread declines, or other factors.”

Likewise, the International Union for Conservation of Nature lists polar bears globally as “vulnerable,” which it defines as “considered to be facing a high risk of extinction in the wild.”

In sum, Alaska’s polar bear populations are far from “strong and healthy,” as Murkowski claimed.

Editor’s Note: SciCheck is made possible by a grant from the Stanton Foundation.