From Skeptical Science and many other sources:

In conclusion, the reason polar bears have been classed as threatened comes from the impacts of future climate change on the bears’ habitat. Current analysis of subpopulations where data is sufficient clearly shows that those subpopulations are mainly in decline. Further habitat degradation will increase the threats to polar bears.

However, Susan Crockford is frequently named as collecting evidence for the claim that polar bears are doing well, despite a reduction in sea ice. Crockford is adjunct professor at the University of Victoria, Canada. For example, from her blog, Polar bears have not been harmed by sea ice declines:

Polar bear numbers overall have increased, despite the appearance of a ‘stable’ global population since 2001 and significant declines in Arctic sea ice coverage in summer

These claims appear to be well-sourced with links to research, from blog posts such as this one and this one. Blog posts themselves are, of course, not peer-reviewed, but it does appear to contain a lot of links to peer reviewed science.

Do the claims by Susan Crockford and others make sense? Is there substantial evidence to support the claim that polar bears are doing well despite a decline in sea ice? Or is the evidence solid that sea ice decline does substantially theaten the survival of polar bears?

For reference, IPCC AR5 WG2, Section (PDF, 7.0 MiB, 46 pages) states that projected extinction of polar bears is unlikely, so I'm not entirely sure to what extent the claims by Susan Crockford are in disagreement with scientific consensus as collected by IPCC, which is surprisingly short on polar bears.

  • I read a story on this somewhere. Instead of staying on the sea ice and eating seals, the polar bears return to land earlier in the year and eat nesting birds. The numbers of the birds have ballooned because of climate change in their winter habitat in the southern US.
    – GEdgar
    Mar 3 '15 at 16:35
  • 1
    @gerrit "the claim ultimately challenged here is the one that polar bears are threatened due to climate change." ... I think if that is the claim it should be reflected in the question. It seems to me substantially different than a question about polar bears' current status and recent population trends. Mar 3 '15 at 18:01
  • 1
    @Gerrit blog post on the subject here carbonbrief.org/blog/2015/03/… . I haven't read it, but I noticed it mentioned on twitter and remembered this question. Hope it has some useful info. Mar 5 '15 at 8:07
  • 1
    @DikranMarsupial Interesting blog post. I read that (1) Apart from Western Hudson Bay area, few areas have been sufficiently studied (2) it's important not to draw conclusions about polar bears as a species from a single population, and (3) the IUCN designated polar bears as "vulnerable", meaning the global population has declined by more than 30 per cent in 40 years. Could it be that both Crockford and IUCN extrapolate from too little data? But then again, of course, even a small probability of a serious decline implies a large risk, warranting the IUCN vulnerable status.
    – gerrit
    Mar 5 '15 at 16:34
  • 1
    "which is surprisingly short on polar bears" - we need more polar bears to become climate scientists! Sep 23 '15 at 22:33

We don't really know.

Despite the claims of a population boom, there is no definitive evidence to know how many polar bears there were "to begin with." One can't scientifically determine an end result with a variable starting point.

Polar Bears International asked Dr. Steven C. Amstrup, USGS polar bear project leader for 30 years the following question:

Q: Why all the fuss about polar bears? Aren't their populations increasing: in fact, booming?

A: One of the most frequent myths we hear about polar bears is that their numbers are increasing and have, in fact, more than doubled over the past thirty years. Tales about how many polar bears there used to be (with claims as low as 5,000 in the 1960s) are undocumented, but cited over and over again. Yet no one I know can come up with a legitimate source for these numbers.

PBI's official statement regarding a polar bear population boom:

A persistent myth to the contrary, polar bear numbers are NOT increasing.

An excellent article, by Peter Dykstra, in the Summer 2008 edition of Society of Environmental Journalists starts documenting all of the unfounded claims:

  • In a May 20 Los Angeles Times opinion piece, Jonah Goldberg took a whack at what he sees as quasi-religious overtones to conservation. Part of his backup? "Never mind that polar bears are in fact thriving — their numbers have quadrupled in the last 50 years."
  • James Taylor of the Heartland Institute cited a London Daily Telegraph article that "confirmed the ongoing polar bear population explosion" in a Sept 11, 2007, blog.
  • But the March 9, 2007, story that Taylor referenced actually makes no mention of global bear populations — quoting one scientist as observing strong growth in one local population, in Davis Strait; and another scientist reporting global warming-related declines in the local population in Hudson's Bay.
  • Taylor adds a new number into the mix from a March 26, 2008, posting at the Heartland site: "The global polar bear population has doubled since 1970, despite legal polar bear hunting."
  • A May 12 New York Post op-ed piece by S.T. Karnick introduces still another number — this time with a source:

    "The world polar-bear population is at a modern high — and growing. Mitch Taylor, a polar-bear biologist with Canada's Federal Provincial Polar Bear Technical Committee, notes that the bears now number about 24,000 — up about 40 percent from 1974, when fears arose about the bear's ability to survive overhunting by Canadian Eskimos and aboriginals."

  • From James Delingpole, a Times of London blogger, similar numbers, but different dates. And no source. "In 1950, let us not forget, there were about 5,000 polar bears. Now there are 25,000."

The article first extrapolates origins of the 5,000 number. Bjorn Lomborg's 2007 book, Cool It: The Skeptical Environmentalist's Guide to Global Warming." The book said, there were about 5,000. What was the footnote? "Krauss, 2006."

Clifford Krauss, a reporter for The New York Times, who wrote on May 27, 2006, about the conflict between polar bear protectors and trophy hunters: "Other experts see a healthier population. They note that there are more than 20,000 polar bears roaming the Arctic, compared to as few as 5,000 40 years ago." But he couldn't recall his source. He just said that number is widley accepted.

As we all know, Argumentum Ad Populum is a logical fallacy.

More commentary from Dr. Amstrup:

"How many bears were around then, we don't really know because the only studies of bears at that time were in their very early stages — people were just beginning to figure out how we might study animals scattered over the whole Arctic in difficult logistical situations. Some estimated that world population might have been as small as 5000 bears, but this was nothing more than a WAG. The scientific ability to estimate the sizes of polar bear populations has increased dramatically in recent years."

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .