Tag Archives: threatened species

Low genetic diversity will not make polar bears more vulnerable to extinction

You’ve probably heard the argument: animal populations that have been through a major decline in numbers often have such low genetic diversity that they are extremely vulnerable to subsequent extinction.

Photo credit USGS

Photo credit USGS

In an interview in late March regarding a new genetic paper on polar bear evolution (by Matt Cronin and colleagues), polar bear biologist and Polar Bears International spokesperson Steve Amstrup made a ridiculous statement: that polar bears have never experienced a rate of warming like they’ve seen over the last 30 years. I countered that easily here.

In that same interview about the Cronin et al. paper, fellow geneticist Charlotte Lindqvist offered an outdated argument against future polar bear survival that is as easy to refute as Amstrup’s “unprecedented rate of warming” nonsense.

I didn’t have time to deal with it back in April [where has the time gone?] but want to get back to it now because it’s important: there is lots of evidence to support my contention that polar bears are not more vulnerable to extinction just because they have low genetic diversity.
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Earth to Newsweek: polar bear populations have not been on the decline since 2008

A recent Newsweek story about the US Navy having no “rules of engagement” to deal with polar bear encounters leads with alarmist misinformation.

Photo credit Cmdr. Christy Hagen/U.S. Navy

Photo credit Cmdr. Christy Hagen/U.S. Navy

Author Max Strasser (April 30, 2013), in his recent article in Newsweek (As the World Warms, Navy Strategists Plan for an Arctic Rush”) [h/t D. V]

Approximately 25,000 polar bears live in and around the Arctic Circle. Climate change has put the majestic ursines, a longtime favorite of children’s books and Christmas cards, in peril. In 2008, the United States listed them as a “threatened species” under the Endangered Species Act, and populations have been on the decline since then.”

Sigh. Not so Max, totally not so.

Global polar bear numbers have been stable for the last 30 years, as the graphs below show. The proposed ‘threat’ to polar bears is a future decline in sea ice predicted by computer models. The future, Max, is not now.

Polar bear populations are currently doing very well (see my post on the most recent status update report here). On top of that, note that the bears are well distributed throughout available Arctic habitat — one of the accepted hallmarks of a healthy species.

Figure 1. Upper graph uses totals reported in PBSG status tables, with min/max; Lower graph uses the same figures, but adds back in the so-called "inaccurate" estimates dropped 2005-2013. The 1960 figure * is a ballpark estimate. See previous post here.

Figure 1. Upper graph uses totals reported in PBSG status tables, with min/max; Lower graph uses the same figures, but adds back in the so-called “inaccurate” estimates dropped 2005-2013. The 1960 figure * is a ballpark estimate.
See previous post here.

OK, with that error corrected, back to the point of the Newsweek story…

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Chukchi/Bering Sea ringed seals doing better despite declines in ice and snow: new study

Ringed seal pup in snow cave

Previously, I highlighted new research results that showed, contrary to expectations, polar bears in the Chukchi Sea subpopulation are doing better – despite declines in extent of September sea ice – since the 1970s. So it might not come as much of a surprise to find that the same is true for the primary prey of polar bears in the Chukchi and Bering Seas, Arctic ringed seals (Phoca hispida hispida).

Surprisingly, less than 6 months after Arctic ringed seals were placed on the American list of “threatened” species (under the ESA, see previous post here), actual research in Alaska has shown that declines in sea ice have proven better for ringed seals, not worse.

At a presentation given at the Lowell Wakefield Fisheries Symposium in March (Anchorage, Alaska) [program and links to pdfs here] Justin Crawford, a biologist with the Alaska Department of Fish and Game (ADF&G) presented the results of ringed seal research conducted by himself and fellow ADF&G biologist Lori Quakenbush in the Chukchi and Bering Seas (posted online by the event organizers, see references below).

As for polar bears, the Crawford and Quakenbush presentation provides some very interesting details on the status of Chukchi and Bering Sea ringed seals over the last 40 years, and contains some mighty “inconvenient” conclusions that should raise some eyebrows.

I’ve summarized these details and conclusions below in point form, with a map.
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