Tag Archives: Southern Beaufort

Polar bear researchers knew S Beaufort population continued to increase up to 2012

Why did the Southern Beaufort polar bear population survey stop in 2010? It’s clear that the recently-published and widely-hyped new study stopped before the population rebound from a known decline was complete.

USFWS 2013-2014 PB News_cover_PolarBearScience

The researchers of the recently-published paper knew before starting their mark-recapture study in 2007 that the population decline had taken place. They also knew why the numbers dropped and that previous declines, caused by similar conditions, had been followed by a full recovery.

Did they really think a full recovery in population numbers was possible in only three four years, when cubs born in 2007 would not yet have been old enough to reproduce?

In fact, a US Fish and Wildlife Service (USFWS) fall survey of Southern Beaufort polar bears in 2012 found numbers were higher than they had been in a decade.
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S Beaufort polar bears largely recovered from known 2004-2006 decline, says new study

A bit more good news about polar bear populations, this time from an abundance study in the Southern Beaufort Sea. A paper released yesterday showed a 25-50% decline in population size took place between 2004 and 2006 (larger than previously calculated). However, by 2010 the population had rebounded substantially (although not to previous levels).

All the media headlines (e.g. The Guardian) have followed the press release lead and focused on the extent of the decline. However, it’s the recovery portion of the study that’s the real news, as it’s based on new data. Such a recovery is similar to one documented in the late 1970s after a significant decline occurred in 1974-1976 that was caused by thick spring ice conditions.

Polar bear with collar and tag_USGS_labeled

The title of the new paper by Jeffery Bromaghin and a string of polar bear biologists and modeling specialists (including all the big guns: Stirling, Derocher, Regehr, and Amstrup) is “Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline.” However, the study did not find any correlation of population decline with ice conditions. They did not find any correlation with ice conditions because they did not include spring ice thickness in their models – they only considered summer ice conditions.

I find this very odd, since previous instances of this phenomenon, which have occurred every 10 years or so since the 1960s, have all been associated with thick spring ice conditions (the 1974-76 and 2004-2006 events were the worst). [Another incident may have occurred this spring (April 2014) but has not been confirmed].

Whoever wrote the press release for this paper tried hard to suggest the cause of the 2004-2006 event might have been “thin” winter ice caused by global warming that was later deformed into thick spring ice, an absurd excuse that has been tried before (discussed here). If so, what caused the 1974-1976 event?

It seems rather unscientific as well as implausible to even try to blame this recent phenomenon on global warming. However, neither the authors of the paper or the press release writers seemed to want to admit that 2-3 years of thick ice development in the Southern Beaufort could have been the cause of the population decline in 2004 (as for all of the previous events). No, that wouldn’t do, not in the age of global warming.

So, we are left with this equally absurd conclusion from the author:

The low survival may have been caused by a combination of factors that could be difficult to unravel,” said Bromaghin, “and why survival improved at the end of the study is unknown.

I’ve summarized the paper to the best of my understanding (there was a lot of model-speak to wade through), leaving out the prophesies of extinction, which in my opinion don’t add anything.

UPDATE November 19, 2014: Don’t miss my follow-up post, with some startling new information, Polar bear researchers knew S. Beaufort population continued to increase up to 2012
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Tracking polar bears in the Beaufort Sea – October 2014 map shows most ice since 2010

Here is the October 2014 follow-up to my post on the July 2013 track map for female polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice.”

See that post for methods and other background on this topic, and some track maps from 2012 (also available at the USGS website here). The USGS track map for October 2014 is copied below (Fig. 1).

For the end of October, there was more ice in the Southern Beaufort this year than there has been since 2010.

Eight bears (all females) were on the ice and four were onshore. Only six of the eight on-ice bears were actually in the Southern Beaufort – the other two were in the Chukchi Sea (west of Point Lay, see discussion here).

Note that the recent boundary change between the Southern and Northern Beaufort subpopulations (the US/Canada boundary of the Southern Beaufort), reported here, has not addressed the fact that many western “Southern Beaufort” bears move into the Chukchi Sea. Continue reading

Status of Canadian polar bear populations has been changed – more good news

According to maps dated June 2014, Environment Canada (EC) has changed the trend status of several Canadian subpopulations — without any announcement or publicly-available documents explaining the basis of the changes.

Figure 3. "Series of Circumpolar Polar Bear Subpopulation and Status Trend Maps 2010, 2013 & 2014" Note the asterisk below the 2014 map, which is dated "June 2014" and is different in its status assessment from the one released in February 2013 by the PBSG. Original here.

Figure 1. Environment Canada’s “Map 4: Series of Circumpolar Polar Bear Subpopulation and Status Trend Maps 2010, 2013 & 2014.” Original here.

And would it surprise you to learn that virtually all of these status changes reveal more good news about polar bears?
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Beaufort Sea polar bear subpopulation boundary has been changed

Environment Canada recently posted a set of maps on its website that show it has moved the boundary between the polar bear subpopulation it shares with the USA — without a word to the media or a note anywhere.

EC S_N Beaufort boundary change Sept 8 2014_cropped PolarBearScience

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Tracking polar bears in the Beaufort Sea – September 2014 map

Here is the September 2014 follow-up to my post on the July 2013 track map for female polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice.”

See that post for methods and other background on this topic, and some track maps from 2012 (also available at the USGS website here).

The USGS track map for September 2014 is copied below (Fig. 1).

At the end of September, with sea ice starting to rebuild, it appears there were 8 bears on the ice and three on land.

The situation for September was not very much different from August, except that two of the 11 bears (up from one) were on the ice in the Chukchi Sea in September, a phenomenon that was recently acknowledged to have affected the last population estimate for the Southern Beaufort subpopulation.

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Tracking polar bears in the Beaufort Sea – August 2014 map

Here is the August 2014 follow-up to my post on the July 2013 track map for female polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice.”

See that post for methods and other background on this topic, and some track maps from 2012 (also available at the USGS website here).

The USGS track map for August 2014 is copied below (Fig. 1).

Compare this to July’s map (Fig. 4). The 20 bears from May (down to 13 in June) are now down to 11. All seven of the bears outfitted with glue-on satellite transmitters in April [either males or subadult animals] have either moved out of the area or their tags have fallen off or stopped transmitting. This means that all of the bears shown on the maps below are females.

At the end of August, nearing the minimum extent of ice for this year, seven bears were on the ice and only four were on land.
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