Category Archives: Population

Environment Canada maps of polar bear population and status assessments 2018

Just out (6 June 2018) — new population assessment and status maps of the 19 polar bear subpopulations according to Environment Canada. Contrary to the map presented at the Range State meeting in February 2018 (pdf here), these maps show Western Hudson Bay and Southern Hudson Bay (along with the Southern Beaufort) as “likely declined.” A new category has been added for the Barents Sea: it’s considered “data deficient/uncertain,” but a population estimate of 2,001-3,000 has been provided.

No press release or other notice regarding the availability of these new maps was issued, as far as I know: I came across them by accident while looking for something else.

Global pb status and population map EC 2018

Global map above, more below, including a comparative map that shows 2010, 2014, and 2018 together. I will update the two recent posts of mine (here and here) that used the February Range State map with the information that more recently revised maps are now available.

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Critical evidence on W Hudson Bay polar bears still not published after 25 years

Polar bear researchers have been doing capture/recapture studies in Western Hudson Bay for decades yet most of the data claimed to be critical for assessing effects of human-caused global warming on this species have not been published. I raised this point in one of my early blog posts (27 Sept 2012) but the situation has not changed in 6 years. Here’s an update.

Derocher in the field in WH_CBC story 2016

From CBC story 14 Sept 2016.

Years ago now, in an oft-cited paper, Stirling and Derocher (2012) claimed to summarize the evidence that climate warming was negatively impacting polar bear health and survival. Several life history parameters were considered crucial, particularly body condition.

Despite almost a dozen papers (and perhaps more) on various aspects of WH polar bear health and life history studies based on capture/recapture data published since 2004  (e.g. Castro de la Guardia 2017; Lunn et al. 2016; Pilfold et al. 2017), none have reported the body condition data that supposedly support the claim that sea ice loss is having a severe impact — and the same is true for litter size, proportion of independent yearlings, and cub survival.1

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Southern Hudson Bay polar bear region shows slight decline after decades of low sea ice

A newly-published paper by Martyn Obbard and colleagues in the journal Arctic Science claims a 17% decline in abundance of polar bears in the Southern Hudson Bay region after years of reduced sea ice and declining body condition (Obbard et al. 2018). The decline in numbers was not statistically significant but an additional statistical analysis (“Monte Carlo simulation”) not applied to any other estimate in recent years suggested the decline could be real, so a real decline is what was reported to the press.

James Bay polar bear_ministry of Ontario_Walton photo

Only one Canadian Press story has so far been circulated amongst outlets in the media (published hours after the paper appeared online, not at the same time), suggesting there was no press release issued for this study. Odd, that — especially if the decline is as real and significant as the authors suggest.

While no evidence was provided for a correlation of this decline in numbers to recent (2012-2016) sea ice decline, previous evidence from the region (Obbard et al. 2016) showed a decline in body condition was correlated only with much later than usual freeze-up, a situation that did not occur from 2012 to 2015 (freeze-up was late in the fall of 2016 but occurred months after the Obbard et al. (2018) survey was completed).

Moreover, the paper reports that a decline in survival of yearling cubs (from 12% of the population in 2011 to 5% in 2016) was not associated with especially poor sea ice conditions in spring. We are likely to see a follow-up paper next year reporting the body condition and sea ice data from this study (as for the previous survey: Obbard et al. 2015, 2016), but there is no suggestion in this paper that body condition declined further from 2011/2012 levels or that sea ice conditions deteriorated markedly enough after 2012 to precipitate a population decline.

UPDATE 11 June 2018: See below, more recent versions of population and status assessment maps has been issued by Environment Canada that conclude Southern Hudson Bay is “likely declined.”

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Activist laments ESA listing of polar bears in 2008 failed to achieve her political goals

The activist lawyer primarily responsible for polar bears being listed as ‘threatened’ on the US Endangered Species List (ESA) in 2008 is frustrated that those efforts have not generated her preferred political action. Kassie Siegel also claims in another 10 years it will be too late to save polar bears from extinction — despite clear evidence to the contrary.

Walking bear_129029633_web size

In an emotional rant over at The Hill with a predictably hysterical headline, Siegel perhaps reveals more than she should about her motivation (“Keeping fossil fuels in the ground is the only way to save polar bears ravaged by climate change,” 26 May 2018).

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Status of Canadian polar bears updated map from Environment Canada

During a meeting of polar bear range states (Canada, Russia, Greenland, Norway, and the USA) in late January 2018 to discuss conservation issues, Canada — home to ~2/3 of the world’s polar bears — included in its presentation an updated population status and trend map approved by the Polar Bear Technical Committee in its presentation. This 2017 map replaces one from 2014 but is not yet available on the Environment Canada website.

Lunn et al 2016 EA cover image WH bear

UPDATE 11 June 2018: More recent versions of population and status assessment maps, published by Environment Canada 6 June 2018, conclude Southern Hudson Bay and Western Hudson Bay subpopulations have “likely declined.” See 11 June post here for more details and copies of the maps.

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Polar bear numbers, margins of error, & consequences for conservation status

Large margins of error in polar bear population estimates means the conservation status threshold of a 30% decline (real or predicted) used by the US Endangered Species Act and the IUCN Red List is probably not valid for this species.

Polar_Bear_Biologist_USFWS_working_with_a_Bear_Oct 24 2001 Amstrup photo

Several recent subpopulation estimates have shown an increase between one estimate and another of greater than 30% yet deemed not to be statistically significant due to large margins of error. How can such estimates be used to assess whether population numbers have declined enough to warrant IUCN Red List or ESA protection?

What do polar bear population numbers mean for conservation status, if anything?

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Polar bear specialist Mitch Taylor on accountability in polar bear science

Polar bear specialist Mitch Taylor emailed me and others his response to the New York Times article that appeared Tuesday (10 April) about the Harvey et al. (2018) BioScience paper attacking my scientific integrity. Here it is in full, with his permission, and my comments. Don’t miss the footnote!

Mother with cubs Russia_shutterstock_71694292_web size

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