Tag Archives: Barents Sea

Svalbard polar bear paper falsely assumes that loss of genetic diversity has negative consequences

A new paper published today deals with an animal conservation issue I’ve addressed twice before: the theoretical assumption that loss of genetic diversity must be detrimental to species survival despite there being little evidence that this has been the case in real life. For this new study, the authors carried out some complicated measuring of genetic diversity loss and inbreeding amongst and between Svalbard region polar bear populations between 1995 and 2016 (see map below), and then modelled what this could lead to in 100 generations (1210 years), with the over-anxious hand-wringing we’ve all come to expect from such prophesies. As far as I can see, it’s all meaningless number-crunching without relevance to the real world of polar bears.

To support their claim of harm from loss of genetic diversity, the authors of this paper (Maduna et al. 2021) cite four theoretical papers that assume as fact that loss of genetic diversity is harmful but not the evidence to back up the claim. They apparently never bothered to look at species that have actually suffered dramatic loss of genetic diversity. Northern elephant seals, for example, reduced to 20-30 animals more than 100 years ago, have rebounded to a population of about 170,000 with extremely low genetic diversity but no apparent health or survival repercussions. Similar genetic bottlenecks and recoveries have been documented in Guadalupe fur seals, San Nicolas Island foxes, mouflon sheep, and North Atlantic right whales (among others), which I discussed in detail here (with references). I discussed the issue again in regards to a similar polar bear ‘genetic diversity’ paper in 2016.

Conspicuous by its absence in this new publication is a citation of the recent paper that revealed the body condition of female Svalbard polar bears had increased significantly between 2004 and 2017 despite a pronounced decline in summer and winter sea ice extent (Lippold et al. 2019: 988). Nor did the paper cite data collected by the Norwegian Polar Institute that show the body condition of adult males in Svalbard has not changed since 1993 or that population numbers have not declined. Instead, the authors mention only that reduced numbers of pregnant females have reached traditional denning areas due to lack of ice and that bears have spent less time feeding at glacier fronts than they used to do (Maduna et al. 2021: 2), as if the only polar bear data available in relation to sea ice decline was negative.

Figure 1 from Maduna et al. 2021

Population bottlenecks during the Last Glacial Maximum when suitable habitat was scarce and another in the late 1800s/early 1900s due to wanton overhunting left polar bears with remarkably low genetic diversity but no apparent ill-effects to their overall heath. Oddly, this recent work by Maduna and colleagues assumes without evidence that a bit less genetic diversity could be devastating to Svalbard bears more than 1000 years from now. While the media expectedly promote this as scary new evidence of what climate change has wrought (here and here), I am not impressed.

This is conservation biology done WWF-style: loss of genetic diversity sounds bad to people who don’t know better, but real-world evidence shows it isn’t.

References

Lippold, A., Bourgeon, S., Aars, J., Andersen, M., Polder, A., Lyche, J.L., Bytingsvik, J., Jenssen, B.M., Derocher, A.E., Welker, J.M. and Routti, H. 2019. Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition. Environmental Science and Technology 53(2):984-995. https://pubs.acs.org/doi/10.1021/acs.est.8b05416

Maduna, S. N., Aars, J., Fløystad, I., Klütsch, C. F. C., Zeyl Fiskebeck, E. M. L., Wiig, Ø. et al. 2021. Sea ice reduction drives genetic differentiation among Barents Sea polar bears. Proceedings of the Royals Society B  288 (1958): 20211741. https://doi.org/10.1098/rspb.2021.1741 OPEN ACCESS

Barents Sea polar bears thriving despite huge summer ice loss: spring research results are in

After being locked out last year, fieldwork monitoring polar bears in the Svalbard region of the Barents Sea resumed this spring. The results show that despite having to deal with the most extreme loss of summer sea ice in the entire Arctic, polar bears in this region continue to thrive. These facts show no hint of that impending catastrophic decline in population size we keep hearing is just around the corner. No tipping point here.

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More polar bear catastrophe hype: bears use four times more energy than expected

Last week (24 February 2021), The Guardian was promoting a study that claims polar bears now use four times more energy than expected to survive because of ‘major ice loss’ in the Arctic, as a way of suggesting that the animals are already on their way to extinction.

But like many papers of this type, this study by Anthony Pagano and Terri Williams (Pagano and Williams 2021) is yet another model describing what biologists think may be happening based on experimental data collected from individual bears, not a conclusion based on evidence collected from subpopulations with the worst amounts of ice loss.

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Polar bear sea ice habitat highs and lows in early February

Sea ice across the Arctic in the first week of February is a mix of highs and lows. Bering Sea is back up to almost normal coverage, as is the Barents Sea. However, ice coverage on the East Coast of Canada is the lowest its been in four decades. This is not yet a worry for polar bears because harp seals don’t pup until mid-March in this region so there is at least four weeks of potential ice growth that can happen before the seals are forced to pup on much reduced ice – where polar bears are sure to find them.


Here is a close-up look at sea ice conditions by region at the edges of the Arctic. Continue reading

Some surprises in polar bear sea ice habitat at mid-October 2020

Arctic sea ice has been growing steadily since the minimum extent was reached a month ago, with shorefast ice now developing along the Russian and Alaskan coastlines as ice cover expands in the Central Canadian Arctic. So while it’s true that the main pack of Arctic ice is far from the Russian shoreline, rapidly developing shorefast ice will allow bears to begin hunting seals long before ice in the central Arctic Basin reaches the Siberian shore, as they do in Western and Southern Hudson Bay every fall.

Cropped sea ice extent at 15 October 2020 (Day 289), NSIDC Masie.

And speaking of Western Hudson Bay, it’s a very slow season around Churchill for problem polar bears (photo below) – the quietest mid-October for the Polar Bear Alert Program in the last five years and perhaps the quietest in decades (which I could say for sure if I had the records but I do not).

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Still pack ice around Bear Island in the Barents Sea on 15 May: last time was 2003

It’s very open drift ice (1-4/10th concentration) but still: Bear Island (Bjørnøya) in the southern Barents Sea was still surrounded by pack ice at 15 May 2020. As far as I can tell from the Norwegian Ice Service archived ice charts, this hasn’t happened since 2003.

Svalbard ice extent 2020 May 15_NIS

And last week, the island was surrounded by heavy drift ice, which hadn’t happened on 8 May since 1977.

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New Paper: Body condition of Barents Sea polar bears increased since 2004 despite sea ice loss

A recent paper that attempted to correlate pollution levels and body condition in Barents Sea polar bears reports it found body condition of female bears had increased between 2004 and 2017 despite a pronounced decline in summer and winter sea ice extent.

Svalbard polar bear Jon Aars_Norsk Polarinstitutt

“Unexpectedly, body condition of female polar bears from the Barents Sea has increased after 2005, although sea ice has retreated by ∼50% since the late 1990s in the area, and the length of the ice-free season has increased by over 20 weeks between 1979 and 2013. These changes are also accompanied by winter sea ice retreat that is especially pronounced in the Barents Sea compared to other Arctic areas” [Lippold et al. 2019:988]

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Svalbard at end of April again has 6th-7th highest sea ice extent & a lot of very thick ice

For the second time this month, sea ice around Svalbard Norway was the 6th or 7th highest since records began in the late 1960s. Pack ice at the end of April still surrounds Bear Island (Bjørnøya) at the southern end of the archipelago, which is a rare occurrence at this date. These conditions document a recurrent pattern of high ice extent and especially extreme ice thickness in the Barents Sea since last summer.

Bear island 8 March 2019_first bear seen since 2011_Bjørnøya Meteorological Station photo SVALBARDPOSTEN

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Highest Svalbard sea ice since 1988 with Bear Island in the south surrounded

From 3-7 April this year, sea ice around Svalbard Norway has been the highest since 1988, but only 6th or 7th highest since records began in the 1970s. Pack ice is year surrounds Bear Island (Bjørnøya) at the southern end of the archipelago for the first time since 2009 at this date, and continues the pattern of high extent and thickness of ice in the Barents Sea since last summer.

Bear island 8 March 2019_first bear seen since 2011_Bjørnøya Meteorological Station photo SVALBARDPOSTEN

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Svalbard Norway now has more polar bear habitat than it did two decades ago

Sea ice around Svalbard, Norway at the end of February 2020 is way above average, as the graph below shows – with more polar bear habitat now than there has been in two decades.

Svalbard ice extent 2020 Feb 28 graph_NIS

Some comparison charts below show that the graph above includes some very high ice years in the 1980s (reaching that dotted line above the mean) for which only global charts are available.

However, contrary to suggestions that more Svalbard ice is better for polar bears, there is no evidence that low extent of sea ice habitat in winter or summer over the last two decades harmed polar bear health, reproductive performance, or abundance. In fact, polar bear numbers in 2015 were 42% higher than they were in 2004 (although not a significant increase, statistically speaking) and most bears were found to be in excellent condition.

Svalbard polar bear_Aars August 2015-NP058930_press release

This suggests a return to more extensive ice to the Svalbard region in winter will have little impact on the health of the entire Barents Sea subpopulation, although it might change where pregnant females are able to make their maternity dens if ice forms early enough in the fall. In other words, the population should continue to grow as it has been doing since the bears were protected by international treaty in 1973.

UPDATE 3 March 2020: According to 28 February tweet by the Norwegian Ice Service, which I just saw today, “the last time there was this much sea ice around Svalbard on this day of the year [28 February] was 2004“. Somehow, I missed 2004 when I was looking through the archive, so I have modified the text below accordingly; see the 2004 chart below and here.

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