Svalbard polar bear data for spring 2022, low June ice unlikely to affect health or survival

Sea ice around Svalbard, Norway has receded dramatically over the last few weeks and is now at levels similar to 2018 and 2006. But the data are in for the 2022 spring season and they show the bears are still thriving.

While polar bear specialists insist that summer sea ice is essential for polar bear survival, the bears around Svalbard did not die out in 2018 when June ice was lower than this year and even though ice cover has taken a nose-dive early in the season in 2022, there is no reason to assume this means dire consequences for polar bears. These bears continue to thrive despite markedly reduced summer sea ice and even reduced winter ice, because it’s spring ice that matters (Crockford 2017).

The graph above shows 2022 didn’t have the lowest ice coverage on 25 June in recent times and a tweet report by the Norwegian Ice Service (below) stated that the lowest coverage on that date was reached in 2018 (closely followed by 2006):

Comparing sea ice charts by year

Polar bear health data to 2022

From the Norwegian researchers who moniter polar bears that persist around Svalbard, here are the latest data, from spring 2022:

Litter size was slightly below average this year but note how high it was in 2019 (‘2.0’), the year after what should have been a devastating year for these bears after such low summer ice in 2018 (note that a point for 2020 is missing due to pandemic restrictions on field research). Overall there is a slight but statistically significant declining trend since 1993:

The graph below shows that the number of females with cubs-of-the-year (blue dots) and one-year-old cubs (red dots) were both up slightly in 2022, although overall, neither metric had a significant trend (declining or increasing) over time:

Body condition of adult male bears shown below was down a bit but not significantly, and 2019 saw bears in the best condition since 1995 (2020 data is missing). The median of -0.29 for this year was slightly better than 2006 (which had a median of -0.355).

Ironically, 2003 was the worst year for male body condition at -0.415, a year when lack of summer sea ice was not an issue. A sea ice charts for mid-June in the Barents Sea that year (below) shows sea ice was still abundant after an extensive ice cover that winter, the highest it had been since 1999 (King et al. 2017).

Body condition of females is not presented in the annual records posted by Norwegian researchers but a 2019 study showed female bears have also been thriving in recent years.

“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]

Sea ice condition at mid-May 2022

Mid-May is close to the end of the field season in the Barents Sea (and also the end of the intense feeding of polar bears on newborn seals as well as the end of the mating season), so these ice conditions are the most pertinent to recent polar bear body health metrics:

This year, the ice had retreated dramatically from the east coast of Svalbard by early June (below) but this no longer really mattered to polar bears: they had a choice to remain with the sea ice as it retreated north or spend the summer onshore in the Svalbard archipelago (either option offer few feeding opportunities).

References

Crockford, S.J. 2017. Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus). PeerJ Preprints 19 January 2017. Doi: 10.7287/peerj.preprints.2737v1 Open access. https://peerj.com/preprints/2737/

King, J., Spreen, G., Gerland, S., et al. 2017. Sea-ice thickness from field measurements in the northwestern Barents Sea. Journal of Geophysical Research Oceans 122:1497–1512. doi:10.1002/2016JC012199

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.

via polarbearscience

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June 26, 2022 at 08:44PM

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