Dr. Susan Crockford
Canadian government scientists created headline news worldwide last week when they told the media that Western Hudson Bay polar bear numbers appeared to have declined by 27% between 2017 and 2021, based on a survey report that has not been made public. This is called ‘science by press release’. Its practice is rightfully considered unethical, as it is usually associated with “people promoting scientific ‘findings’ of questionable scientific merit who turn to the media for attention when they are unlikely to win the approval of the professional scientific community.”
Not surprisingly, all of the stories stated or implied a strong association between this purported population decline and lack of sea ice due to ‘climate change’. However, sea ice conditions have been particularly good over the last five years–for both freeze-up and breakup dates–calling into question how ‘lack of sea ice’ could possibly be to blame for the apparent decline.
Scientists cautioned a direct link between the population decline and sea ice loss in Hudson Bay wasn’t yet clear, as four of the past five years have seen moderately good ice conditions. Instead, they said, climate-caused changes in the local seal population might be driving bear numbers down.
For example, an Associated Press story published the day before (22 December 2022), picked up by many other outlets, did not include these critical pieces of information about recent good sea ice conditions and possible declines in seal abundance.
Without being able to check the actual government report for details (which is not a peer-reviewed document), there is not much more that I can say. Although several news stories claimed the report was recently released, it was not publicly available on the Nunavut Government website as of 28 December or anywhere else online that I could find. None of the news reports link to any such ‘available’ study, cited its title, or even linked to an official press release.
However, based on the Reuters story, it appears that the authors were unable to make a definitive link between sea ice loss and a decline in polar bear numbers in Western Hudson Bay, despite what they (or others) might have told the media.
What about ringed seals, their primary prey? Have ringed seal numbers declined over the 2017-2021 period, creating a lack of food for bears in Hudson Bay? If so, is there a clear correlation between declining ringed seal numbers and lack of sea ice, as implied by the Reuters statement quoted above?
The short answer is no. Studies on ringed seals in Hudson Bay indicate no definitive cause and effect between sea ice changes and seal health and survival (Ferguson et al. 2017, 2019, 2020), primarily because there has been no declining trend in sea ice coverage:
Our trend analysis of environmental variables indicated a strong warming pattern prior to 1999. Following this decisive shift, the region has demonstrated no warming trend. Still, the 2000 to 2016 body conditions trend was negative suggesting an overall decline in ringed seal body fat over this period. [Ferguson et al. 2020]
In other words, if there has been an actual decline in polar bear numbers, as the authors claim to have found, it is not clear by any means what is to blame. If some bears were not finding enough seals to eat over the last few years and have been starving to death, it is not at all clear why there were fewer seals available.
Bottom line: There are no data linking a critical lack of sea ice to poor health or abundance for either polar bears or their ringed seal prey in Western Hudson Bay between 2017 and 2021. Despite this, the authors of a government report on polar bear numbers that is not yet publicly available felt comfortable telling the media that lack of sea ice could be blamed for an apparent decline in polar bear abundance over the last five years, confirming earlier predictions that this is exactly what would happen because of human-caused global warming. I call this a perfect example of ‘science by press release‘, which researchers resort to only when they have findings of questionable scientific merit and a sensational narrative to push.
I’ll assess the actual report when it is made publicly available.
Ferguson, S.H., Young, B.G., Yurkowski, D.J., et al. 2017. Demographic, ecological, and physiological responses of ringed seals to an abrupt decline in sea ice availability. PeerJ 5:e2957. https://doi.org/10.7717/peerj.2957
Ferguson, S.H., Yurkowski, D.J., Young, B.G., et al. 2019. Do intraspecific life history patterns follow interspecific predictions? A test using latitudinal variation in ringed seals. Population Ecology 61(4):371-382. https://doi.org/10.1002/1438-390X.12008
Ferguson, S.H., Yurkowski, D.J., Young, B.G., et al. 2020. Comparing temporal patterns in body condition of ringed seals living within their core geographic range with those living at the edge. Ecography 43:1521-1535. https://doi.org/10.1111/ecog.04988