A ‘mass exodus’ of polar bears from Alaska to Russia has taken place, local residents claim

An article in a UK newspaper yesterday contains a claim made by local residents that polar bears which used to hang around Utqiagvik (formerly known as Barrow) in western Alaska, are ‘moving to Russia’ (i.e. the Chukchi Sea) in a ‘mass exodus’. It’s certainly possible but if so, it should come as a surprise to no one and is good news for polar bears.

If the allegation is upheld by scientific evidence, polar bears will not have been pushed out of Alaska by lack of summer sea ice (i.e. ‘forced to migrate’) but rather pulled into the Chukchi Sea by abundant food resources that did not exist when summer ice cover was more extensive. It’s a big difference and it speaks to the benefits of less summer sea ice that no one wants to discuss.

Moreover, moving temporarily to where conditions suit them best is what polar bears do all the time: it’s not a new phenomenon, it’s a prominent feature of their biology (Crockford 2019).

Chukchi Sea vs. Southern Beaufort Sea polar bear subpopulation boundaries, from Amstrup et al. 2005.

The article in question appeared yesterday in the UK Daily Telegraph (1 Jan 2020), “Polar bears forced to migrate from America to Russia because of climate change”. The piece oddly conflates a record high temperature on Boxing Day 2021 in Kodiak (located in the Gulf of Alaska, which is nowhere near the Beaufort Sea and well south of polar bear territory) with lack of summer sea ice much further north [my bold]:

After two days driving through thick snow on America’s most northerly tip, we had seen no sign of polar bears. The beasts, locals warned, are moving to Russia

“It wasn’t always like this,” said Herman Ahsoak, a whaling captain from Utqiagvik, Alaska, who was acting as a guide.

“Back in the late 1990s there were 127 here. I had never seen so many in my life. We had a dedicated patrol team to keep watch and protect the town.

“But when the sea ice really started to retreat, we stopped seeing them so often. I’m sure there is still a healthy population, but they have mostly moved on from here.”

In this part of America, where the average annual temperature has risen by 4.8°C in the last 50 years, one of the most visible signs of global warming is the mass exodus of polar bears.

Global warming has caused sea ice to melt, depriving bears of their homes and hunting grounds…

The problem is immediate: On Boxing Day, temperatures soared to a record 19.4C on the island of Kodiak – the highest December reading ever recorded in Alaska.

Polar bears, with their 42 razor sharp teeth, paws the size of dinner plates and 4 inches of fat under their black skin and white fur are some of the most resilient mammals on the planet. But scientists believe that climate change has driven them away.

Far to the west, on Russia’s Wrangel Island in the neighbouring Chukchi sea, the population has grown significantly, with scientists counting a record 747 bears in 2020, up from 589 in 2017.

The overall number of polar bears in the Chukchi sea has ballooned to 3,000 and they are described as being “in better condition, larger, and appeared to have higher reproductive rates than bears inhabiting the southern Beaufort Sea,” by Dr Karyn Rode, from the Alaska Science Centre.

“What is portrayed in the press and what is promoted by environmental groups creates a lot of stress because it is not an accurate picture,” said Dr Robert Suydam, a senior wildlife biologist for the North Slope Borough, in Utqiagvik.

“So frequently they are estimating that the populations in the Beaufort Sea have declined substantially but they are not taking into account how many bears have moved to other areas.

“Without a doubt, polar bears are struggling and will struggle with the change in ice. They have to adapt and they are. But unfortunately, some of these groups that are promoting that bears are in trouble aren’t giving the bears enough credit for how they can adjust to the change in environment.”

Because the Chukchi waters off Russia are so rich with food, polar bears appear to need less time on the ice.

“Bears can withstand having a shorter time out on the sea ice each year because when they are on the ice, there are plenty of seals to go around to recoup those losses to a point,” said Eric Regehr, a former biologist with the US Fish and Wildlife Service who now works at the University of Washington.

At issue here is the claimed ‘mass exodus’ of bears.

In fact, it’s been known for decades that most of the bears that visit Utqiagvik really belong to the Chukchi Sea subpopulation: virtually all of these visitors have always been Russian bears, not Alaskan (see below from Amstrup et al. 2005; see also Amstrup et al 2001).

Capture locations of Chukchi and Southern Beaufort Sea polar bears, from Amstrup et al. 2005.

In fact, movement of bears into and out of the Southern Beaufort at both ends has confounded efforts to get an accurate population size estimate (AC SWG 2018; Atwood et al. 2020; Bromaghin et al. 2015; Conn et al. 2021; Rehehr et al. 2018).

Moreover, very few Southern Beaufort or Chukchi Sea bears ever come to land at all: these are subpopulations where most bears remain on the sea ice year-round (Crockford 2018, 2019; Rode et al. 2015).

And while these folks blame lack of sea ice in the Southern Beaufort for driving the bears away, the author of the piece neglects to explicitly state the obvious alternative explanation (although he alludes to it): that abundant food in the Chukchi Sea in recent years caused by greater primary productivity during the longer ice-free seasons has made ice over Russian waters a more attractive place to live for polar bears (Frey et al. 2021; Rode et al. 2014, 2018).

It’s the back-handed way of presenting one of the great benefits of reduced summer sea ice in the Arctic that’s blamed on ‘climate change’ (Crockford 2021). Get used to it: this is something we will likely be seeing more of in the next few years as the predicted summer sea ice ‘decline’ remains stalled (see graph below from Meier et al. 2021).

If it’s indeed true that Chukchi Sea polar bears now seldom visit the area around Point Barrow because the bears have moved to Russia (which is not, by the way, mentioned by biologists in scientific papers as an explanation for the apparent decline in polar bears in the Southern Beaufort or the apparent increase in Chukchi Sea numbers), this resilience to changing conditions would be very much like the situation in the Barents Sea on the other side of the Arctic.

As I’ve discussed previously (with references), the many pregnant polar bear females that used to give birth in the Svalbard archipelago (managed by Norway) have largely shifted east to make their maternity dens on the sea ice or the islands around Franz Josef Land in Russia. However, those that have remained loyal to Norwegian waters are not struggling, but are thriving (Aars et al. 2017).

Quite simply, this flexibility in response to changing conditions in the Arctic has allowed the polar bear to be an evolutionarily successful species and not a symptom of climate change victimhood.

References

Aars, J., Marques,T.A, Lone, K., Anderson, M., Wiig, Ø., Fløystad, I.M.B., Hagen, S.B. and Buckland, S.T. 2017. The number and distribution of polar bears in the western Barents Sea. Polar Research 36:1. 1374125. doi:10.1080/17518369.2017.1374125

AC SWG 2018. Chukchi-Alaska polar bear population demographic parameter estimation. Eric Regehr, Scientific Working Group (SWG. Report of the Proceedings of the 10th meeting of the Russian-American Commission on Polar Bears, 27-28 July 2018), pg. 5. Published 30 July 2018. US Fish and Wildlife Service. https://www.fws.gov/alaska/fisheries/mmm/polarbear/bilateral.htm pdf here.

Amstrup, S. C., McDonald, T. L. and Stirling, I. 2001. Polar bears in the Beaufort Sea: A 30-year mark-recapture case history. Journal of Agricultural, Biological, and Environmental Statistics 6:221-234. http://link.springer.com/article/10.1198/108571101750524562

Amstrup, S.C., Durner, G. M., Stirling, I. and McDonald, T. L. 2005. Allocating harvests among polar bear stocks in the Beaufort Sea. Arctic 58:247-259. http://arctic.journalhosting.ucalgary.ca/arctic/index.php/arctic/article/view/426
Pdf here.

Atwood, T.C., Bromaghin, J.F., Patil, V.P., Durner, G.M., Douglas, D.C., and Simac, K.S., 2020. Analyses on subpopulation abundance and annual number of maternal dens for the U.S. Fish and Wildlife Service on polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska: U.S. Geological Survey Open-File Report 2020-1087. https://doi.org/10.3133/ofr20201087. pdf here.

Bromaghin, J.F., McDonald, T.L., Stirling, I., Derocher, A.E., Richardson, E.S., Rehehr, E.V., et al. 2015. Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline. Ecological Applications 25:634–651.

Conn, P.B., Chernook, V.I., Moreland, E.E., Trukhanova, I.S., Regehr, E.V., Vasiliev, A.N., Wilson, R.R., Belikov, S.E. and Boveng, P.L. 2021. Aerial survey estimates of polar bears and their tracks in the Chukchi Sea. PLoS ONE 16(5): e0251130. https://doi.org/10.1371/journal.pone.0251130 OPEN ACCESS video: https://doi.org/10.1371/journal.pone.0251130.s003

Crockford, S.J. 2018. State of the Polar Bear Report 2017. Global Warming Policy Foundation Report #29. London. pdf here.

Crockford, S.J. 2019. The Polar Bear Catastrophe That Never Happened. Global Warming Policy Foundation, London. Available in paperback and ebook formats. Crockford, S.J. 2020. State of the Polar Bear Report 2019. Global Warming Policy Foundation Report 39, London. pdf here.

Crockford, S.J. 2021. The State of the Polar Bear Report 2020. Global Warming Policy Foundation Report 48, London. pdf here.

Frey, K.E., Comiso, J.C., Cooper, L.W., Grebmeier, J.M. and Stock, L.V. 2021. Arctic Ocean primary productivity: the response of marine algae to climate warming and sea ice decline. 2021 NOAA Arctic Report Card, DOI: 10.25923/kxhb-dw16

Meier, W.N. et al. 2021. Sea ice. 2021 NOAA Arctic Report Card, DOI: 10.25923/y2wd-fn85

Regehr, E.V., Hostetter, N.J., Wilson, R.R., Rode, K.D., St. Martin, M., Converse, S.J. 2018. Integrated population modeling provides the first empirical estimates of vital rates and abundance for polar bears in the Chukchi Sea. Scientific Reports 8 (1) DOI: 10.1038/s41598-018-34824-7  https://www.nature.com/articles/s41598-018-34824-7

Rode, K.D., Regehr, E.V., Douglas, D., Durner, G., Derocher, A.E., Thiemann, G.W., and Budge, S. 2014. Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Global Change Biology 20(1):76-88. http://onlinelibrary.wiley.com/doi/10.1111/gcb.12339/abstract

Rode, K. D., R. R. Wilson, D. C. Douglas, V. Muhlenbruch, T.C. Atwood, E. V. Regehr, E.S. Richardson, N.W. Pilfold, A.E. Derocher, G.M Durner, I. Stirling, S.C. Amstrup, M. S. Martin, A.M. Pagano, and K. Simac. 2018. Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity. Global Change Biology http://onlinelibrary.wiley.com/doi/10.1111/gcb.13933/full

Rode, K.D., Wilson, R.R., Regehr, E.V., St. Martin, M., Douglas, D.C. & Olson, J. 2015. Increased land use by Chukchi Sea polar bears in relation to changing sea ice conditions. PLoS One 10 e0142213.

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January 2, 2022 at 02:46PM

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