Ringed seal biologist Steven Ferguson, in a statement to a reporter from the Winnipeg Free Press, made one of the boldest predictions I’ve ever heard:
“Hudson Bay could experience its first free winter within 5-10 years.”
You heard it here, folks. It appears Ferguson thinks Hudson Bay was never ice-free in winter even during the Eemian Interglacial, when the Bering Sea was ice-free in winter – something that has not come close happening in recent years (Polyak et al. 2010:1769).
Sounds like a bit of ill-advised grandstanding to me.
The Winnipeg Free Press reported Ferguson’s claim yesterday that ringed seal numbers in Hudson Bay declined by almost 80% the spring after the late freeze-up year of 2010, as part of a non-peer reviewed conference paper he gave (so no one can see the data he’s talking about).
However, polar bear surveys were done that summer and found no decline in numbers. The mark-recapture study (Lunn et al. 2016), you will recall, surveyed only about 1/2 of Western Hudson Bay territory so their estimate of about 800 bears was invalid for comparison to previous years. An aerial survey of the entire subpopulation the same year (Stapleton et al. 2014) found about 1030 bears – statistically, no change since the last estimate in 2004 (the IUCN PBSG uses 1030 as the official population size).
Southern Hudson Bay bears also showed no decline in numbers after 2010, as indicated by a survey undertaken in 2011 and 2012 (Obbard et al. 2015, 2016). The most recent Foxe Basin survey (Stapleton et al.2015) was done just before (summers of 2009 and 2010) the supposed decline of seals in the spring of 2011.
So, if Hudson Bay ringed seals suffered a “near-catastrophic” decline in numbers in the spring of 2011 after the late freeze-up in fall 2010, there must still have been plenty of seals left to feed the polar bears that depended on them for survival.
Apparently, ringed seal numbers rebounded after the spring decline of 2011 but Ferguson either failed to say to what levels or the reporter failed to mention it.
Well yes, I guess they did recover because how else could polar bears have come ashore this summer in such spectacularly good condition if seal numbers were still profoundly low?
For perspective, have a look at this previous post on Hudson Bay seals and the effect of variations in snow cover (for which Ferguson provided much of the data).
Quotes from the WFP article:
Ringed seal population in the Hudson Bay is declining.
A near-catastrophic plunge in the population of ringed seals in Hudson Bay is being blamed on melting sea ice caused by global warming, says a study led by a Manitoba researcher.
The population has been diminished by 75 per cent since aerial surveys started 20 years ago, according to data that will be presented to the ArcticNet conference of scientists in Winnipeg this week.
Lead researcher Steve Ferguson, a scientist with Fisheries and Oceans Canada and the University of Manitoba, said global warming is causing sea ice to disappear earlier in spring and form later in the fall, and there is less of it in Hudson Bay.
And in turn, the polar bear population will suffer because seals are the main component of their winter diet. The problem is compounded, as less sea ice means the bears have less area to hunt.
Hudson Bay could experience its first ice-free winter within five to 10 years, Ferguson said
“I don’t think polar bears and seals will be able to adapt. I think they’ll just die out in places like Hudson Bay. There’s little to stop the trend in loss of sea ice, even if we stop producing greenhouse gasses,” he said.
The study’s findings portend disaster for the Arctic generally.
“Hudson Bay is the early warning area of climate change because it is so far south,” Ferguson said. “We’re seeing the changes more dramatic in Hudson Bay, and it’s showing us how the rest of the Circumpolar Arctic will be impacted.”
Ferguson said while many people believe climate change is gradual, aerial surveys reveal mammals can disappear in huge numbers in a short period of time.
After a particularly warm 2010, the seal population plunged almost 80 per cent. Seal immune systems seemed to weaken, making them more susceptible to pathogens. Some of that loss has been recovered, he said.
Aerial surveys are not really “population surveys,” but are the most accurate available indicator, and they show a definite trend. They’re done each spring by counting seals on the ice.” [my bold]
Lunn, N.J., Servanty, S., Regehr, E.V., Converse, S.J., Richardson, E. and Stirling, I. 2016. Demography of an apex predator at the edge of its range – impacts of changing sea ice on polar bears in Hudson Bay. Ecological Applications, in press. DOI: 10.1890/15-1256
Obbard, M.E., Stapleton, S., Middel, K.R., Thibault, I., Brodeur, V. and Jutras, C. 2015. Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys. Polar Biology 38:1713-1725.
Obbard, M.E., Cattet, M.R.I., Howe, E.J., Middel, K.R., Newton, E.J., Kolenosky, G.B., Abraham, K.F. and Greenwood, C.J. 2016. Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice. Arctic Science, in press. 10.1139/AS-2015-0027
Polyak, L., Alley, R.B., Andrews, J.T., Brigham-Grette, J., Cronin, T.M., Darby, D.A., Dyke, A.S., Fitzpatrick, J.J., Funder, S., Holland, M., Jennings, A.E., Miller, G.H., O’Regan, M., Savelle, J., Serreze, M., St. John, K., White, J.W.C. and Wolff, E. 2010. History of sea ice in the Arctic. Quaternary Science Reviews 29:1757-1778. http://bprc.osu.edu/geo/publications/polyak_etal_seaice_QSR_10.pdf
Stapleton S., Atkinson, S., Hedman, D., and Garshelis, D. 2014. Revisiting Western Hudson Bay: using aerial surveys to update polar bear abundance in a sentinel population. Biological Conservation 170:38-47. http://www.sciencedirect.com/science/article/pii/S0006320713004618#
Stapleton, S., Peacock, E., and Garshelis, D. 2015. Aerial surveys suggest long-term stability in the seasonally ice-free Foxe Basin (Nunavut) polar bear population. Marine Mammal Science 32(1):181-201.