The simple fact is that if polar bear experts had been right about the threat to polar bears from the loss of summer sea ice in the Arctic, there would be no polar bears in Churchill this fall. No bears for tourists to photograph, none for biologists to study, and certainly none for the BBC to film for an upcoming three-part TV special called “Arctic Live.”
The low-ice future that biologists said would doom polar bears to extinction by 2050 has already happened in 8 out of the last 10 years. The sea ice future has been realized.
Polar bears have experienced those supposedly deadly low-ice summers for almost a decade but the global population did not drop by 2/3 as predicted and not a single one of the ten subpopulations predicted to be extirpated under those conditions has been wiped out.
How much more wrong can you be than that? Will the BBC mention this conundrum in their show? Will the polar bear experts they consult share this fact with viewers? We’ll all have to watch and see [show times and summaries of each program here, 1-3 November] but here are some background facts that might enhance your viewing experience.
UPDATE: Sea ice condition of Hudson Bay at 1 November 2016 below from the Canadian Ice Service (some slushy ice looks to be forming along the coast north of Churchill – this is how freeze-up starts). See the animation for the last 10 days here:
We’ve already had the sea ice future
“Dominant outcomes of the BN model were for extinction [extirpation] of polar bear populations in the Seasonal Ice and Polar Basin Divergent Ecoregions by 45 years from present [2050]… Our modeling suggests that realization of the sea ice future which is currently projected, would mean loss of ≈ 2/3 of the world’s current polar bear population by mid-century.” (Amstrup et al. 2007:1-2) [my bold]
Assuming low summer sea ice like we’ve had for 8 out of the last 10 years, total eradication of Western Hudson Bay polar bears – as well as extirpation of bears in nine other subpopulations – is what USGS polar bear researchers predicted when they filed their reports in 2007 to support listing polar bears as ‘threatened’ under the US Endangered Species Act (Amstrup et al. 2007; Durner et al. 2007). Eradication of those ten subpopulations (plus declines in others), the experts said, would cause the global population to decline by 67%.
In 2007, USGS experts predicted that all of the bears in the green and purple regions would be wiped out if sea ice declined to low extents by 2050. However, the ice declined faster than expected – we’ve had that dreaded sea ice future since 2007, and polar bears thrived. Not a single one of those 10 subpopulations has disappeared.
In other words, predicted devastation of polar bear populations did not require summer sea ice to disappear completely – just to drop to levels like we’ve seen since 2007.
Yet, almost a decade of polar-bear-destroying sea ice levels did virtually none of the damage predicted to occur – fat polar bears still come ashore in Western Hudson Bay and migrate through Churchill waiting for ice to form, and not a single subpopulation (let alone ten) has been wiped out (Wiig et al. 2015).
Global polar bear numbers have not declined at all, let alone a decline of 67% – in fact, the latest estimate of 22,000-31,000 polar bears worldwide (IUCN Red List, 2015) is the highest it’s ever been.
Check out the images (below) of predicted September ice extents (> 50% concentration) predicted for 2051 and 2098 (Durner et al. 2007; Durner et al. 2009), which will of course be smaller in area than the ice maps supplied by NSIDC that track ice >15% concentration:
This situation is not news to the polar bear experts that predicted a gloomy future for the bears back in 2007.
The figure below is from Amstrup et al. 2008 (a peer-reviewed version of the USGS report (Amstrup et al. 2007) used to support the ESA listing of ‘threatened’). It states that “…five of the models we used in our analyses project more perennial sea ice [i.e. what’s left at the Sept. minimum] at mid-century than was observed in 2007.”
I’ve added the 2007 15% concentration level at the Sept. minimum to compare to the 50% concentration level they provide (note that 2016 reached the same low as 2007 [UPDATE but more like 2008 according to NASA]:
More on this issue here.
Churchill bears in fine shape this year
As I pointed out more than three months ago, the word from bear guides north of Churchill in late July 2016 was this:
“Bear numbers are up spectacularly this year and all are looking very fat and healthy, perhaps much to the chagrin of climate change “experts.”
And the first report from the Churchill Polar Bear Alert program (week of July 11-17, 2016) had this to say:
“Bears are off the sea ice and on land. They are looking well fed and in great shape.”
Links to pertinent posts
Here are links to some pertinent posts that might answer questions you have after watching the show (all are based on peer-reviewed literature and cite the references quoted, usually with links to where you can find the papers themselves. If you see one you’d like to read but cannot find it, send me a message via the “Contact Me” page and I will see that you get it).
1) Western Hudson Bay polar bear numbers are stable, no trend in ice breakup or freeze-up
This needs saying again: the latest study on Western Hudson Bay polar bears reveal the population has been stable since 2004 and there has been no significant trend in either breakup or freeze-up dates since 2001.
2) Recent studies show Sept ice of 3 to 5 mkm2 did not kill polar bears off as predicted
Recall that in 2006, the IUCN Polar Bear Specialist Group based their conservation status of ‘vulnerable’ (likely to become threatened within the next 45 years due to reduced habitat) on the predictions of sea ice specialists (see 2008 update here).
Sea ice experts in 2005 predicted such low summer sea ice extents as polar bears have endured since 2007 (3.0 – 5.0 mkm2) would not happen until 2040-2070, at which time PBSG biologists said that >30% of the world’s bears would be gone.
3) IUCN Red List says global polar bear population is 22,000 – 31,000 (26,000 mean)
If global numbers do decline over the next 35 years, it will be from a high point not previously acknowledged by the IUCN Polar Bear Specialist Group (PBSG).
4) Condition of S Hudson Bay polar bears varies with freeze-up only says new study
Despite the fact that the polar bears of Southern Hudson Bay (SHB) live further south year round than any others, a recent study found their average body weight has declined relatively little since the 1980s. There has been no decline in the size of the population over that time either.
References
Amstrup, S.C., Marcot, B.G. and Douglas, D.C. 2007. Forecasting the rangewide status of polar bears at selected times in the 21st century. Administrative Report, US Geological Survey. Reston, Virginia.
Amstrup, S.C., Marcot, B.G., Douglas, D.C. 2008. A Bayesian network modeling approach to forecasting the 21st century worldwide status of polar bears. Pgs. 213-268 in Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications, E.T. DeWeaver, C.M. Bitz, and L.B. Tremblay (eds.). Geophysical Monograph 180. American Geophysical Union, Washington, D.C. http://onlinelibrary.wiley.com/doi/10.1029/180GM14/summary and http://alaska.usgs.gov/science/biology/polar_bears/pubs.html
Durner, G.M., Douglas, D.C., Nielson, R.M., Amstrup, S.C., McDonald, T.L. and 12 others. 2007. Predicting 21st-century polar bear habitat distribution from global climate models. Administrative Report, US Geological Survey. Reston, Virginia.
Durner, G.M., Douglas, D.C., Nielson, R.M., Amstrup, S.C., McDonald, T.L. and 12 others. 2009. Predicting 21st-century polar bear habitat distribution from global climate models. Ecological Monographs 79: 25–58.
Wiig, Ø., Amstrup, S., Atwood, T., Laidre, K., Lunn, N., Obbard, M., Regehr, E. & Thiemann, G. 2015. Ursus maritimus. The IUCN Red List of Threatened Species 2015: e.T22823A14871490. http://www.iucnredlist.org/details/22823/0
You must be logged in to post a comment.