The resilience of polar bears in an ever-changing Arctic
Optimism in conservation science — which the Smithsonian says we desperately need (Earth Optimism Summit 21-23 April 2017, apparently a huge success) — means it’s time to acknowledge and celebrate real conservation success stories.
The Smithsonian folks probably won’t say it but I will — one of those successes is the recovery of polar bears.
It’s time to abandon the focus on prophesies of impending loss and accept that recovery of polar bears from the over-hunting of last century has continued despite a decade of low summer sea ice (Aars et al. 2017; Crockford 2017; Dyck et al. 2017; SWG 2016; York et al. 2016).
Why not focus on the numerous images of fat, healthy bears rather than the anomalous starving ones?
It’s time to let go of imagined future catastrophes based on pessimistic failures of adaptation (Amstrup et al. 2007, 2008; Atwood et al. 2016; Stirling and Derocher 2012) and acknowledge that polar bears and Arctic seals, just like Pacific walrus (MacCracken et al. 2017; US Fish & Wildlife Service 2017), are resilient species with adaptive capabilities we are are only just beginning to comprehend (Crawford and Quakenbush 2013; Crawford et al. 2015; Escajeda et al. 2018; Rode et al. 2014; Stirling and Lunn 1997; Stirling et al. 1975a; Vibe 1965).
US Fish and Wildlife Service Press Release (4 October 2017), my bold:
“The U.S. Fish and Wildlife Service has found that the Pacific walrus does not require protection as threatened or endangered under the Endangered Species Act (ESA). The finding follows a comprehensive review and analysis of the best available scientific information concerning the species, as well as local and traditional ecological knowledge of Alaska Native peoples.
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While walruses use sea ice for a variety of activities, including breeding, birthing, resting and avoiding predators, they have shown an ability to adapt to sea ice loss that was not foreseen when the Service last assessed the species in 2011.
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“Our decision not to list the Pacific walrus under the Endangered Species Act at this time is based on a rigorous evaluation of the best available science, which indicates the population appears stable, and the species has demonstrated an ability to adapt to changing conditions,” said Fish and Wildlife Service Principal Deputy Director Greg Sheehan. “If future circumstances warrant or new information comes to light, we can and will re-evaluate the Pacific walrus for ESA protection. In the meantime, the species will continue to be federally protected under the Marine Mammal Protection Act.”
Polar bears, like Pacific walrus, will be protected in the US under the Marine Mammal Protection Act even if ESA protection is canceled.
Giving up ESA protection would not throw conservation values and protection to the wind: it would just take away an unnecessary complexity that is not well supported by science (Crockford 2017; Crockford and Geist 2017).
After all, the Marine Mammal Protection Act provided the support that allowed polar bear numbers to rebound after decades of over-hunting in the US.
It’s time to accept that the survival of these species through thousands of years of massive changes in sea ice habitat— the like of which modern field biologists have never seen — is sound evidence of their innate adaptive ability (Cronin et al. 2014; Cronin and Cronin 2015).
Cronin and Cronin (2015) state (my bold):
“Despite the scale, frequency and rapidity of Quaternary climate changes, Arctic marine ecosystems associated with sea-ice habitats were extremely resilient, adapting through geographic range expansion into the Arctic during warm periods, and south into extra-Arctic regions during glacial periods. The stratigraphic record of the last 1.5 Ma indicates that no marine species’ extinction events occurred despite major climate oscillations.”
Sea ice may change in the future, as it has done in the past, but polar bears and their prey will almost certainly continue to exist.
In 2014, geneticist Matthew Cronin had this to say about a recent polar bear genetic study announced in a University of Alaska Fairbanks press release (pdf here) :
“The ramifications are that if the polar bear was an independent species for about 1 million years it survived previous cold and warm periods,” Cronin said. “This means the polar bear has been an independent lineage a long time through glacial and interglacial and warm periods.”
The last glacial period was at maximum extent about 22,000 years ago and was preceded by a warm interglacial period about 130,000 years ago. Other warm and cold periods preceded that. Cronin thinks that if polar bears survived previous warm periods in which there was little or no arctic summer sea ice, this should be used in models predicting the species’ response to current climate change.
“It seems logical that if polar bears survived previous warm, ice-free periods, they could survive another. This is of course speculation, but so is predicting they will not survive, as the proponents of the endangered species act listing of polar bears have done.” [my bold]
Instead of hand-wringing, perhaps we should celebrate the fact that Arctic nations came together in 1973 to protect polar bears from a scourge that evolution could not have anticipated — the relentless slaughter by humans with guns (Honderich 1991; Stirling 2011), and how those individual nations followed with their own protective legislation.
We have polar bears in abundance today because people in the 1960s and early 1970s saw that a different future was possible and did something about it.
It’s time to thank those dedicated people for their service (Ian Stirling included) and put the issue of polar bear survival to rest: polar bears have been saved.
Optimism and curiosity should drive the conservation agenda forward (e.g. Swaisgood and Sheppard 2010), not the relentless pessimism that turns good news into a personal attack (e.g. Harvey et al. 2017).
Maybe it’s time to turn to pure scientific research to help us understand how polar bears adapt so well to change.
Maybe it would be better if we removed the need to justify Arctic science with conservation and management objectives, including counting bears (an endeavor fraught with potential inaccuracies and wide margins of erroranyway), and accept that polar bears can take care of themselves as long as hunting regulations are in place and enforced.
Let’s do some real science that tells us interesting things we didn’t know before, such as how so many female polar bears in Western Hudson Bay in the 1980s were able to produce triplet litters and wean their cubs at one and half years old when no other subpopulation under study at the time was able to do so (e.g. Ramsay and Stirling 1988; Stirling and Lunn 1997)?
Or why — exactly — sea ice in the Eastern Beaufort Sea gets too thick in early spring to support ringed seals, bearded seals, and polar bears (Bromaghin et al. 2015; Burns et al. 1975; Harwood et al. 2012; Ramseier et al. 1975; Smith 1987; Stirling 2002; Stirling and Lunn 1997; Stirling et al. 1975a, 1975b, 1980, 1981, 1982, 1985)?
Polar bears have been saved but we can still use some solid polar bear science.
Read rest at Polar Bear Science
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