Which of the following statements do you think is true?

A) Polar bear populations have been in decline for some time; or B) Polar bear populations are healthy.

The answer is not as straight forward as it may appear on the surface. 

For some time now the suggestion has been that polar bears are in trouble and that many sub-populations of Ursus maritimus are decreasing, making them an iconic symbol in the fight against global climate change. 

But there remains an ongoing debate within the scientific community that studies polar bears and their populations about whether the narrative of declining numbers is a stark reality or convenient myth. 

‘They could be gone in a couple of years’

Andrew Derocher, a professor of biological sciences at the University of Alberta, has spent his decades-long career studying polar bears, and has been more outspoken than most about the peril the big bear may face in the coming years. 

“Our estimation is that we probably won’t have polar bears in Churchill once we get out to mid-century ... They could be gone in a couple of years."

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The reported decline has made polar bears the poster species in the battle against climate change. However there is debate within the scientific community about the decline of the polar bears. (Susanne Miller/Reuters)

"Our estimations are, if we had a very early melt, and a very late freeze, we could see up to 50 per cent mortality in a single year. You put a couple of years like that back-to-back, and things could happen very quickly,” says Derocher, in reference to a worst-case scenario about certain sub-populations he has studied. 

The Polar Bear Specialist Group, a group that Derocher once chaired, estimates that globally there are up to 25,000 bears in the whole Arctic, with about two-thirds of those in Canada. It identifies at least four Canadian sub-populations in decline.

The UN's Intergovernmental Panel on Climate Change (IPCC) — often cited as the global authority on assessing long-term changes in Arctic sea ice levels — projects dramatic losses by the end of this century. Derocher says that without adequate ice flows to facilitate the bears' seal hunting, losses among sub-populations will likely be exacerbated.

Polar bears are not in trouble at the moment

But not everyone agrees polar bears are in trouble. Biologist Mitchell Taylor has studied polar bears and advised governments for more than thirty years, living in the high Arctic for much of that time.

“They’ve certainly been around through the last interglacial period,” says Taylor. “During that interglacial it was warmer than it is now: we had pine trees on Baffin Island, deciduous forests north of the Arctic Circle. Polar bears had to have survived that or we wouldn’t be seeing polar bears now,” he says.

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The UN's Intergovernmental Panel on Climate Change is projecting dramatic losses in the polar bear population by the end of the century, however some scientists disagree. (Michael Dalder/Reuters)

Taylor asserts that polar bear populations "don't appear to be declining" in any group that he is "aware of so far," and that the science of estimating polar bear numbers has never been precise. He says that many of the current estimates are based upon a lacking methodology, admitting that some of his previous work incorporated the allegedly faulty technique as well.

Taylor says the problem lies in the way population estimates are extrapolated from samples. 

“When you don’t sample the whole area you underestimate survival, you underestimate population numbers, and in fact the culmination of those biases can result in a scientific estimate that suggests a decline when none exists.”  

It was just over a decade ago, says Taylor, that the notion that polar bears could be threatened by climate change gained traction. But he takes issue with the IPCC's projection models for sea ice changes in the Arctic. 

In 2008, he signed the controversial Manhattan Declaration on climate change, which argued that there was no conclusive evidence that carbon dioxide emissions from modern industrial activity was causing catastrophic changes in global climate. 

“There was only one perspective, and that was what was provided by the IPCC,” says Taylor.

Taylor says that because he lived in the north he had direct contact with the people in the area, giving him a unique perspective on what was really happening on the ground. 

“What they were describing was quite simply inconsistent with what I was hearing from local people, what I was seeing myself.”

Ostracized by scientific community

When Taylor made his thoughts known, he says he expected a free exchange of ideas or at least a healthy scientific debate. Instead he says he was ostracized inside the polar bear scientific community.

“I’ve known those guys for like 20 years. They know me, they know I would never say or do anything to harm polar bears deliberately,” he says.   

Indeed, Taylor is not alone in his assertion that polar bear numbers are at a healthy level. Just last year Environment Canada reported that "The polar bear does not have a small wild population, it does not have a restricted area of distribution and no marked decline has been observed."

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Some scientists says the bears are not in trouble at the moment, and that they don’t appear to be declining in numbers. (Alexander Demianchuk/Reuters)

At the University of Minnesota in Minneapolis, Seth Stapleton is a new voice in polar bear research. He’s been developing methodology using satellite tracking to count polar bearsIn 2011 he conducted the largest aerial survey ever attempted in western Hudson Bay to estimate polar bear numbers.

Stapleton estimated a total population in the area of 1,030 bears — a figure very similar to a 2004 mark-recapture estimate.

How many polar bears are we talking about?

The Polar Bear Specialist Group's estimate of 25,000 polar bears currently left on the planet is in fact the highest figure proposed since researchers began attempting to count their numbers.

The international consortium of scientists has recently backed away from that number, however. 

Dag Vongraven, chairman of the PBSG, writes in an email that a footnote will be added to information on polar bear populations provided by the group. 

“As part of past status reports, the PBSG has traditionally estimated a range for the total number of polar bears in the circumpolar Arctic," the statement says.

"Since 2005, this range has been 20-25,000. It is important to realize that this range never has been an estimate of total abundance in a scientific sense, but simply a qualified guess given to satisfy public demand.”

Derocher says he is confident in the science, especially when it comes to climate change.

”There’s no debate,” says Derocher. “Scientifically, there’s no debate.”  

The models that project the loss of sea ice, he says, spell disaster for the polar bear.

Taylor is just as adamant. 

“In the end nature will speak and it will be clear who knew what they were talking about and who didn’t.”