The photo of a lone polar bear on a tiny fragment of floating ice has become a powerful symbol of the impacts of global warming in the Arctic. This iconic animal has become climate change’s canary in the coal mine, but climate denier blogs love to claim the animals’ numbers are booming, largely based on the claims of one Canadian zoologist blogger.

A a new analysis in the journal BioScience examines 45 blogs that deny or question climate science, as well as 45 science-based blogs. Nearly all of the denier blogs say that, contrary to the opinions of many scientists who study them, polar bears are doing fine. In fact, 80 percent of these blogs reference a single site, a blog by zoologist Susan Crockford, who has not published any peer-reviewed papers on polar bears. It shows how climate denier messages spread online.

“These bloggers hope to use polar bears to cast doubt on global warming itself,” said co-author Steven Amstrup, chief scientist for Polar Bears International, a conservation-focused organization. This is a deliberate tactic to sow confusion in the minds of the public about the climate change science, just as the tobacco industry did about the link between smoking and cancer, Amstrup said in an interview with Motherboard.

“Social media makes it easy to amplify misinformation. And many readers believe and trust false claims without questioning or verification,” he said.

Amstrup has spent 30 years studying polar bears in Alaska, where the population fell 40 percent between 2000 and 2010 mostly due to loss of sea ice. In 2008 they were listed as a threatened species under the US Endangered Species Act, and in Canada they’re listed as a species of special concern. Polar bear populations in colder parts of the Arctic are holding up, but it’s clear that global warming and the loss of sea ice is an existential threat, Amstrup said.

Among denier blogs, authors found that the most popular source for material was a blog called Polar Bear Science by Crockford, a zooarchaeologist. (This refers to the study of animal remains from archaeological sites.)

Crockford operates a consulting company called Pacific Identifications that analyzes bone and shell fragments. She also holds an unpaid, adjunct position at the University of Victoria. Crockford acknowledges that she has never done any field research on polar bears. Nor has she spent any time in the Arctic, according to a 2016 report in Up Here magazine.

She told Motherboard that her lack of peer-reviewed research on polar bears is irrelevant. “I am a professional zoologist and quite capable of educating myself on any related topic,” Crockford said in an email.

Crockford is the go-to source on polar bears not just for climate denier blogs. She is also frequently cited as an polar bear expert and interviewed in conservative and mainstream media, including NBC. In late 2016, Crockford self-published two books, one for children and one that she called a “rational science reference book about polar bears readers around the world have been requesting.”

Why does Crockford devote so much of her time and energy writing and speaking about polar bears? “The blog was a new and different way to share what I’ve learned about polar bears and the Arctic with interested people around the world,” she said in an email.

Crockford also comments about polar bears at the Heartland Institute, a free-market think tank based in Chicago, with a long and ongoing history of attacking climate science and climate scientists. In 2012, internal Heartland documents revealed that Crockford received $750 per month from the Institute.

“You don’t have to read far in her material to see that it is full of unsubstantiated statements and personal attacks on scientists, using names like eco-terrorists, fraudsters, green terrorists and scammers,” Amstrup said. In a follow-up email on Friday, Amstrup clarified that these statements to Motherboard were meant to reflect the climate denier community as a whole, rather than Crockford in particular. In an email to Motherboard, Crockford denied using those terms on her blog.

This is about sowing doubt about climate change, hurting scientists’ ability to inform the public and delaying action on climate, Amstrup said.

Crockford called the BioScience paper a personal attack and a “peculiar brand of ‘scientific’ smearing” on her blog.

“Although the gullible media still pretends to believe the doomsday stories offered by these researchers, the polar bear has fallen as a useful icon for those trying to sell a looming global warming catastrophe to the public,” she wrote.

The BioScience study also analyzed the arguments made by 45 science-based blogs about the impacts of global warming on polar bear populations. Nearly all said that global warming threatens polar bear populations.

Update: This piece has been updated with new comment from Steven Amstrup. It has also been updated with new comment from Susan Crockford.