The U.S. Fish and Wildlife Service made the controversial proposal last year to lift the endangered and threatened species designation across the entire country for grey wolves.
Less than two decades after biologists took dozens of wolves from Alberta to revive the species, which had been hunted to near-extinction, the suggestion sparked heated debate. After a public comment period was repeatedly extended due to the overwhelming response, the agency asked for an independent review.
That opinion was a unanimous no.
"The service's proposed rule is not easily characterized as reasonable," Steven Courtney, chairman of the panel, wrote in the report released Monday by the National Center for Ecological Analysis and Synthesis at the University of California Santa Barbara.
Beginning in 1995, dozens of wolves were taken from Jasper National Park in Alberta and moved to Yellowstone National Park in the U.S. The animals had been hunted to extinction by 1926 in the park, which straddles Wyoming, Idaho and Montana.
The experiment worked, and the animals thrived, but their recovery was not welcomed by all.
Under pressure from ranchers and state officials, the U.S. Fish and Wildlife Service relinquished wolf management to Idaho and Montana almost a decade ago. Other states followed, and the political struggle continued until the agency proposed lifting protection last year in all contiguous U.S. states.
But the panel said there is not enough science available to justify lifting the protection.
The agency recommendation is based, in part, on a controversial theory that the grey wolf never existed on the East Coast or Great Lakes regions of the country, but rather those areas were home to a distinct eastern wolf species.
"It is widely agreed by both sides that despite this evidence, the theory that the eastern wolf is a distinct species is controversial and therefore, in the absence of dramatic new evidence, the conclusion now that the eastern wolf is well supported as a distinct species ... is surprising," Dr. Robert Wayne, a geneticist from UCLA, wrote in the report.
"I am just stating for the record that there is still a controversy out there," Wayne said at a December meeting where the recommendation was under discussion.
The U.S. Fish and Wildlife Service said the relocated wolves in Yellowstone exceeded recovery goals for 11 consecutive years, so they were delisted and management turned over to the states.
"The proposed rule is based on the best science available and incorporates new information about the wolf's current and historical distribution in the contiguous United States and Mexico," the agency said on its website.
But the panel found that was not the case. The agency's recommendation lacked critical analysis, the experts said, and the necessary scientific evidence is not there.
Dr. W.W. Murdoch said the agency relied on a study by four of its own employees, published in its own publication.
"This seems a less than optimal way of establishing the best scientific statement on a controversial issue," Murdoch wrote, adding it would be best to base such decision on scientific study published in a peer-reviewed journal.