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Too much climate uncertainty to declare wolverines endangered, says U.S. agency

Wolverines are not threatened by climate change and don’t need protection under the Endangered Species Act (ESA), the U.S. Fish and Wildlife Service (USFWS) announced yesterday. After more than a year of analysis, the agency is citing scientific uncertainty in withdrawing its controversial proposal to list the snow-dwelling carnivores as threatened. But some conservation scientists are concerned that the agency’s reversal sets a precedent that will restrict using models of future climate in listing decisions.

Wolverine listing isn’t about whether USFWS believes that climate is changing, said the agency’s director, Dan Ashe, during a teleconference with reporters. The question is how well scientists can predict fine-scale warming impacts on the snow caves wolverines use to rear their young. “We know too little about the ecology of wolverines, and the climate models that we have available to us today don’t provide the specificity of information about the potential effect of climate changes on the specific type of habitat that wolverines seem to prefer to use for denning,” he said. “So we can’t make a reasonable prediction that wolverines will be likely endangered in the foreseeable future.”

USFWS did not have those concerns in February 2013 when it first proposed protecting wolverines (Gulo gulo luscus) as threatened under the ESA. Populations of the predator were hit hard by trapping and poisoning in the early 20th century but have rebounded somewhat in recent decades. Researchers estimate approximately 300 “mountain devils” now live in the continental United States, found mostly in Montana, Idaho, and Wyoming. But modeling studies suggest that the persistent spring snowpack wolverines use for denning will decline 31% by 2045 and 63% by 2085.

However, two wolverine biologists from USFWS’s seven-person peer-review panel strongly critiqued a listing based on those models. They were particularly concerned that biologists haven’t described the mechanism explaining why wolverine dens are associated with deep spring snowpack. In April 2014, a new panel reviewed the science, leading USFWS staff overseeing the process to recommend listing wolverines.

But last month, a leaked memo from a USFWS regional director reversed that recommendation, calling the conclusions based on available models “speculative.” The Society for Conservation Biology, the American Society of Mammalogists, and 56 ecologists and biologists wrote letters asking USFWS to reconsider the reversal.

Yesterday’s announcement dashed those hopes—and raised concerns that the agency will have difficulty listing any species as a result of concerns about future climate change. “I think the [agency] is asking for such a burden of proof tying climate change to species persistence that it would be practically impractical to meet for most species,” said Carlos Carroll, a conservation biologist with the Klamath Center for Conservation Research in Orleans, California, and the president of the Society for Conservation Biology’s North America section. “Effectively it’s a way of sort of ignoring climate change as a threat because you can say, well, it’s uncertain.”

Ashe responded to that concern by saying the agency is open to reconsidering listing if presented with more evidence of climate impacts on wolverines, such as the correlations they saw between declining polar bear populations, lower polar bear body fat, and declining sea ice. “We definitely see the climatic effects, temperature and precipitation change—particularly of snowfall—across the range of the wolverine,” he said. “But what we’re missing is that more detailed, refined information. “

The wolverine would have been the first animal in the lower 48 states to receive federal protection primarily due to climate threats, joining polar bears and ringed and bearded seals in Alaska. The three states with the largest wolverine populations had opposed the listing, in part because they are wary of additional federal oversight on the public lands where most wolverines live.

Conservation groups say they are planning to go to court in a bid to reverse today’s decision. “In dealing with uncertainty in ESA listing decisions there is no law that says you have to give the species the benefit of the doubt,” said Melanie Rowland, a retired National Oceanic and Atmospheric Administration attorney and ESA expert who was not involved in the listing decision. “But certainly the agency has every right to say that the scientists are not certain, but they are confident enough that we think that the drafters of the ESA would want the species to be protected.”