A couple of weeks ago, new Montana federal judge Dana L. Christensen ordered the U.S. Fish and Wildlife Service (USFWS) to reconsider wolverines for protective status under the Endangered Species Act (ESA), as a “snow-dependent species standing squarely in the path of global climate change,” declaring USFWS’s decision “against listing the wolverine as threatened […] arbitrary and capricious” driven by “immense political pressure.”
That was a big surprise, especially since USFWS brags how wolverines have “made a steady recovery in the past half-century after hunting, trapping and poisoning nearly extirpated the species from the lower 48 states.”
Further, it’s not just the Feds saying this for political reasons; the International Union for the Conservation of Nature (IUCN) maintains a “Red List of Threatened Species,” monitoring the “conservation status” of plant and animal species for which there is “adequate data.” Species not extinct are ranked in five classes from “Critically Endangered” down to “Least Concern.”
Guess what? IUCN ranks wolverines as Least Concern, meaning “widespread and abundant.” Even more interesting, the global status of wolverines has improved steadily from Vulnerable in 1988 to least concern today.
Allowances are made, of course, for local issues. But again, guess what? The Red List cites research showing that, in big, wild, high, cold British Columbia, wolverine home ranges are about 200 square kilometers (km2). In melting Montana, which of course is genetically connected to BC wolverines, home range is 65 km2 – specifically, world “densities range from one per 500 km² in Scandinavia to one per 65 km² in Montana, USA.”
Now, how could the thickest population of wolverines on the entire Planet Gaia, which weirdly enough is peripheral habitat, be at risk? What in tarnation is Judge Christensen thinking?
Spring snow.
IUCN (and just about everyone else) has established that wolverines give birth in snow dens, requiring a “persistent” snowbank five feet deep that lasts until the kits, born between February and April after delayed implantation and gestation, are ready. Building on this understanding, in 2011, a team of government scientists modeled “persistent” snow cover (deeper than 13 centimeters) as “a proxy for the biological needs of the wolverine.” Their model explored if present habitats would remain effective for winter denning in the wake of fossil-fuel-driven anthropogenic climate change. They “found” up to a 67 percent decline in large areas of May snow by 2099. Scary, right? Well, not so fast …
The authors presumed wolverines could only “originate” from contiguous snow areas of 225 km2, dropping smaller areas from the habitat ranks as their model warmed up. They didn’t consider whether or not a home range could still present working den sites over part of a specific home range – as the authors wrote, “we do not know how fine-scale changes in snow patterns within wolverine home ranges may affect population persistence.” In other words, they can’t say if Momma Wolverine will or won’t just raise her kits in the next snowdrift over if her old favorite melts.
Further, the authors assumed that traveling on snow has only 1/20th the “movement cost” of traveling “outside snow-covered areas.” Again, “movement cost” was determined on a genetic exchange (mating – which happens in summer) basis that probably hinges mainly on gross terrain characteristics (mountain versus flatlands) rather than direct energy expenditure over specific surfaces (snow or dirt) during the denning period.
Remember the news stories about that super-wolverine that zoomed straight up and over a mountain, stunning and impressing researchers? The bottom line: Wolverines cover ground, snowy or not, hunting for what they need. And they are really good at finding what they need – including, I’m sure, that comfy snowbank.
So, while this study is “best available science,” which the USFWS and courts are required to incorporate in policy, “best” sometimes isn’t even “good.” Only one of a handful of very preliminary studies about wolverine denning, the study is very coarse scale, giving no real insight into how wolverines might actually respond to snow-cover changes.
For Judge Christensen to grant such inconclusive science the full power of law is a huge disappointment, and a huge danger.