The U.S. Fish and Wildlife Service has reopened the public comment period for its proposal to list two tiny, mountain stream-dwelling insects as threatened.

The western glacier and meltwater lednian stoneflies measure less than a centimeter in length, and stay close to the frigid streams high in the Montana and Wyoming backcountry. But their ecological importance stretches further.

“They need the coldest temperatures of any stonefly that we’re aware of,” Fish and Wildlife Service Biologist Jim Boyd told the Daily Inter Lake, “so they’re kind of a barometer for climate change.”

Rising stream temperatures and reduced stream volume, he continued, could spell trouble for the stoneflies, and the animals that rely on them.

“They support populations of predators ranging from other aquatic insects, to birds, to even some mammals, so certainly it’s a loss of a food source for some of those animals,” Boyd said. “Whether they can adapt…is yet to be seen.”

The Fish and Wildlife Service first proposed listing these insects as “threatened” under the Endangered Species Act in October 2016, taking public comments as required. Since then, new findings about the animals have prompted them to do so again.

The agency’s initial proposal cited the presence of 58 known meltwater lednian stonefly populations, all within Northwest Montana, and just four known populations of western glacier stonflies, “all within the boundaries of GNP (Glacier National Park).”

But knowledge of the animals is growing. In August 2016 – too late for the initial proposal – researchers documented one population in Southwest Montana’s Absaroka-Beartooth Wilderness, and three in Northwest Wyoming’s Grand Teton National Park. Another study published in March found more occupied streams and springs in those areas.

That bodes well for the species’ future survival, Boyd explained. “It helps the species hedge its bets against climate change if they’re a little spread out.”

But the stoneflies’ southern outposts may face trouble, too.

“The effects that we’re predicting for Glacier, we’re predicting similar things down there,” he said.

The expanded range proved significant enough to prompt the federal agency to reopen the comment period until Nov. 30.

“We’re going to reopen the comment period so we can accept additional comments about the range of the species,” agency Public Information Officer Steve Segin said.

Once it closes and the public’s input is incorporated, the “threatened” listing could be either withdrawn or finalized and published in the Federal Register.

The law spelling out this process, the Endangered Species Act, states that, “Whenever any species is listed as a threatened species...the Secretary [of the Interior] shall issue such regulations as he deems necessary and advisable to provide for the conservation of such species.” These include designating “any habitat of such species which is then considered to be critical habitat.”

“Critical habitat” desigations can draw intense opposition from people who use those areas. But Boyd pointed out that the parks and wilderness areas where these stoneflies have been found are already “fairly well-protected.”

In his view, that doesn’t mean the listing is a wasted exercise.

“If we were to still arrive at a threatened or endangered listing, there’s always that awareness component,” he argued, “to highlight the fact that these habitats are changing from the global phenomenon of climate change.”

The public can view the proposal at www.regulations.gov at Docket number No. FWS–R6–ES–2016–0086; 4500030113. The Regulation Identification Number is 1018–BB52. Comments will be accepted until Nov. 30. They may be submitted electronically on regulations.gov, or by mail to: Public Comments Processing, Attn: FWS–RX–ES–201X–XXXX; U.S. Fish & Wildlife Headquarters, MS: BPHC, 5275 Leesburg Pike, Falls Church, VA 22041-3803.

More information about these species is available on the agency’s websites at: https://www.fws.gov/mountain-prairie/es/meltwaterLednianStonefly.php and at https://www.fws.gov/mountain-prairie/es/westernGlacierStonefly.php.

Reporter Patrick Reilly may be reached at 758-4407 or preilly@dailyinterlake.com.