It is late August, and I’m climbing down from a small peak in northern Washington as snow swirls around me. My fingers, toes, and limbs are all numb. Every now and then I can see Canada just on the other side of the ridgeline, before the mist closes in again. Not ideal, I think to myself. Not ideal.
My coworker and I pick our way down the rocky trail, back towards a small creek we had spotted earlier in the day. We’re here in the North Cascades looking for a creature that has often felt like the proverbial needle in a haystack – the enigmatic northern forestfly, Lednia borealis.
While the name is a bit of a misnomer – it is found primarily above the treeline – the northern forestfly is a species of stonefly that is classified as a Species of Greatest Conservation Need in the state of Washington. Working in partnership with the U.S. Forest Service and Washington Department of Fish and Wildlife, my colleagues and I have spent some time nearly every summer of the last seven years searching for this species and several other aquatic insects of conservation concern in alpine regions of the state. Our primary goal is to determine where these species occur, but we’re also interested in the overall community composition of the water bodies in which they’re found, and what habitat features might be important to their survival.
Stoneflies play an important role in alpine ecosystems
If you’re unfamiliar with stoneflies, these are insects that spend the majority of their lives underwater, where they feed on other invertebrates, submerged leaves, or benthic algae. Adults are terrestrial, active for a short period in which their main focus is reproduction. In high elevation environments, stoneflies serve as food for other species, including birds, and play integral roles in nutrient cycling, since species that eat algae and other plant matter convert the nutrients captured in primary production into a valuable food source. Like many freshwater invertebrates, they are threatened by habitat loss, pollution, and climate change. Cold-adapted alpine species like the northern forestfly are particularly threatened by extinction due to their patchy distributions, limited dispersal abilities, and reliance on cold water habitats.
Climate change threatens alpine ecosystems
Climate change is a growing threat to high elevation species, dramatically altering alpine ecosystems as glaciers recede and annual snowfall levels decline. For animals like the northern forestfly that live in snowmelt and glacier-fed streams, the rapid loss of meltwater sources has pretty clear and dire implications. In the Skagit River watershed alone – which is located in the North Cascades and is home to a number of northern forestfly populations and the most extensive glacial cover of any U.S. basin outside of Alaska – this decline has translated to a 25% reduction in meltwater in the last 50 years.
Surveys discover new populations of rare stonefly
What does this mean for species like the northern forestfly? The overall picture looks grim, but recent research and our own findings have given us some reasons to be hopeful. For one, the increased survey efforts that Xerces and our partners have undertaken over the last few years have resulted in a larger than previously known range and distribution of this species, which is heartening. Prior to the start of our survey efforts in 2015, Lednia borealis had been documented from just nine sites in northern Washington. We were curious if the species was found throughout the Cascades, but surveys throughout the southern and central parts of the range have proven largely unfruitful – despite surveying over 60 sites over a three year period, we did not detect a single individual.
Yet as we moved north, our success improved. We had our first positive detections in 2018 at two sites in the Glacier Peak Wilderness, and since then we have found Lednia borealis at multiple sites in the North Cascades, including several places that had not been surveyed since the 1980s. The species is now known to occur in at least 23 sites in Washington and is likely found in even more.
The extent of potential habitat for the northern forestfly has also grown. Because we have been incorporating genetic barcoding into our work, we’ve had some unexpected findings, including the revelation that the northern forestfly appears to occur in the mountains of British Columbia, Canada – approximately 600 km north of our Washington sites! Given the relatively extensive glacial habitat that still exists in that region of the world, it is very possible that these mountains could prove to be a stronghold for the species.
In the meantime, we will continue our efforts in Washington. The results from these surveys are already being used to help identify conservation priorities and management actions in Washington, and will be incorporated into the 2025 update of the State Wildlife Action Plan. Beyond contributing to ongoing regional efforts among partners, this work also provides much needed genetic data to barcoding libraries, forms a baseline for long term species and climate change monitoring, and expands our collective knowledge of the Lednia genus as a whole—and mountain stream biodiversity overall—in the West.
- Distribution of the northern forestfly, Lednia borealis Baumann and Kondratieff 2010 (Plecoptera), in Washington, USA. Fallon et al. 2022. Western North American Naturalist.
- Stoneflies in the genus Lednia (Plecoptera: Nemouridae): sentinels of climate change impacts on mountain stream biodiversity. Green et al 2022. Biodiversity and Conservation.
- WDFW species profile: Lednia borealis, Northern Forestfly
- Wings essay: On Being an Invertebrate Conservation Detective
- Xerces Society webinar series: Stories from the Field: Surveys for Alpine Streamflies in Washington’s North Cascades