Mountain glaciers are disappearing around the world, including in iconic locations like Glacier National Park in northwestern Montana. With the recession of glaciers come dramatic changes in downstream habitats. As habitats are altered and meltwater sources dwindle, organisms adapted to the cold conditions of glacier-fed stream face increasingly uncertain futures. By linking high-resolution invertebrate data for 129 sites across the Glacier National Park alpine to fine-scale glacial records dating to Little Ice Age (~170 years ago), Scott et al. were able to ask a key question: what happens to mountain stream biodiversity as glaciers recede? They found that a distinct “cold-water” community lives in headwater streams and this cold-water community is persisting in places that have not been glaciated in 170 years! These findings challenge the notion that headwater stream invertebrates are cold stenotherms that are acutely sensitive to stream warming and opens the door to new questions about their physiological limits and how biotic drivers (e.g., competition) may shape their distributions.
Link to study: https://www.pnas.org/content/early/2020/05/12/2001697117