Predicting Effects of Climate Change on Aquatic Ecosystems in the Crown of the Continent Ecosystem

Within the Transboundary Flathead River Watershed and Crown of the Continent Ecosystem (CCE), Canada and USA, this research is applying new and existing techniques for combining downscaled climate spatial data with fine-scale aquatic species vulnerability assessments (aquatic invertebrates and fish), population genetic data, and remotely sensed riparian and aquatic habitat analyses. Results may be used to identify populations and habitats most susceptible to the impacts of climate change; develop monitoring and evaluation programs; inform future research needs; and develop conservation delivery options in response to climate change, invasive species, and land-use stressors in the CCE. The work described below was accomplished with support from the Great Northern LCC and the Crown Managers Partnership.

The Transboundary Flathead River Watershed extends from British Columbia into Montana. Photo credit: Garth Lenz

Aquatic Invertebrates are Early Warning Indicators

MaxEnt model output of L. tumana distribution probabilty in Glacier National Park, MT, using current climate conditions (left panel) and future climate conditions (right panel), which show a decrease of 81%.
Lednia tumana nymph. Photo by Joe Giersch, USGS

One species that may be particularly vulnerable to climate-change-induced glacier loss is the meltwater stonefly (Lednia tumana), a species endemic to glacial and snowmelt-driven alpine streams in Waterton-Glacier International Peace Park and candidate for listing under the Endangered Species Act. We found that L. tumana inhabits a narrow distribution, restricted to short sections (~500 m) of cold, alpine streams directly below glaciers, permanent snowfields, and springs. Simulation models suggest that climate change threatens the future distribution of these sensitive habitats and the persistence of L. tumana through the loss of glaciers and snowfields. Mountaintop aquatic invertebrates are ideal early warning indicators of climate warming in mountain ecosystems and the CCE.

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Stream Temperature Models Assess Risk

Left map - Locations of temperature data loggers in the upper Flathead River system and Glacier National Park. Right map - Simulated exceedence of thresholds for critical bull trout habitats by the year 2059.

We are developing fine-scale submodels using high resolution (22 meter cells) data in a spatially-explicit framework to examine risk associated with increasing temperatures, modified hydrologic regimes, and disturbance events for aquatic species. We have established a stream temperature monitoring network (>300 sites) throughout the CCE. Spatially-explicit stream temperature models have been developed to predict water temperatures in streams throughout Glacier National Park and the upper Flathead River system. Models are being used to assess thermal exceedences for aquatic species under climate change scenarios.

More information:

  • LA Jones et al. In review. Use of Fine-scale Stream Temperature Modeling to Assess Potential Impacts of Climate Warming on Salmonid Habitats.

Simulator Assesses Genetic Diversity and Demography of Populations

An example riverscape with 19 subpopulations and 50 individuals per subpopulation. Left inset shows a spawning bed with 50 individual locations, right inset shows the riverscape with varying degrees of resistance values assigned to each pixel value in the stream network. The "Lake Source" is Flathead Lake, MT, to which species that have a migratory life history (e.g., Salvelinus confluentus) will migrate.

We developed a spatially-explicit landscape genetics simulator for aquatic species in complex riverscapes that tracks movements of individuals as functions of water temperature, flow, habitat complexity, physical barriers, and other variables. This novel approach allows researchers and managers to assess the impacts of stressors (e.g., climate change, invasive species, habitat loss) on the genetic diversity and demography of populations through time. This product and others will help produce vulnerability maps to guide restoration strategies for protection of the most threatened stream segments and populations at risk in the CCE.

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Nuisance Native Alga May Be Useful Indicator

Didymo abundance is positively related to modeled maximum summer stream temperatures in Glacier National Park.
Didymosphenia geminata colonized by blackfly larvae. Photo by Joe Giersch, USGS

Didymosphenia geminata (didymo) is a freshwater alga native to North America that has recently spread to lower latitudes and warmer waters, and increasingly forms large blooms that cover streambeds. We used a comprehensive monitoring data set from the National Park Service and US Geological Survey models of stream temperatures to explore the drivers of didymo abundance in Glacier National Park. Didymo abundance was positively related to summer stream temperatures, which are likely to continue increasing over the coming decades, thereby increasing the extent and severity of didymo blooms. Didymo may be a useful indicator of thermal and hydrological modification with climate warming across the Rocky Mountain region.

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Close-up view of the Flathead River in British Columbia. Photo credit: Michael Ready

This article was contributed by Clint Muhlfeld and Joe Giersch, Northern Rocky Mountain Science Center - US Geological Survey.

Products from this project will be available on the GNLCC's Landscape Conservation Management and Analysis Portal.