Supporting Science
Summary of Studies
Part 1: Predicted Vulnerabilities
Study Area
Beginning in 2020, we set out to determine which fishes in our headwaters study area (see map) are the most vulnerable to stream warming caused by climate change. To figure this out, we expanded a stream temperature model to include eastern Montana (NorWeST: EMonSTeR), built a fish-occurrence dataset with over 40,000 samples, and used 2 different methods to determine individual species upper thermal tolerances. We were able to do this for 28 different species or subspecies.
By applying future climate scenarios to sites where those 28 species have been found, we determined 14 to be vulnerable to stream warming. You can view interactive maps for each of these species on the home page.
The Postglacial Pioneer Hypothesis
One specific group of fishes we identified as having particularly vulnerable to climate change is postglacial pioneer species. Postglacial pioneer species are those fishes that first colonized northern latitudes after the last Ice Age and often require cool temperatures. A subset of these species with disjunct and often patchy distributions are known as glacial relicts. The video below explains this hypothesis in greater detail.
Part 2: Observed Trends
Evaluating Species Trends to Test Predictions
In a follow-up study, we evaluated trends of species across much of the same region (excluding the Columbia River basin) and looked at what factors may be driving these trends. Many of the species we predicted to be vulnerable to climate change were indeed declining, but not all. In particular, we found glacial relicts to be experiencing some of the largest declines. The broader group of postglacial pioneer species also appears to be declining, but some species are stable or even increasing. As such, we found support for the above postglacial pioneer hypothesis with caveats.
Warming temperatures were identified as the main predictor of species declines. Stream fragmentation was the second most important predictor. Taken together, it is clear that climate-vulnerable fishes need both cool and connected habitats.
Part 3: Single-Species Studies
Due to limitations with the data we were able to obtain, we were not able to evaluate the climate vulnerability of all native fishes in the region upon first attempt. So, we highlight findings of several additional studies that predict other species in the region to be vulnerable to climate change.
Finescale Dace Study in the Black Hills, WY-SD: Booher and Walters 2022
This study predicted the contemporary and future distribution of Finescale Dace in the Belle Fourche River basin in an attempt to identify potential translocation sites for this glacial-relict species. In so doing, they predict extreme losses for Finescale Dace due to expanding invasive species and stream warming.
Publications
Clancy, N. G., P. E. Budy, and A. W. Walters. In review. Ice Age biogeography corresponds with current climate vulnerability of freshwater fishes.
Clancy, N. G., and A. W. Walters. In prep. Multi-species climate refugia and the decline of glacial relict fishes across the Rocky Mountains - Great Plains continuum.