Publications

Incorporating Spatial Heterogeneity in Temperature into Climate Vulnerability Assessments for Coastal Pacific Streams.

Citation

Fullerton, A.H., Lawler, J.J., Lee, S.Y., and Torgersen, C.E.  (2017). Incorporating Spatial Heterogeneity in Temperature into Climate Vulnerability Assessments for Coastal Pacific Streams. Final Report to the North Pacific Landscape Conservation Cooperative.


Abstract

Water temperature, a key driver of ecological processes in aquatic environments, is expected to warm as a result of climate change, stressing stream biota. Successful climate adaptation strategies will consider changes to spatial patterns in water temperature. We analyzed water temperature for 6,106 km of rivers to evaluate the characteristics of cold-water habitat for Pacific salmon and steelhead within the NPLCC. We used a dataset of river surface temperature measured using airborne thermal infrared (TIR) remote sensing and multiple models to: (1) characterize thermal heterogeneity in rivers, (2) assess potential future thermal heterogeneity, and (3) illustrate salmon vulnerability in the Snoqualmie (Washington) and Siletz (Oregon) river watersheds. We found that cool-water habitat was prevalent at higher elevations and latitudes. Cool patch distribution and characteristics were specific to each river, but cool patches were generally larger and closer together upstream. Thermal heterogeneity was present at scales <1 km, which was only discoverable when using the nearly spatially-continuous TIR data, and likely could not have been predicted using models. As waters warm, the current distribution of cool patches will change, with downstream cool patches disappearing and warmer patches bisecting previously cool patches upstream. The vulnerability analysis suggested that thermal habitat conditions in August are already stressful and will remain so for salmon and steelhead in the Snoqualmie watershed. In the Siletz watershed, numerous cold patches previously accessible to salmon in the lower river reaches may disappear, making migration potentially more difficult in the future. Findings and datasets produced during this project will help resource managers in their quest to protect “sufficiently distributed” thermal refuges for Pacific salmon and steelhead, to identify locations where stream temperature patterns may be least/most responsive to climate change, and actions that will promote future thermal diversity best suited for conserving salmon and other aquatic resources.