November 20, 2020
Quantifying resilience of coldwater fish habitat to climate change and watershed disturbance
Dr. Gretchen Hansen
Assistant Professor, UMN Department of Fisheries, Wildlife and Conservation Biology
Description
Coldwater fish habitat in lakes is threatened by both climate change and eutrophication. In some cases, management actions at local or regional levels can influence lake responses to climate change and maintain ecosystem services under the safe operating space framework. Here, we quantify the resilience of oxythermal habitat in lakes to climate change and watershed disturbance for over 10,000 glacial lakes in the upper Midwestern United States, and classify lakes based on their resilience and restoration potential. Coldwater fish habitat depends on lake morphometry, summer air temperatures, and watershed land use. Temperatures were projected to increase by mid-century throughout the region, and the magnitude of warming, its effect on oxythermal habitat, and the uncertainty surrounding that effect varied among lakes. Under mid-century climate conditions, the number of lakes supporting optimal or marginal coldwater habitat was predicted to decline while the number of unsuitable lakes was predicted to more than double. Managing watershed disturbance was predicted to influence the oxythermal habitat status in 41% of lakes (N=4263). The magnitude of increase in watershed disturbance that a lake could sustain while remaining in its current habitat class quantifies its resilience to watershed disturbance. Conversely, decreased watershed development may improve oxythermal habitat conditions and push a lake into an improved condition, and this represents their restoration potential. We classified lakes into 7 management classes based on their current oxythermal habitat conditions and their resilience to climate and landuse change. To facilitate management on individual lakes, we also assessed the vulnerability and resilience of individual lakes and the uncertainty surrounding these estimates. By quantifying the resilience of cisco lakes and how it is influenced by local action across a multi-state region, we can prioritize conservation action to maintain coldwater fish habitat.
Dr. Gretchen Hansen is an assistant professor in the Fisheries, Wildlife, and Conservation Biology Department at the University of Minnesota. Her research focuses on largescale drivers of change in freshwater ecosystems, including climate, land use, and invasive species. She is especially interested in how local management and lake characteristics influence the resilience of fish populations and communities to regional and global change. Gretchen previously worked as a research scientist for state fisheries management agencies, and is committing to conducting actionable science via collaboration with stakeholders and managers. To answer complex questions she employs multiple approaches including statistical analyses of historical data, observational field studies, simulation modeling, and large-scale experimentation.