Quantifying the resilience of coldwater lake habitat to climate and land use change to prioritize watershed conservation

Abstract

Managing ecological systems for resilience can increase their capacity to maintain key functions even under global change. Oxygenated coldwater (oxythermal) habitat in lakes is an important ecological resource that is threatened by both climate change and eutrophication. Here, we quantify the resilience of oxythermal habitat in over 10,000 glacial lakes in the upper Midwestern United States to climate change and watershed disturbance and classify lakes for conservation prioritization based on their current conditions and resilience. Oxythermal habitat was predicted by lake morphometry, July air temperatures, and watershed land use. Temperatures are projected to increase by mid‐century, 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 containing suitable coldwater habitat was predicted to decline by 67%, while the number of lakes with unsuitable habitat was predicted to increase by over 200%. Lakes varied in the amount of temperature increase that they could sustain without a resultant change in habitat tier (i.e., their climate resilience). Median climate resilience was 4.3°C, with some lakes capable of remaining in their habitat tier even with temperature increases up to 14°C. Changing watershed land use was predicted to influence oxythermal habitat in 24% of lakes (n = 2391). We used the magnitude of increase in watershed development that a lake could sustain while remaining in its current habitat class as a measure of its resilience to watershed disturbance. Conversely, decreased watershed development may improve oxythermal habitat conditions and push a lake into an improved condition, and this value represented a lake's restoration potential. We classified lakes into seven management classes based on their current oxythermal habitat conditions and the resilience of oxythermal habitat to climate and watershed disturbance. 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 lakes and how it is influenced by local action across a multistate region, we can prioritize conservation action across multiple scales to maintain the critical habitat and ecosystem function of glacial lakes.

A continuous classification of the 476,697 lakes of the conterminous US based on geographic archetypes

“…Implications for predicting lake response to broad scale change Globally, lakes are subject to stressors such as climate and land use change that have complex interactions and diverse response trajectories (Hayes et al 2015;Zia et al 2016;Hansen et al 2022). The design of monitoring programs to collect in situ ecosystem data is notoriously challenging because of the need to capture the full range of ecologically relevant heterogeneity that exists at both local and regional scales (Janousek et al 2019;Soranno et al 2020).…”

Investigations of Lake Trout Salvelinus namaycush Ecology and Behaviour in Relation to Fragmented Thermal Habitats to Inform a Multifaceted Management Strategy

“…Shifts in season duration (e.g., extended springs) have already been shown to change Lake Trout phenologies, causing reduced spatial occupancy of spring littoral habitats, influencing prey consumption, and growth . Cold-water habitats are particularly susceptible to anthropogenic stressors that are vital for cold-water fishes (e.g., Lake Trout; Tunney et al 2014;Hansen et al 2022) and my thesis provides direct evidence on how important thermal habitats are in the context of bioenergetics for this cold-water fish.…”

“…Furthermore, regulations could be developed to limit habitat modification and development (e.g., shoreline modification) that will reduce thermal habitat complexity, thus protecting cold-water habitats that are important for Lake Trout (Jacobson et al 2016;Tingley et al 2019;Hansen et al 2022). Continued research focused on how Lake Trout use complex multibasin lakes will provide scientists and decision-makers with better information and tools to sustainably manage Lake Trout populations…”

“…Populations of freshwater fishes worldwide are declining due to anthropogenic activities and stressors (Butchart et al 2010;Reid et al 2019). Fishes that are reliant on cold-water habitat face increased stressors because these habitats are rapidly changing (Kraemer et al 2021;Hansen et al 2022). My thesis contributes to the existing literature on the biology and ecology of a coldwater fish, Lake Trout, by providing scientists and managers with new knowledge and perspectives on how Lake Trout function in an ecosystem with complex and isolated thermal habitats.…”

“…As the capacity for movement and access to optimal habitats become limited, fish might face additional constraints if resources (e.g., prey and shelter) are limited in suboptimal habitats (Martinson et al 2012), thereby potentially affecting population size and condition (Hayes et al 1996;Link et al 2020). Understanding the influences of thermal habitat fragmentation, specifically fragmentation of sensitive and important cold-water habitats, on the spatial ecology of fish is important because freshwater ecosystems continue to be negatively influenced by anthropogenic stressors (Reid et al 2019;Hansen et al 2022). Lake Trout (Salvelinus namaycush) are cold-water fish, that rely heavily on cold oxythermal habitats to grow, reproduce, and survive (Gibson and Fry 1954;Martin 1966;Magnuson et al 1979).…”