Sea Grant Experts Contribute to Statewide Climate Report

Six members of the Sea Grant staff contributed to the 2021 Wisconsin Initiative on Climate Change Impacts report. Contributing writer Dea Larsen Converse, WICCI communications director, shared updates based on two portions of the report — fisheries and coastal processes.

A focus on climate impacts to Wisconsin’s Great Lakes in the most recent assessment from the Wisconsin Initiative on Climate Change Impacts (WICCI) wicci. wisc.edu shows Great Lakes water level fluctuations and changes to water temperature, lake mixing and ice cover are affecting Great Lakes water quality and habitats. The last two decades have been the warmest on record in Wisconsin and the past decade has been the wettest.

“Climate change is stressing all ecosystems. Protecting coastal habitats and thinking about future conditions when planning habitat restorations can build climate resiliency into our ecosystems,” said Titus Seilheimer, WICCI Great Lakes Working Group co-chair and Sea Grant fisheries specialist.

The Great Lakes basin is home to more than 3,500 species of fish and wildlife and provides drinking water, recreation and livelihood to more than 34 million people. Rapid changes in Great Lakes water levels, extreme storms and longer wet periods are affecting the coastal wetlands, beaches and dunes that provide habitat in the basin and protect water quality and shorelines. In addition, more frequent extreme precipitation events and warming waters are increasing the risk of microbial contamination on beaches and toxic blue-green algal blooms in lakes. For example, in 2018, extreme storm events elevated nutrient levels along the South Shore of Lake Superior for months and fueled major algal blooms along the shoreline. While Green Bay has been experiencing algal blooms for decades, it is a concerning new phenomenon in Lake Superior. Extreme storms also bring contaminants that have the potential to move through the food web into fish that are important for subsistence fishers.

Changes in air temperature also influence the amount of ice cover, water levels, clarity and chemistry associated with fish habitat. For example, the decreasing extent and duration of Great Lakes ice cover increases erosion and impacts fall and winter fish spawning beds. Warming Great Lakes water temperatures mean cold-water fish will likely move north into deeper parts of the lakes and more thermal habitat for cool-water fish like walleye will open up in Lake Superior. However, changing precipitation patterns could potentially lower their growth rates and damage spawning habitat.

Further specifics can be examined with regard to coastal communities. These large fluctuations in Great Lakes water levels along with flooding and bluff erosion from extreme storms are affecting lakes Michigan and Superior coastlines and causing uncertainty for coastal communities.

“Coastal communities and businesses will need to adapt to more volatile lake level fluctuations, with frequent fluctuations between extreme high and low lake levels, as the climate continues to warm,” said Adam Bechle, WICCI coastal resilience co-chair and Sea Grant coastal engineer.

All of Wisconsin’s Lake Michigan and Lake Superior coasts experienced extreme lake level fluctuations in the past decade. Along Lake Michigan, record high water levels in 2020 followed record low water levels in 2013. At low water levels, coastal-dependent industries are at risk for insufficient water depths for navigation. At high water levels, concerns include increased erosion, flooding, bluff failure and infrastructure damage. Both high and low water level extremes are anticipated under a changing climate along the Great Lakes coastline. This could include potentially higher highs, lower lows and more rapid fluctuations than seen in the historical record. The high variability in water levels combined with bigger waves and storm surge from extreme storms will continue to increase erosion and decrease the stability of coastal bluffs.

Wave energy reaching Great Lakes coasts is expected to increase in the future, in part due to anticipated decreases in ice cover extent and duration. Nine of the top 10 lowest ice cover years have occurred since 2002. Projections show that ice cover duration on Lake Superior will decrease by one to two months by the end of the century as the climate continues to warm. Greater wave energy reaching the coast will lead to increased erosion and flooding of the shoreline. During times of higher water levels, these large waves will be able to reach further inland and cause greater coastline erosion and flooding. In some coastal communities, the areas with the highest risk of coastal flooding are also home to low-income and other vulnerable populations.

The Wisconsin Initiative on Climate Change Impacts (WICCI) is a statewide collaboration of scientists and stakeholders formed as a partnership between UW– Madison’s Nelson Institute for Environmental Studies and the Wisconsin Department of Natural Resources. WICCI’s goals are to evaluate climate change impacts on Wisconsin and foster solutions.—DLC