Great Lakes water levels reached record highs this summer, covering new ground and encroaching on property owners from Wisconsin to New York.
And while water levels historically follow high-low cycles, sustained high levels threaten coastal wetlands and the wildlife and people who rely on their benefits.
The Great Lakes are a series of freshwater seas, with more than 11,000 miles of shoreline surrounding drinking water used by 34 million people. For thousands of years, coastal wetlands have served as the transition area between deep waters offshore and the grasslands and forests inland. Those coastal wetlands serve numerous roles for life in the Great Lakes basin, including wildlife habitat, flood prevention, and water quality control.
Prior to human development, the location of these coastal wetlands shifted with lake levels, providing a constantly moving buffer. But as water rose this summer and overtook many marshes, the new levels often met roads, houses and farms.
Michigan's Manistee Marsh is on the coast of Lake Michigan.
Existing coastal wetlands will remain healthy if waters follow historical patterns and recede. But if climate change sets a new normal for Great Lakes levels, human development may prevent new coastal wetlands from taking shape in many areas.
“Everything would change if the landscape changes,” said Kali Rush, Ducks Unlimited biologist in Michigan.
Higher lake levels with no room for coastal wetlands have several compounding impacts, Rush said. Coastal wetlands are nature’s sponges, soaking up water and slowly releasing it.
“Having more of these wetlands helps subdue flood surge,” she said. “Fewer wetlands mean more intense flooding and erosion of the shoreline.”
The hundreds of species of plants and animals that live in coastal wetlands would be homeless. Dabbling ducks that need shallow water would lose cover and their food source. Shorebirds that rely on mud flats would be forced to move on to new territories.
And while Great Lakes water volume would increase, the quality of that water would face greater pressure. Wetlands filter runoff from human development, including vehicle pollutants and algae bloom-causing fertilizers. Take away those filters and contaminants would have a direct path to the Great Lakes.
Additional invasive species could fill the void left behind without wetlands. Invasive plants need less hospitable conditions to take root, especially in areas not conducive for traditional wetland complexes.
The U.S. Army Corps of Engineers announced in early September that based on preliminary August data, Lake Superior tied its record high for the month while Lake St. Clair and Lake Erie established new record high monthly mean water levels in August. Water levels on Lake Michigan-Huron and Lake Ontario were slightly below record highs, but still very high compared to average.
“We don’t know how long lake levels will take to rebound because we simply don’t know what the future climate will be,” Rush said. “But what’s important is protecting the pristine coastal areas we already have to not make the situation worse.”
About 60 percent of historic wetlands have been lost in the Great Lakes area to human development, and continued loss is estimated at one percent annually.
Ducks Unlimited combats these losses through its Great Lakes Initiative, and the results are impressive. Since 2012, more than 40,000 acres of wetlands and associated uplands have been protected, restored or enhanced. Learn more about the Great Lakes Initiative.