Many people don't think much about winter ice on the Great Lakes unless they live on their shores. But a new international review led by Dr. Marguerite Xenopoulos, the Canada Research Chair in Global Change of Freshwater Ecosystems at Trent University, is characterizing what the loss of winter ice means for everything from drinking water to shoreline protection to industries worth billions of dollars annually across the region. 

The study is the first comprehensive synthesis of the social, cultural, economic, and ecological consequences of declining ice cover across the Great Lakes watershed. With research contributed by Trent graduate students, the review concludes that ice cover is a critical part of the natural infrastructure that supports not just environmental systems, but the livelihoods of about 40 million people. 

"Lake ice is like a master switch. When it disappears, an extraordinary number of interconnected ecological and societal processes change at the same time," said Prof. Xenopoulos, who is also a professor of Biology at Trent. "While many people think of winter as an inconvenience, this review shows we rely quite a lot on consistent cold conditions." 

The erosion of ecosystem services  
The review found that the impacts of declining winter ice extend across nearly every major category of ecosystem service, the benefits nature provides to people. Shrinking ice cover affects clean drinking water, healthy fisheries, shoreline integrity, recreation, and Indigenous cultural practices. 

Cold-water fish species such as lake whitefish, walleye, and yellow perch depend on winter conditions for spawning success and juvenile survival. Those species support commercial, recreational, and Indigenous fisheries worth more than $5 billion annually across the region. 

Ice also acts as a natural shield for coastlines. Historically, shore-fast ice helped absorb wave energy and reduce winter erosion. As that protective barrier disappears, coastal communities face increased shoreline loss, damage to infrastructure, and rising adaptation costs. 

Winter conditions play an important role in maintaining water quality as well. Ice cover suppresses algal growth and allows nutrients and sediments to settle.  

Yet warmer winters are increasingly common. The Super El Niño is forecasted to bring a historic warm winter season, which closely follows history-setting winters in both 2023 and 2024 for lowest ice cover on the Great Lakes. Warmer winters can increase nutrient runoff while reducing those natural processes, creating conditions that favour harmful algal blooms that threaten drinking water supplies and summer recreation.  

The consequences are cultural as well as ecological. For many First Nations communities around the Great Lakes, ice supports ceremony, harvesting, travel, teaching, and the transfer of knowledge between generations. As ice becomes less reliable, these practices become more difficult to sustain. 

Winter recreation and tourism are also feeling the effects. Ice fishing, skiing, snowmobiling, and winter festivals generate billions of dollars in economic activity, but shorter and less predictable winters are already reducing opportunities for businesses and communities that depend on them. 

The researchers also note that some impacts of warmer winters are not all negative. Longer ice-free periods can extend the shipping season, reduce transportation costs, and lengthen summer tourism opportunities. However, when considered across the full range of services winter provides, the losses outweigh the gains. 

What Can People Do? 
While addressing climate change requires broad action, the researchers say individuals can help protect Great Lakes ecosystems and adapt to changing winters. 

They encourage residents to be safe around lake ice, treating it as increasingly unpredictable, especially during mild winters; reduce road salt use by shovelling early and applying only what is needed; avoid spreading fertilizer or manure before winter thaws; and support investments in Great Lakes research, monitoring, and restoration programs. 

The study also emphasizes that continued cooperation between Canada and the United States will be essential.  

"The Great Lakes have long been a model for binational environmental management," said Prof. Xenopoulos. "Understanding and responding to winter change will require the same collaborative spirit." 

The researchers identify four priorities to support the health of the Great Lakes. Expanding winter monitoring across the basin, better tracking climate and health impacts, understanding how communities adapt when winter services disappear, and engaging Indigenous communities, industry, anglers, and local residents as partners in future research are all important for ultimately preserving the services provided by this freshwater system for people. 

"I've spent more than a decade changing the perspective among scientists and government officials about the importance of winter on freshwater ecosystems," said Prof. Xenopoulos. "This study makes it clear how important ice cover is not only to lake ecology, but to humans' way of life, both for those who spend time on the ice and water and those who don't." 

This study was first published in the American Geophysical Union journal Earth’s Future.