Feeling the burn: Wildfires increasingly threaten US lakes

According to a team of scientists led by Ian McCullough, a postdoctoral researcher in the Department of Fisheries and Wildlife at Michigan State University, U.S. lakes are facing a growing threat: wildfires.

July 15, 2019

Damage from the 2012 Reading Fire in Lassen Volcanic National Park, CA, photographed in 2016. Wildfires can have many effects on lakes, including increasing concentrations of nutrients and contaminants. Photos: Ian McCullough
Damage from the 2012 Reading Fire in Lassen Volcanic National Park, California, photographed in 2016. Wildfires can have many effects on lakes, including increasing concentrations of nutrients and contaminants. Photo by Ian McCullough.

According to a team of scientists led by Ian McCullough, a postdoctoral researcher in the Department of Fisheries and Wildlife at Michigan State University, U.S. lakes are facing a growing threat: wildfires. 

“Lakes are like funnels for the landscape”, said co-author Jean-François Lapierre, an assistant professor at the University of Montreal. “In this study, we ask how lakes feel the effects of surrounding fires in terms of nutrients, contaminants and water clarity.” 

Past research suggests that these effects may last years. For example, smoke and ash, as well as runoff from burned areas, can increase nutrients in lakes, making them more productive and likely to experience algae blooms. 

“This analysis is fairly unique," said co-author Max Moritz, a University of California Cooperative Extension Wildfire Specialist at UC Santa Barbara's Bren School. "There is relatively little known about how fire has and will be impacting lakes, so the work provided here will hopefully be useful to many studying these issues. 

McCullough also commented on how little lake fire research has been conducted in the past. 

“Most is from a handful of remote lakes in Canada,” he said. “In the U.S., we have many lakes that supply drinking water to large human populations, so we really need more research in this type of setting.” 

For example, the 2013 Rim Fire in the Sierra Nevada, California, made national headlines for burning to within meters of the Hetch Hetchy Reservoir, a critical source of drinking water for millions of people in the San Francisco metropolitan area. 

“Hetch Hetchy was a close call, but also a sign of what could happen in the future”, McCullough said. 

Wildfires are often associated with the western U.S., but this is not the only region where lakes experience wildfires. In fact, the state with the most lake watershed wildfires since 1984 is Florida, which also has the third most lakes among all states (behind Minnesota and Texas). 

Across the entire U.S., 6106 lake watersheds have experienced at least one wildfire since 1984, predominantly in the western U.S., Southern Great Plains and Florida. 

Although this represents only 4.4% of lakes in the lower 48 states, lake watershed wildfires have been increasing steadily through time, particularly since the mid-2000s. This is consistent with increasing frequency of large wildfires across the US over the same time. 

In Michigan, 1.8% of lake watersheds experienced wildfire since 1984. Although this number may seem low given the thousands of Michigan lakes, warming temperatures and longer, drier summers lengthen the “fire season”, or times of year when wildfire risk is high. This means that many regions of the U.S., including those not typically accustomed to wildfires, could experience more fire in the future. 

This summer, McCullough and his colleagues are beginning a follow-up lake fire study by compiling data from various lake monitoring agencies across the US. Comparing lakes across different regions will give lake managers a clearer idea of how different lakes may respond to fires and how long their recoveries might take. 

“It will be really interesting to compare, for example, how lakes in different places like Florida, California and Michigan respond to wildfires”, McCullough said. “At this point, we still don’t know. But hopefully we will soon.”

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