Land & Environment

Blowing Smoke: New Metric Quantifies Wildfire Smoke Threat to Lakes

By Daniel Carolan |

Lakes and rivers in North America are subject to various types of pollution, from toxic metal runoff to microplastics. But in the age of human-caused climate change, a certain type of contaminant is now raising concern among scientists who study natural bodies of water: wildfire smoke. A team of researchers, including Janice Brahney from the Department of Watershed Sciences and Ecology Center, has developed a new metric, the “lake-smoke day,” to help study these effects.

The lake-smoke day quantifies the number of days during the year that a lake is exposed to wildfire smoke.

“Something like this is especially relevant to the public, who’ve seen massive smoke events like last summer’s Canadian fires where smoke covered the East Coast and reached as far away as Europe,” said Brahney. “This impacted areas that are thousands of times larger than the fires themselves.”

According to the study, nearly 99% of lakes in North America had at least 10 lake-smoke days a year from 2019-2021, and almost 90% experienced at least 30.

“That was surprising, even to us,” said the lead author on the research, Mary Jade Farruggia of UC Davis. “With this study, we quantified for the first time the scope of the smoke problem. We show that it’s not just a widespread problem, but one that is long-lasting in a lot of places.”

The scientists used a mapping tool developed by the National Oceanic and Atmospheric Association that blends satellite imagery and on-the-ground measurements to evaluate smoke density. Combining that with a database of over 1 million North American lakes, they were able to determine exposure to wildfire smoke for individual bodies of water. Each of the researchers used their membership in the Global Lake Ecological Observatory Network to collaborate with other scientists to evaluate and communicate their findings.

With the frequency and severity of wildfires increasing worldwide, many studies have focused on the direct effects of wildfire within the watersheds where they take place. But given smoke’s ability to impact things well outside of a burn area like availability of sunlight, heat distribution, and the nutrient cycle by way of ash deposition, lakes may be particularly vulnerable, according to the study.

And while there are some likely known effects of smoke and ash deposition on lake ecosystems, very little research has been done to quantify those effects. There remains much to be learned when it comes to the degree and scope of their impacts, according to the researchers.

“We look to use this metric as a baseline to help measure smoke effects on water ecosystems,” Brahney said. “The lake-smoke day is one piece of the puzzle. There is already much known about wildfire impacts within burn areas, but very little is known about the broader impacts beyond the watershed, and this gives us a starting point to help quantify this issue on a global scale.”


Daniel Carolan
Staff Assistant
Quinney College of Natural Resources


Janice Brahney
Associate Professor
Department of Watershed Sciences


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