Nav: Home

Burn without concern

June 21, 2017

The USDA Forest Service in the Boundary Waters Canoe Wilderness Area (BWCWA) will continue to use controlled burns without worrying about fish health in associated watersheds, researchers say.

"Fire is a part of this community," said soil scientist Randall Kolka of the USDA Forest Service Northern Research Station, one of the lead authors in the study. "By using it you can lessen the chance of wildfire."

Controlled burns prevent wildfires from ripping through the BWCWA in northern Minnesota. The million-acre area encompasses forested hills, wetlands, over 1,100 lakes, and hundreds of miles of streams. Without occasional burns, fallen trees accumulate like matchsticks, creating the perfect environment for uncontrollable wildfires.

That's what happened on July 4, 1999 in the BWCWA. Strong winds felled millions of trees on swath from North Dakota all the way to Maine. After this blowdown event, the Forest Service began prescribed burns to prevent future wildfires.

But the Forest Service was concerned about the consequences of prescribed burns on the health of pristine lakes and streams in the area. In addition to the environmental concerns, there are economic ones: the wilderness area attracts over 250,000 visitors a year.

"This is a Class 1 Wilderness," said Kolka. "We have people coming in from all over: scouts, fishing enthusiasts, hikers, canoeists, and kayakers."

Specifically, Kolka wanted to know if the burns add mercury, toxic at very low levels, to fish in the watershed.

Mercury's path to the wilderness is complex. Fossil fuels burnt elsewhere release mercury into the atmosphere. This airborne mercury can travel great distances until it finally falls, lodging in soil or vegetation. The Forest Service worried forest fires were releasing this fallen mercury and carrying it into water bodies where it could contaminate fish.

Previous research on wildfires and mercury levels show mixed results. Some studies indicate higher levels of mercury in fish after severe fires. Other studies show that prescribed burns can disrupt the food web of watersheds by adding nutrients that leads to higher mercury. Still other research shows little effect of prescribed or wildfires on fish mercury levels.

Regardless, Kolka said the health risks of mercury made it imperative for the Forest Service to understand how their burns were affecting mercury levels in local fish.

"We wanted to follow the mercury from the atmosphere, through the soils, and into the food chain," said Kolka.

So Kolka and group of researchers from the USDA Forest Service, the University of Minnesota, and Stockton University compared two similar lakes in the BWCWA over nine years. The two lakes are shallow, small, and surrounded by forests and wetlands. During the experiment, two fires (a low-severity prescribed fire in 2004, and a moderate severity wildfire in 2007) disturbed one watershed. The other watershed remained untouched by fire.

The researchers checked mercury concentrations in yellow perch before and after the two fires. They also examined soils and lake chemistry to see how the fire affected the watershed generally. Then they compared the fire-affected lake to the untouched lake.

The researchers found that although wildfires release the mercury in the soil, it didn't necessarily end up in the fish. The fires had no effect on mercury levels in yellow perch. The fires also didn't seem to significantly disrupt watershed food webs.

"We found no direct effect," said Kolka. "So we can't point the finger at forest fires." Kolka said the mercury from the forest fires was likely deposited somewhere else downwind from the fires.

However, none of the fires were severe. One of the fires was the Forest Service's controlled burns. The other began naturally and was more intense, but moderate compared to severe wildfires. Kolka said the next step is to measure the impact of a severe wildfire. The Forest Service will continue to monitor the area, and pay close attention when a major wildfire occurs.
-end-
Read more about Kolka's research in Journal of Environmental Quality. This research was funded by the Joint Fire Sciences Program and the USDA Forest Service Northern Research Station.

American Society of Agronomy

Related Mercury Articles:

New nanomaterial to replace mercury
Ultraviolet light is used to kill bacteria and viruses, but UV lamps contain toxic mercury.
Wildfire ash could trap mercury
In the summers of 2017 and 2018, heat waves and drought conditions spawned hundreds of wildfires in the western US and in November, two more devastating wildfires broke out in California, scorching thousands of acres of forest, destroying homes and even claiming lives.
Removing toxic mercury from contaminated water
Water which has been contaminated with mercury and other toxic heavy metals is a major cause of environmental damage and health problems worldwide.
Fish can detox too -- but not so well, when it comes to mercury
By examining the tissues at a subcellular level, the researchers discovered yelloweye rockfish were able to immobilize several potentially toxic elements within their liver tissues (cadmium, lead, and arsenic) thus preventing them from interacting with sensitive parts of the cell.
Chemists disproved the universal nature of the mercury test
The mercury test of catalysts that has been used and considered universal for 100 years, turned out to be ambiguous.
Mercury rising: Are the fish we eat toxic?
Canadian researchers say industrial sea fishing may be exposing people in coastal and island nations to excessively high levels of mercury.
New estimates of Mercury's thin, dense crust
Michael Sori, a planetary scientist at the University of Arizona, used careful mathematical calculations to determine the density of Mercury's crust, which is thinner than anyone thought.
Understanding Mercury's magnetic tail
Theoretical physicists used simulations to explain the unusual readings collected in 2009 by the Mercury Surface, Space Environment, Geochemistry, and Ranging mission.
Mercury is altering gene expression
Mercury causes severe neurological disorders in people who have consumed highly contaminated fish.
Climate changes may lead to more poisonous mercury in plankton
Global warming is expected to increase runoff and input of organic matter to aquatic ecosystems in large regions of the Northern hemisphere including the Baltic Sea.
More Mercury News and Mercury Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Accessing Better Health
Essential health care is a right, not a privilege ... or is it? This hour, TED speakers explore how we can give everyone access to a healthier way of life, despite who you are or where you live. Guests include physician Raj Panjabi, former NYC health commissioner Mary Bassett, researcher Michael Hendryx, and neuroscientist Rachel Wurzman.
Now Playing: Science for the People

#544 Prosperity Without Growth
The societies we live in are organised around growth, objects, and driving forward a constantly expanding economy as benchmarks of success and prosperity. But this growing consumption at all costs is at odds with our understanding of what our planet can support. How do we lower the environmental impact of economic activity? How do we redefine success and prosperity separate from GDP, which politicians and governments have focused on for decades? We speak with ecological economist Tim Jackson, Professor of Sustainable Development at the University of Surrey, Director of the Centre for the Understanding of Sustainable Propserity, and author of...
Now Playing: Radiolab

An Announcement from Radiolab