Western land managers could shrink the carbon footprint of wildfires by setting more prescribed burns, a new study says.
Igniting small, controlled fires reduces fuel buildup in the forest, helping to stave off the catastrophic fires that release millions of tons of carbon, according to research by the National Center for Atmospheric Research in Boulder, Colo.
When a mature ponderosa pine goes up in flames, it emits about 3 metric tons of stored carbon. Regular burning of underbrush helps protect those bigger trees, said Christine Wiedinmyer, the study’s co-author.
“With a prescribed burn, you’re leaving a lot of the larger trees standing,” she said. “So, you’re releasing less carbon to the atmosphere. Those larger trees also continue to suck up carbon dioxide. … It’s kind of a double bonus.”
The study is the first landscape-scale look at how prescribed burns affect carbon emissions. Widespread prescribed burning could reduce carbon output from forest fires by an average 18 percent to 25 percent, the researchers found. In some forest types, the carbon reductions were as high as 60 percent.
The scientists based their work on modeling and satellite images. They estimated that the United States could reduce its annual carbon output by 14 million metric tons through judicious use of controlled burns. That’s equal to about 0.25 percent of the nation’s yearly carbon output.
Wiedinmyer cautioned that the calculations are preliminary.
“It’s not the final answer on this question,” she said. “This pushes us to do more regionally specific studies.”
Prescribed burns hold most promise in drier forests, where fires return at more frequent intervals. The study focused on ponderosa pine, mixed conifer and dry Douglas fir forests.
Mechanical thinning of trees could yield some of the same benefits, though the study didn’t look at that, Wiedinmyer said.
Putting out fires became a core mission of the U.S. Forest Service after 1910, the year that wildfires charred more than 3 million acres in Idaho, Montana and Eastern Washington. As a result of the fire suppression, many Western forests are tinderboxes of dead wood.
In recent years, however, the Forest Service has been working to reintroduce fire to the ecosystem, said Steve Rawlings, fire management officer for the 1.1 million acre Colville National Forest.
Controlled burns are set on roughly 6,000 acres of the Colville forest each year. Most of the prescribed burning occurs between mid-May and mid-June, depending on weather. The Idaho Panhandle National Forests and Bureau of Land Management’s Coeur d’Alene District also burn about 5,000 acres annually.
“What we’re burning is below the amount that burned historically,” said Mark Grant, a Forest Service and BLM fire management officer in Coeur d’Alene. But getting the public to accept controlled burns takes time, he added.
“People still don’t like smoke in the air,” Grant said.