UM researchers: Let small wildfires burn to diminish large fires
Laura Lundquist
(Missoula Current) As increasing drought pushes western Montana toward a risky fire season, new University of Montana research indicates that wildfire suppression can worsen the effects of wildfire.
The scientific journal “Nature Communications” this week published a UM research project that used computer simulations to show that fire suppression increases the likelihood that subsequent wildfires will be worse than if the area had been allowed to burn under the right conditions.
“Fire suppression has unintended consequences,” said Mark Kreider, a Ph.D. student in the UM Forest and Conservation Sciences program. “We’ve known for a long time that suppressing fires leads to fuel accumulation. Here, we show a separate counter-intuitive outcome.”
Over the past 20 years or so, wildfires appear to have gotten bigger and more intense, particularly in the American West but also worldwide. Fuel accumulations due to long-term wildfire suppression in the U.S. can account for part of the reason, as can climate change, which worsens drought and heat. But the UM study takes the problem one step further to find that fire suppression, especially full-on wildfire attack, worsens conditions by leaving areas unburned that otherwise could have been cleansed by fire.
Researchers didn't have the option of using actual data. They would have needed to compare wildfires that were suppressed with those that weren’t. But there are too many other variables that would need to be controlled to create similar conditions - terrain, weather, wildfire intensity - and the authors say there are no landscapes, even wilderness, where fire is not somewhat suppressed.
So they turned to computer simulations, where they could select for specific situations. They could create a wildfire scenario, dialing particular conditions up or down with all other variables held constant to see if anything changed.
To isolate the effect of wildfire suppression, they ran five scenarios with varying intensities of firefighting. Moderate, high and maximum suppression assumed that the initial attack teams were on site within 4, 2 and 1 hours, respectively. With progressive suppression, crews simply monitor a low- or moderate-intensity fire until it starts to increase in intensity and then they go into suppression mode. Finally, the researchers modeled a zero-suppression situation.
After running the simulations thousands of times, the researchers found that aggressive wildfire suppression appears to cause large wildfires to burn more acres, and more areas experience high-intensity fire rather than the patchy kind of burning that occurs with smaller fires.
For years, fire researchers have bemoaned the “fire suppression paradox,” where suppressing wildfires in the present can merely make future wildfires worse by allowing a lot of forest vegetation to persist. But as a result of their findings, the UM researchers have added a new concept of “wildfire suppression bias,” where because smaller fires are squelched early, large fires end up being bigger because they burn the area that smaller fires should have burned.
There have always been some fires that burn big, such as the 1910 Fire. But because of suppression, those kinds of fires are now over-represented, because smaller fires are immediately put out. Thus the public perception of wildfire is also skewed only toward large fires.
The researchers use the analogy of the overuse of antibiotics.
“In our attempt to eliminate all fires, we have only eliminated the less intense fires (that may best align with management objectives such as fuel reduction) and instead selected for primarily the most extreme events (suppression bias) and created higher fuel loads and more ‘suppression-resistant’ fires (suppression paradox),” the researchers wrote.
In the mid-1960s, some federal agencies such as the National Park Service recognized the ecological role of wildfire and created a policy to allow fires to burn under certain conditions. The U.S. Forest Service was slower to follow. In 1970, Montana foresters pushed to allow wildfire to burn within the Selway-Bitterroot Wilderness and the results prompted a gradual shift away from the Forest Service policy of complete suppression. But during the recent pandemic, agencies slid back toward full suppression as a way to compensate for limited crews and over-extended resources. The UM research shows how that may backfire.
However, the researchers acknowledge that the Forest Service faces challenges if it tries to implement a more progressive policy of fire suppression. Internally, some forest managers will dismiss new research and continue to adhere to the traditional policy of suppression. Meanwhile, some members of the public distrust government agencies and will demand immediate action when fires are discovered. That attitude is exacerbated by the fact that more people keep moving into forested areas.
They also note the value of prescribed burns but say that prescribed burns should be augmented with progressive suppression to reduce the intensity and size of future wildfires.
“It may seem counterintuitive, but our work clearly highlights that part of addressing our nation’s fire crisis is learning how to accept more fires burning when safely possible,” said Philip Higuera, co-author and UM professor of fire ecology. “That’s as important as fuels reduction and addressing global warming.”
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.