FLAGSTAFF, Ariz. -- A controversial study that questions decades of forest ecology research has made headlines across the country. The study -- published earlier this year -- raised eyebrows especially in the west where forest managers have been trying to prevent severe wildfires for decades.
The U.S. Forest Service has spent millions of dollars trying to prevent large devastating wildfires by thinning the forests and setting smaller fires. These are called controlled or prescribed burns. But new research suggests a different solution -- just leave the forests alone.
In a paper published in the journal Global Ecology and Biogeography authors William Baker and Mark Williams from the University of Wyoming say they found evidence in historical survey data that suggests intense crown fires are one of the natural processes that maintain a healthy ecosystem. Baker and Williams were not available to speak with me for this story, so I had to turn to other experts.
Wally Covington runs Northern Arizona University’s Ecological Restoration Institute. Covington walked through a wooded area on the NAU campus and stopped to show a cross section of an old, old tree that he’d brought along.
"You can see where fire came through and scarred this tree," Covington said.
He pointed to the many tree rings and burn scars. That’s evidence of where this 300-year-old tree survived many low-intensity fires.
Covington said all throughout the western United States there's similar evidence that shows frequent but low-intensity fire. Then in the early 1900s the tree shows the fires stopped. That’s when animals were allowed to graze and eat up the fuel. It’s also when the Forest Service began to actively suppress most fires.
As a result, by the 1970s the forests had thickened, and wildfires across the west were getting bigger.
And so Covington along with nearly all forest managers in the country have spent the last few decades promoting a program of saving old growth trees, thinning smaller trees and allowing controlled burns to clean up the forests.
So he gets a bit frustrated when asked about Baker and Williams’ research. Covington said it flies in the face of more than a century of scientific findings and dozens of other published papers. Covington has talked to Baker.
"'You’re preventing us from restoring the land for future generations,’" Covington told him.
Baker drew conclusions from his research that suggested both low-intensity and high-intensity fires are natural. And we should allow some crown fires to happen.
Because Baker wouldn’t comment on his research, I turned to the editor of the journal in which it was published, David Currie. He said the manuscript, like all of their submissions, was reviewed by two anonymous experts in the field. They rigorously examined the method, the data and decided they were appropriate and fairly interpreted.
"That said it’s always possible that different reviewers might have a different view of the entire situation and might come to a different conclusion based on exactly the same paper," Currie said.
In northern Arizona -- a laboratory for fire prevention -- the evidence does point to a different conclusion. Forest Service Fire Ecologist Linda Wadleigh showed me how thinning and prescribed fire actually worked recently to save a neighborhood.
The few acres that have been thinned are what most ecologists would call healthy. When an intense crown fire hit this area last year, it slowed down and became manageable.
"Ponderosa Pine is very adapted to high frequency, low-severity fire," Wadleigh said. "I’m talking about flame lengths that are less than four feet. You and I could stand next to it with the proper equipment on and work with that kind of fire."
Wadleigh said in a different region, at a different elevation, a different species would be able to recover from a high-severity fire. Part of Wadleigh’s job is making recommendations to forest managers in northern Arizona. So she said she’ll take Baker and Williams’ study and add it to the large body of science on forest ecology.
"I have to take it all into consideration," Wadleigh said.
But she said you can’t take one type of fire regime that might apply in Montana and apply it to Arizona. It’s not a one-size-fits-all approach.