Arizona’s largest wildfire on record is the 2011 Wallow Fire.
That fire burned across more than half-a-million acres in the White Mountains and into New Mexico.
But the Wallow Fire wasn’t as unique as previously thought, says researcher Chris Guiterman with the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder.
Guiterman says he and other researchers looked at tree rings all around the Wallow Fire burn scar, looking for evidence of fires going back hundreds of years.
“So we could estimate the acreage of fires in each year from 1650 right on to 2023. The Wallow Fire is one of the largest. It's exceptional. It's quite large, but we found three other years that had fires that were at least as big, and potentially larger than the Wallow Fire was,” Guiterman says.
Guiterman says they also found dozens of low-intensity fires that often burned nearly 200,000 acres.
Then came a hundred-year span when the federal government worked to put out every fire quickly.
“The really predominant pattern is that these extensive wildfires were burning quite commonly every 20 years in that landscape, and that has been completely missing since 1900,” Guiterman says.
He says those blazes would have burned at a low intensity, staying mostly on the ground and consuming grasses, needles and smaller trees.
That’s a far cry from the modern conception of megafires consuming stands of trees in catastrophic blazes.
Guiterman says, as land managers now attempt to return ponderosa pine forests to a more natural state by using prescribed fire, their findings suggest “burning it once and leaving it is not restoration.
“Historically, we did have some pretty extensive burning, and we could have that extensive burning fairly frequently,” Guiterman says. “It was really a central process in this forest. Just like rain, just like oxygen, the forest needs to burn and have that fire in there to kind of keep everything going.”
And Guiterman says, rather than a new phenomenon, the study shows that Southwestern megafires may have been almost as regular as the monsoon rains themselves.
