But Dr. Johnston’s research, in eastern Oregon, has shown that even thinning alone can be beneficial, at least for a time until there is substantial regeneration of trees and shrubs that increases the risk of a larger fire.
That research is part of a large body of work throughout the West that shows that forest treatments can work to reduce fire intensity. But the view that such treatments are beneficial is not shared by everyone.
Dominick DellaSala, chief scientist with Wild Heritage, an organization that seeks to keep primary forests intact, says that thinning, especially, is oversold as a treatment and that there are benefits to wildlife diversity in older, untouched forests — even after wildfire sweeps through them.
“It all depends on how we see the forest,” Dr. DellaSala said. In an untreated forest, what some might see as fuel, others “see as incredible habitat for wildlife because it’s a mosaic of different burn severities that is extraordinarily biodiverse.”
And preliminary research by a colleague, Bryant Baker, of Los Padres ForestWatch, a conservation group in Southern California, found that much of the forest land burned in the Bootleg fire had in fact been treated, mostly through thinning or clear-cutting but occasionally prescribed burning, as far back as the 1970s.
“This area was really heavily managed for decades,” he said.
Proponents of thinning and prescribed burns acknowledge that treatments won’t necessarily slow every fire, especially as fires grow larger and more ferocious in a warming world. But they say the evidence shows treatments are effective.
“It’s not rocket science,” Dr. Johnston said. “It’s the right thing to do, and it works.”