USA — In the vast ponderosa pine forests that stretch across northern Arizona, decades of research have shown that low-severity, frequent fires were the historical norm.
But a new study out of the University of Colorado cautions that those same assumptions dont apply to higher elevation, mixed conifer forests like the ones blanketing the upper reaches of the San Francisco Peaks above 9,000 feet. The study showed that the raging, stand-replacing fires that have become the worst nightmare of communities across the West were actually the natural fire regime in wet, mixed conifer forest types.
Its a conclusion that requires a change in mentality for people who think that ecological restoration looks the same across the forest, the researchers said. In many areas, a forest that may look like a tinderbox is actually in its natural state, said Thomas Veblen, a CU geography professor and one of the studys co-authors.
We shouldnt be blaming land managers and a history of fire suppression as the cause for those being fire-prone forests, Veblen said.
Thats the case in Arizona, too, said Wally Covington of Northern Arizona Universitys Ecological Restoration Institute. The animals that make their homes in wet, mixed conifer forests need higher severity crown fires to clear out trees and create pockets of different-aged fuels within a forest, Covington said.
Some people say we need to restore these forests to open park-like conditions and frequent fire when in fact that wouldnt be restoration. That would be introducing a fire regime that’s unprecedented in that forest type, he said.
The forest that hikers see as they follow the Humphreys Peak Trail, for example, looks much the same as it would have before fire suppression efforts began, Covington said.
That’s because huge fires historically ripped through the forest only once every 100 years or more, which means fire suppression practices that began in the early 1900s havent had time to fundamentally alter the fire regime, Veblen said.
Reinstituting fire into the landscape is also more complicated in these higher elevation, mixed conifer zones, Veblen said. The natural fire regime wiped out 60 percent of trees or more, but thats not compatible with the current land uses. Homes, watersheds and recreational areas would potentially be destroyed if these types of fires were reintroduced everywhere they once reigned, he said. Efforts like forest thinning that are meant to reduce the potential of severe fire are necessary to protect places of value, but those techniques arent restoring the forest to its natural state.
We should not be trying to convince the public it would be the same as restoration, Veblen said.
Managing Mormon Mountain
That dynamic is playing out right now as the Forest Service pulls together a plan to deal with the threat of wildfire in Flagstaffs watersheds. Just over 200 acres of wet, mixed conifer forest blanket Mormon Mountain south of Lake Mary, one of the main focus areas of the Flagstaff Watershed Protection Project. The forest, a rare type in Arizona, is thick with white fir, Douglas fir, scattered aspen patches and occasional ponderosa pine trees. Its also home to several breeding pairs of Mexican spotted owls.
Managers considering how to deal with the threat of wildfire in the area recognize the challenge of reconciling the competing interests of restoring the mixed-severity fire regime that existed in this forest type, reducing high-severity wildfire risk in the watershed and preserving habitat for the Mexican spotted owl. What they came up with was an array of recommended treatment options that include burning piles of dead and down materials and hand thinning, but would fall short of returning this part of the forest to its historical fire regime. Higher-severity fires arent compatible with the projects goals of protecting soil resources and the wildland urban interface, the Forest Service’s report said.
Thus, for those areas, the proposed treatment approach is more geared toward fire-risk reduction than true restoration, it said.
In the ponderosa pine forests that make up the majority of the landscape around Flagstaff, the goals of mitigating fire risk and forest restoration are much more compatible. Frequent, lower-severity fires were common before the era of fire suppression, so thinning and prescribed fire mimic those historical patterns.
Fire game changing fast
Climate change throws an entirely new variable into the wildfire equation. The CU study recognizes that extreme weather conditions that have set the stage for the huge fire years in the past are only increasing. Climate change projections show that extreme years that present conditions ripe for large fires will be normal weather conditions in as few as 30 or 40 years, Veblen said.
As warming continues its becoming a whole new ballgame, he said.