To prevent another Sierra inferno, thin and clean forests

If a transcendent lesson is emerging from the Rim Fire, it’s this: we need to manage our forests aggressively, thinning thick stands of young trees and clearing deadwood on the forest floor. Doing so would reduce fuel in second-growth and third-growth coniferous forests—the kind of fuel that has driven the Rim Fire to become the fifth largest wildfire in the history of the state.

And it would be well worth the cost.

That, at least, is the conclusion of Scott Stephens, the Cal associate professor of fire science whose four-person crew was surveying the Rim Fire area until they were forced to evacuate by the flames. He was there seven weeks ago and it was obvious the area was ripe for a catastrophic blaze. As he observed in an email, “…stumps (were) evident from past harvesting, (and there were) about 400 trees (to the) acre, dominated by Douglas fir and white fir with diameters around 6-15 inches, and very heavy surface fuels everywhere because of fire suppression…”

Such a forest, Stephens and most fire scientists agree, is a forest destined for incineration. As we noted in an earlier post, the Sierra forests encountered by the first Euro-American explorers, and by surveyors as late as the early 1900s, were composed of extremely large, mature, widely spaced trees. There were only a few trees per acre, not 400. And they measured from four to six feet in diameter, not six to 15 inches. They were resistant to fire because there was no “fuel ladder”—unlike today, where there is an abundance of fuels at every level, from the forest floor through the canopies of the tightly-packed trees.

Fires that did kindle in these ancient forests usually meandered around on the ground a bit before finally dying out, doing far more good than harm. They reduced fuels, harmful insects and microbes, and they return nutrients—primarily potassium and calcium—to the soil.

Today, vast areas of the Sierra are cloaked with heavy growths of small conifers—“doghair” stands, in logger’s parlance. And as we now see, these burn with a fierceness that almost beggars belief. Clear-cut logging followed by over-zealous fire suppression are to blame. And climate change only exacerbates the forests’ flammability.

But there’s a way out of this quandary, Stephens says: It will just take a lot of money and perhaps more political good will than exists in Washington. What’s needed is a solid commitment to fuel reduction on a landscape scale: thinning trees in the emergent forests, and disposing of the heavy burden of “slash,” or dead wood, on the forest floor.

Such efforts, accomplished through either “mechanical” means (hand tools and heavy equipment) or proscription fire, could ultimately replace our highly flammable doghair forests with fire-resistant open stands of big, magisterial trees—the forests of yesteryear.

“I believe that the climate is drying out forests earlier, and temperatures are up,” Stephens emailed us. “However, if fuels treatment had been used in (the Rim Fire) area we would not have had the tree mortality that has occurred. I talked to (staffers) at the (U.S. Forest Service) Groveland District about two months ago, and they had two fuels (reduction) projects ready to go in the Rim Fire area, but no funds to implement them. My view is that unless we get ahead of the fuels/restoration problem in forests that experience frequent fire (such as the Rim Fire area, which burned off in 1987), wildfires influenced by climate change will burn at severities and spatial scales that will not conserve forests in the future…”

That is to say, we need to reduce fuels in our coniferous forests ASAP, before they disappear entirely. As Stephens noted in an earlier post, such a transition wouldn’t necessarily be all downside: Many of the areas in the Sierra subject to frequent fire could be expected to eventually convert to oak woodland, which is inherently resistant to catastrophic fire and contains significant ecological value. Still, the chances of reclaiming the old-growth coniferous forests that once dominated the Sierra would be lost—an unmitigated tragedy no matter how you parse it.

It’s an assessment apparently shared by both government agencies and folks who live in the woods. Dick Fleishman, a U.S. Forest Service forest restoration assistant team leader based in Prescott, AZ, gave us his general take on fuels management while manning the phones at the Rim Fire media command post.

He said he couldn’t speak to the Sierra, “but it (fuels management) has worked in the past in other places. I’m working on a 2.3 million acre forest restoration project in Arizona, and fuel reduction isn’t so much a component of what we’re doing, but an objective. At the end of our work, we hope to see fuels reduced in the existing forest—and a forest that produces less in the way of heavy fuel loads as it grows.”

Responding a few days ago to our earlier post, @WillowPolson tweeted “Anybody with eyes in a ‘penny pine’ plantation can see that. I live next 2 one, been asking 4 thinning 4 years.”

Short-term, Stephens is particularly concerned—perhaps mournful is a more appropriate word— about the area he and his crew were surveying prior to the Rim Fire. “This site…(had) many remnant old-growth mixed conifer trees, including sugar pine, incense cedar, ponderosa pine and Douglas fir with diameters in the four-foot range,” he wrote in his email.  “I think this whole place is now gone, and I will get back in once things cool down to check it out.  The loss of these old trees is a big deal.”

As he intimated, some fuel reduction projects have been carried out in Yosemite National Park and in the national forest lands surrounding the park. It would be logical to assume the woodlands that had been so treated would fare better than untreated areas, but the data is not yet in.

“I am afraid we won’t know this for a month or more, until the remotely sensed data is analyzed,” Stephens wrote. “I am looking for this data as well.”

For more details on the importance of fuel-reduction treatments in western forests, check out this paper Stephens and Cal co-authors published in the journal BioScience.

—Glen Martin

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I read this post while finding searching for data about vegetation diversity. I do agree that we need to manage our forests aggressively, thinning thick stands of young trees and clearing deadwood on the forest floor. Candy Swift

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