California’s fire season hasn’t turned out to be as bad as some feared this year. In fact, forest managers say that certain kinds of fires — the “good” fires — were sorely lacking.

Sierra Nevada forests are adapted to low-intensity fires that clear the underbrush and prevent trees from getting too dense. After a century of fire suppression, many forests are overgrown, which can make catastrophic fires worse.

So forest managers are piloting a new policy designed to shift a century-old mentality about fire in the West.

The idea is to let naturally-caused fires burn when they aren’t a threat to homes or people. But actually making those decisions on the ground isn’t easy in a crowded state like California.

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Decisions on the Front Line

Today, the U.S. Forest Service allows some fires to burn on a case-by-case basis, as in early September, when forest managers got reports of smoke in the Sierra National Forest, south of Yosemite, after a dry lightning storm rolled through.

“The fire was really small at that point,” says Sarah LaPlante, the forest ranger on duty at the time. “It was probably about a quarter of an acre.”

It was dubbed the Crown Fire and LaPlante had to make the call about how to handle it.

“We didn’t put firefighters right on the line trying to stop the fire right where the fire is,” she says. “We can actually let the fire burn in a controlled way.”

The fire was extremely remote and the weather was cooling off, so she gave the order to let it spread, keeping a close watch.

“It wasn’t torching trees,” she says. “It was just cleaning the forest floor. Getting rid of all of that over-accumulation of dead, woody debris.”

It was exactly the low-intensity fire that LaPlante wanted to see. Around 800 acres have burned so far. Winter rains are expected to put the fire out in a couple weeks.

But being on the front lines of those decisions is never easy.

“It’s something that you take really seriously and there is some level of nerves,” LaPlante says.

Very rarely, these decisions go wrong.

Losing Control

Four years ago, rangers let a fire burn in Lassen Volcanic National Park. But the winds picked up and the fire spread thousands of acres toward the community of Old Station, an hour from Redding.

“Smoke was so heavy here ’cause it was blowing our direction,” says John Wallace, a restaurant-owner in Old Station who got ready to evacuate. “It was a scary situation.”

Luckily, the town was spared, but residents were angry and congressional hearings were held to investigate.

“Just the fact that they let it burn and get away from them,” Wallace says. “I mean, anytime something affects you that way people get upset.”

Near-disasters like that make forest managers hesitant to let any fire burn. And scientists say that only makes things worse.

California’s Fire Deficit

“So these are collections of fire scars from all over,” says fire scientist Scott Stephens, pointing to cross-sections of old trees inside his lab on the UC Berkeley campus.

“You can see each of these small black marks that are recorded in the wood, in the tree rings, are actually a past fire that the tree survived.”

The rings show that this centuries-old Pondarosa Pine used to survive low-intensity fires every six to twelve years. Those fires kept young trees from growing up to crowd the forest.

Today, forests in the Sierra Nevada are typically much denser than they once were, which can fuel catastrophic fires like the Rim Fire in Yosemite three years ago. Stephens says today there’s actually a fire deficit.

“It sounds crazy, but if you think about how fire used to work the land, millions of acres burned every year,” he says. “But you didn’t have things like the Rim Fire that actually causes a 20,000-acre patch of forest to completely die. No living trees for miles.”

Stephens clarified that in those patches, 95 percent or more of the trees died, making it difficult for the forest to regenerate.

That’s the legacy of Smokey Bear, and it hasn’t been easy for the Forest Service to change that legacy.

Changing the Default

“We have a better understanding of the role of fire now as an agency and probably as a society,” says Alan Taylor, a fire planner with the U.S. Forest Service.

For the first time in decades, the Forest Service is changing its fire suppression policy in three national forests in the Sierra Nevada. The Sierra, Inyo and Sequoia National Forests are piloting this new approach, as part of an update to their forest management plans.

The agency is creating fire risk zones by using computer models to analyze the terrain, type of forest and possible weather scenarios.

Some zones, near towns and roads, are protected, and fires there would be put out. But in another zone, covering 40 percent of the land, rangers would have to answer a question.

“If it’s a lightning-caused fire, why are we putting it out?” says Taylor.

This changes the default. Before, rangers had to make the case for letting a fire burn, but now, they’d have to justify putting it out if there’s no danger to people or homes.

“It’s going to take time, but we’re trying to put the tools in the deciders’ hands to start working toward having fire back in its natural role in these ecosystems,” says Taylor.

There’s a downside: more fire means more smoke and the Central Valley already has some of the worst air quality in the country.

“It probably will be smokier at times than what we’re used to,” Taylor acknowledges. But he says the smoke from low-intensity fires is easier to manage than smoke from catastrophic fires.

“The fires are coming one way or another,” Taylor says. “How do we want them to be? If we keep putting them out and the fuels keep growing, eventually it gets to the point that you can’t put it out.”

“It’s not going to be simple and it’s not going to be completely predictable,” says Stephens. “But I know one thing for certain. If we continue to have that backlog of forests that are in terrible shape, I call that a freight train having a wreck.”

If the Forest Service’s new approach encourages fire in California forests, it could be adopted by other forests across the West.

Editor’s note: A line was added to clarify the extent of tree mortality in the Rim Fire.