In the Sierra Nevada, private lands used for logging are more likely to experience high-severity fire that devastates forest ecosystems compared to public lands like National Forests.
It’s a fact that’s been known for years — but what exactly causes this discrepancy has remained elusive.
Consequently, the factoid has served as fuel for the longstanding California debate of “who is to blame for our wildfire problem?” while providing little insight for forest managers hoping to address it.
A new study published Wednesday finally offered some answers. By studying detailed data around Plumas National Forest north of Tahoe both before and after a series of devastating wildfires burned 70% of the land in just three years, researchers identified the common practices responsible for increased severity.
They found that when a fire ripped through, private timber lands were about 9% more likely than public lands to burn with such intensity that virtually no trees survived.
When the scientists looked at what prefire forest characteristics resulted in severe fire, they found that dense groups of evenly spaced trees were largely to blame. It’s the exact kind of forests timber companies often plant to intentionally harvest a few decades down the road.
“It allows the fire to essentially gain a bunch of momentum and start exhibiting much more extreme fire behavior than if it’s encountering road blocks every once in a while: open areas or meadows or areas with really big and more resilient trees,” said Jacob Levine, postdoctoral fellow at the University of Utah and lead author on the study.
While California’s forests are adapted for frequent, low-intensity fires that clear out the forest floors and promote regeneration, high-intensity flames can decimate ecosystems so much so that they may never recover.
Although the study focused on one forest in Northern California, it has implications across the Western U.S., where this kind of “plantation”-style logging is common.
The conditions in Plumas National Forest, “I’d call them very typical for at least Oregon, Washington and California,” said Scott Stephens, UC Berkeley professor of fire science and co-author on the study. “These are places that are more productive, they have more precipitation, they grow trees faster.”
For the scientists, the results emphasize just how much work California still must do to address its wildfire problem. They hope the results, instead of vilifying logging companies, can help spur a conversation about what forest managers can do better.
“If you want to grow timber in the state, contribute to the economy, contribute to home building — all those are laudable goals,” Stephens said. “I think you’ve got to think about, ‘Well, how am I going to do this in the fire environment of today or the future?’ ”
And while public lands are less likely to experience severe fire than timber lands — with a 57% probability of experiencing high-severity fire, compared to timber lands’ 66% — government forest managers aren’t necessarily doing a perfect job either, experts say.
While timber companies’ approaches tend to be too “hands-on” — bulldozing over the natural ecosystem (sometimes literally) — the U.S. Forest Service still tends to be too “hands-off,” experts argue: National Forests are still lagging behind on much-needed prescribed burning and mechanical thinning work (or “forest raking” as the president likes to call it).
The U.S. Forest Service allows logging on about a fourth of its land through agreements with private companies (which President Trump aims to significantly increase), but it has moved away from the practice of planting dense, evenly spaced “pines in lines” plantations.
The forest-fire blame game fueled by these differences in approach has gone on for decades.
After the 2007 Moonlight fire scorched 65,000 acres, including in Plumas National Forest, both the federal and state governments filed lawsuits against California’s largest timber company, Sierra Pacific Industries, alleging the fire was started by a subcontractor’s bulldozer that hit a rock and created a spark.
The company initially settled with the federal government while not admitting any wrongdoing, but, through a lengthy legal drama now living on as Sierra Nevada folklore, the company’s lawyer petitioned, alleging that the federal government had concealed the fact that its own fire watch lookout was caught away from his post reeking of marijuana and peeing on his feet.
The Supreme Court ultimately declined to hear the company’s appeal, while a lower court eventually ordered Cal Fire to pay out $15 million for fraud and withholding evidence.
In recent years, the federal and state governments and private industry have increasingly begun to cooperate on an active management strategy.
In 2021, Gov. Gavin Newsom created a task force to develop such a plan. It set a goal of practicing active management, primarily through mechanical thinning and intentional fire, on 1 million acres every year. Both the Forest Service and private timber companies are active participants.
Stephens and Levine hope their work can help forest managers work smarter, not harder.
The team analyzed data from planes that used lasers to create a 3-dimensional map of the forest — down to individual trees — in 2018 before the major fires that burned the majority of the land. They then looked at satellite data taken after each fire measuring the resulting severity of the burns.
The team found that the biggest indicator of how severely a fire burned on one plot of land was how severely it burned on plots next door. This made sense to the researchers: Fire is contagious, meaning a high-intensity fire with a lot of energy and momentum is likely to continue at a high intensity.
This can also create a spillover effect. Areas susceptible to high-severity fires, like private timber lands, can lead to high-severity fire in surrounding better-managed areas as well, typically up to a little over a mile away.
The second most important factors were how tightly-packed the trees were and how hot, dry and windy the weather was on the day of the fire. The effects also compounded: The worse the weather, the more forest density served as a predictor for fire severity.
The team also found that “ladder fuels” between the low-lying ground vegetation and the canopies of trees — which can help a fire climb high into the canopy — contributed to fire severity. Clustered trees and open spaces in the canopy, meanwhile, resulted in less severe fire.
Tree density, the most significant indicator related to forest management, is fundamental to timber’s business: It allows companies to produce more wood on the same amount of land. But Levine still sees a way forward.
Moving away from plantation-style logging by planting trees in irregular, clustered patterns and staggering planting over years to create a forest with different-aged trees can make sure tree crowns aren’t all perfectly aligned for a fire to rip right through.
Previous research from Stephens has repeatedly shown that mechanical thinning and prescribed burns are incredibly effective at reducing high-severity fire risk while also improving forest health and preserving biodiversity. (Notably, the researchers couldn’t explore the effects of ground vegetation in this new study, since the laser data struggled to detect it.)
There are already several examples of timber companies that have moved away from plantation-style logging in favor of more natural, fire-resistant forests. And, while these practices can be more expensive in the short term, Levine is still optimistic they can gain traction as research increasingly shows their effectiveness.
“Timber companies are also invested in their forest not burning down,” he said. “That’s bad for business, too — if you plant the plantation and then 30 years later, before it gets to the size that it becomes profitable, it goes up in flames.”
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