Before the California wine country fires roared through vineyards and neighborhoods, they first blazed in the forests and shrublands in the rugged coastal foothills. “They started well into the wildland areas and then burned into heavily populated areas; places people would never have expected wildfires to come through,” says Lynne Tolmachoff, spokeswoman for Cal Fire, the state fire agency.
So far, the fires in Northern California have killed 42 people and destroyed several thousand homes. Strong winds and low humidity have helped make these fires among the most damaging in state history. The deadliest was the Tubbs Fire in and around Santa Rosa; 22 people died. Embers from that fire were carried in the wind and showered houses, spreading the fire rapidly in residential areas, according to Daniel Berlant, an assistant deputy director of Cal Fire.
But the condition of forests and shrublands also contributed to how severe the fires were when they approached urban areas, says Brandon Collins, a research scientist at UC Berkeley. The fires gained intensity as they ran through mixed hardwood forests and slopes covered with chaparral, manzanita and other shrubs. Chaparral “is designed to burn pretty hot,” says Jeffrey Kane, an associate professor of fire ecology at Humboldt State. And both forests and shrublands were overgrown, choked with underbrush and small trees that provided a continuous source of fuel as the fires moved across the hilly terrain.
“Wind alone will make even a grass fire spread quickly, but it would not have the head of steam that this one had to penetrate so deeply into the urban areas,” Collins adds. “You can’t just say it’s the wind because you have to have the fuels, too.”
That fuels buildup is largely the result of firefighters snuffing out almost every wildfire in the area for many years. While a few big burns in the 1960s and 1980s covered some of the same footprint as this month’s fires, “we’ve been pretty successful taking fire out of there,” Collins says. “To every extent possible they’ve suppressed fire there for decades.”
Northern California typically has four to six months of dry weather in a row, which creates the potential for fires. But with some exceptions, the region has been able to keep fire in check by aggressively suppressing blazes. These recent fires, and the 2015 Valley Fire, show that strategy may no longer fit the challenge. The Valley Fire destroyed or damaged more than 2,000 homes and other structures in Lake County. “If you start piecing these things together, you realize these aren’t just one-offs,” Collins says. “The spread is so quick that no crew can make an impact; they’re growing faster than we can do anything to control them.”
Across the West, climate change is lengthening wildfire seasons and contributing to hotter and drier conditions that make landscapes more prone to high-intensity blazes. In a groundbreaking study published last October, scientists estimated that nearly half of the acreage burned in Western forests over the last three decades could be attributed to human-caused climate change.
Experts say that it’s already clear that to protect communities in the future, fighting fires will not be enough. Communities near forests and shrublands need to cut down some trees and remove the underbrush or use controlled burns. “Where you have dense communities adjacent to wildlands, these kinds of events are going to happen,” Kane says, unless landowners, local governments and others actively work to reduce fuels and build with fire resistant materials.
Cal Fire staffers are now trying to determine how these recent fires were ignited and what made them so destructive. “We have investigators out there,” Tolmachoff says. “Then we’ll work from there to decide what we could have done to prevent, stop or slow them.”
One strategy might be reducing the overgrowth in forests not just close to homes, but far away from populated areas as well. The Wine Country blazes traveled from distant wild landscapes and jumped across supposed barriers like roads and strips of bare land. Northern California is not unique in needing this remedy, says Collins: “I think this could very well apply to heavily forested areas of Sierras and Rocky Mountains; we’re seeing large fire growth everywhere in the Western United States.”
Correspondent Elizabeth Shogren writes HCN’s DC Dispatches from Washington. Follow @shogrene
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