California’s longer, riskier fire seasons usher in new era for public safety and environment
Scientists are confirming what many Californians already suspect: The wildfire season is becoming longer and more intense as our climate becomes warmer and more volatile.
Human-driven climate change has doubled the cumulative acreage burned by forest fires since 1984, according to a 2016 report in the journal of the Proceedings of the National Academy of Sciences.
In California, the acreage that burns annually has increased 500% since 1972, according to a study published in July in Earth’s Future, a journal that examines global environmental trends.
The trend has led to a new trope: the year-round wildfire season. Throughout much of the West and particularly in California, the thinking goes, there is no longer a fire season sharply defined by the desiccating fuels of early summer and the first autumn rains. Instead, our wildlands can now burn at any time, expanding the season from six or seven months to 12.
Yet the true situation is more complicated than that. It now seems assured that the North Bay fires of 2017 and this year’s Kincade fire aren’t outliers. They’re more likely harbingers of what then-Gov. Jerry Brown last year called “the new abnormal,” an era marked by more fires, bigger fires and increased threats to human life and property.
But the risk isn’t distributed evenly, and wildfire researchers and firefighters alike say appropriate responses will very depending on the region, land-use practices and other factors.
Further, the public needs to distinguish between different uses of the term “fire season,” said Marshall Turbeville, a Cal Fire battalion chief and the chief of the Geyserville Fire Prevention District. The state defines the wildfire season in legal terms, using weather and fuel conditions as metrics, Turbeville said.
“The start and ending is determined each year by declarations from Cal Fire, and (for the 2019 season) it ended on Dec. 9,” said Turbeville. “But the larger issue is the wildland fire potential season, and that definitely seems to be getting longer. We’re now seeing large fires occurring from late summer through early December. I’ve had 24 years in firefighting, and when I started out as a seasonal employee we’d typically get hired in early June and laid off in the fall. Now Cal Fire is hiring seasonal firefighters as early as March 1, and in some cases they’re not being laid off.”
Several years ago, said Turbeville, “We’d be doing winter preparation tasks such as pile and broadcast burning in late October. But that’s now when we usually have our biggest fires. So the reality is that the wildfire potential season - the time when we can see really destructive wildfires - is about nine months.”
Scott Westrope, the deputy fire chief for the city of Santa Rosa, agrees with Turbeville that the de facto fire season is lengthening, a fact that compounds operational and administrative challenges for firefighters. Not long ago, said Westrope, firefighting agencies could expect a multiple-month break between seasons, allowing for such things as administrative review, gear inspection and repair.
“Preparation typically starts as soon as the heavy rains begin, but that timeline has become compressed,” said Westrope. “For Santa Rosa at least, the fire season is literally yearlong. If we’re not actually fighting fire all year, the following season could literally begin in a matter of weeks, meaning that active training and preparation never stops.”
While both coastal California and the Sierra Nevada are experiencing increased wildfire activity, their seasons aren’t necessarily congruent and fire causes are often different. The Sierra typically sees a shorter season than coastal California because fire danger drops abruptly with the first snowfall, while the threat can linger much longer in coastal regions. Still, the fire danger in the Sierra quickly ramps up once the snow melts and the sun starts beating down.
“It’s clear that the Sierra’s fire season is lengthening,” Carmen Tubbesing, a doctoral candidate in fire science at UC Berkeley’s Department of Environmental Science, Policy and Management. “We’re seeing more days per year of red-flag weather. The prolonged droughts associated with climate change are killing more trees and drying fuels to an increasing degree, generally compounding the threat.”
In the Sierra, lightning usually accounts for most of the ignitions, Tubbesing says, while coastal region wildfires are mainly attributed to human-associated causes - damaged power lines, cars, lawnmowers and arson. The Sierra has a bigger fuel problem - millions of drought-killed conifers - than the coastal regions, but the Bay Area and Southern California have a greater dilemma in the spread of development into wildland: that is, very large numbers of people living close to open space that contains enough trees, grass and brush to burn fiercely.