The humble shrub that predicts a terrible fire season

“I think the risk of a wildfire this year will be about as high as it gets,” adds Swain. “And that’s pretty alarming considering what we saw in the last one a few years. “

In 2019, the Kincade fire burned nearly 80,000 acres north of San Francisco, and in 2020, a rare summer storm started hundreds of fires that covered with northern california in smoke. “This year, with the lack of rain and the amount of dead fuel left over from years and years of drought, California is still receptive to another fire season equal to, if not worse, than the one we have seen. Last yearSays Jon Heggie, battalion chief of the California Department of Forestry and Fire Protection, also known as CalFire.

With vegetation already so parched, accidental ignitions can turn into large flames. But the worst of the state’s fire season usually only happens in the fall, when the seasonal winds tear apart, causing wildfires at incredible speeds. This is what made the campfire of 2018 so deadly: The winds accelerated the conflagration through vegetation so quickly dries up that many residents of Paradise Town could not escape. Eighty-five people died.

Photography: Bryant Baker

There is a frustrating and often tragic aspect to fire science and to predicting the probability of ignition: researchers like Clements can use chamise and atmospheric modeling to warn when conditions will be ripe for an out of control fire in California, but they can’t tell or it will explode. In 2018, Clement says, dry fuel and forecast strong winds told him the fire risk was very high just before the camp fire. “I knew the day before there would be a bad fire,” he says. “We just didn’t know where this was going to be.”

Power company Pacific Gas & Electric later pleaded guilty in court to manslaughter charges related to the fire, admitting that its equipment had triggered it. According to Los Angeles Times, the utility had the option of initiating what is called a public safety power outage, or PSPS, to turn off this equipment, but did not do it. PG&E has since committed to to improve this PSPS program.

Part of what informs the PSPS decision is the wind and humidity forecast. But the other part is chamise: PG&E teams are sampling the plant from sites across northern California. All of that data goes into a Fire Potential Index, or FPI, that utility staff calculate every day, allowing three days for their territories. “Our FPI is actually quite sensitive to changes in the humidity of living fuel,” says Richard Bagley, senior meteorologist PG&E. “This is how it’s really important for us to really understand this piece of the puzzle.”

Climate change, of course, complicates this puzzle, creating the California wildfire crisis. never mind. The rains arrive later in the year, meaning seasonal winds have more time to start fires in a landscape that has been dehydrating since spring. And generally speaking, a warmer, drier atmosphere draws more water from the plants. Chamise therefore tells the story of a state in the grip of a decisive upheaval. “If you think about climate change and forest fires, it all depends on the humidity of the fuel,” Clements says. “We get drier, so we get more moisture from these plants and reduce the moisture in the soil.”

“Climate change fingerprints,” Clements adds, “are everywhere.”

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