How the drought fueled California’s wildfires.

How the End of the Drought Likely Exacerbated the Deadly California Wildfires

How the End of the Drought Likely Exacerbated the Deadly California Wildfires

The state of the universe.
Oct. 10 2017 4:59 PM

How the End of the Drought Likely Exacerbated the Deadly California Wildfires

Lush grasses flourished in last winter’s deluge—and then dried out quickly to provide fuel.

171010_SCI_caliFires
Fire consumes a barn as an out-of-control wildfire moves through the area on Monday in Glen Ellen, California.

Justin Sullivan/Getty Images

Wildfires have been raging in California wine country since Sunday night, with 17 blazes quickly claiming more than 100,000 acres of land, some 2,000 buildings, and at least 15 lives. Local papers characterized the charred remains as “hellish” and devastating, and the pictures are hard to stomach.

How did these fires form and spread with such a vengeance? Didn’t the California drought finally just end? Is this what climate change looks like? Like any aggressive natural disaster, there will be careful and painstakingly slow analysis of this devastating dispersal of flame. But in the meantime, a couple of experts explained how the drought ending actually seems to have made California more fertile ground for such a disaster.

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Let’s take a couple steps back. We’re currently in wildfire season, which stretches from roughly May to October, until rains come in the fall. While that is not as well-defined as hurricane season, it does mean wildfires are common in California and neighboring states during this time. That’s because the region’s summers create the windy conditions and low humidity that prime the area for forest fires, transforming usually wet vegetation into dry fuel and dramatically exacerbated the flames.

As Stephen Pyne, author of numerous books on fire and environmental history, explained, this year, an abundance of vegetation resulting from the region’s wet winter is likely responsible for the intensity of the recent blaze. In April, California Gov. Jerry Brown declared an end to his state’s historic drought—after six years, unprecedented winter storms had refilled the state’s reservoirs and caked the Sierra Nevada in snow. The winter storms also brought the state’s moribund vegetation back to life, to the relief of many Golden State residents. Now, though, those grasses, needles, and other plants are coming back to bite residents. “When you have wet years, you can build up all the fine fuels, the shrubs, the needles, and all the stuff,” Pyne said. When they dry out in the fall, he says, “that’s what makes for all the fast-moving fires.” (Of course, dry conditions also exacerbate forest fires, leading to California’s Catch-22 situation. “Whether it’s exceptionally wet or exceptionally dry, you’ve got the material for a fire in California,” Pyne said.)

Still, the verdant post-drought landscape isn’t enough to explain all 17 fires raging right now, says Eric Knapp, a research ecologist with the U.S. Forest Service. While the greenery may be partially to blame, he thinks the winds are much more important. Every fall, the so-called Diablo winds sweep into central California toward the ocean, encouraging fires to spread faster than they would normally.* In the past few days, gusts of 70 miles an hour have been recorded, spreading the flames not just in the lush undergrowth Pyne described but also in chaparral and wooded forests.

Weather’s role in the storm is clear, but when it comes to the question of whether this event is linked to climate change, answers are hard to come by. Attributing a single event to climate change is always difficult, but fire’s near omnipresence in California makes it that much harder. Still, Knapp says he’s disinclined to link this event to climate change, given the Diablo winds have remained consistent—and consistently troubling. But, Pyne says, climate change is still a known driver of conditions that exacerbate forest fires. Western wildfires have been on the rise since the 1980s, and as temperatures rise and the driest parts of the world get even drier, some are predicting that, one day, for some parts of California, wildfire season will never end.

*Correction, Oct. 11, 2017: This story originally misstated that Diablo winds blow from the ocean. They blow toward the ocean. (Return.)

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Eleanor Cummins is an intern at Slate. Her reporting interests run the gamut of science. Follow her on Twitter.