Science

A hellish combination of topography, weather, and fuel stirred the Oak Fire

Summer has more or less become synonymous with wildfire season across the Western United States—currently there are 93 large fires and burning through 3,116,631 acres in 15 states. Since the very beginning of the year, over 38,000 fires have burned across 5,571,855 acres, almost double the area aflame during the same period in 2021. 

This year has actually been pretty calm compared to some fire seasons. But one fire in particular has caught the headlines—the Oak Fire currently burning near Yosemite. Thousands have been forced to evacuate as the fire rages through a chunk of central California over half the size of Paris. On Saturday, California Governor Gavin Newsom declared a state of emergency in highly-affected Mariposa County and secured a FEMA grant for fire suppression resources. 

Compared to the Washburn Fire, which earlier this month threatened ancient Sequoia tree populations, the Oak Fire threatens human lives and infrastructure more directly—seven homes were ruined as of Monday morning, and by nightfall, 21 homes and 34 outbuildings were completely destroyed.

What makes this fire so devastating? The weather just really is that bad right now, says John Abatzoglou, climate expert at the University of California, Merced. “The last ten days or so in California and the Sierra Nevada have just been relentlessly oppressive in terms of heat,” he says. In Mariposa County, average daily temperatures haven’t been lower than 90°F since July 9, with temperatures expected to potentially creep into 100°F this weekend. 

“It has taken fire danger, as we measure it, from typical summer conditions to nearly off-the-charts conditions for this time of year,” Abatzoglou says. “That is saying something in a place like California.”

On top of the heat, the Oak Fire has an abundance of dried up plants to act as fuel. Parched plants that quickly light up can be found nearly everywhere, due to longer fire seasons,extreme dryness, and some of the worst drought conditions in recent years (California’s ongoing drought, arguably the worst in 1,200 years, is fueled largely by climate change). . 

This part of California hasn’t burned since 1924, meaning there’s about a century’s worth of fuel waiting to catch flame. “The link between climate change and Western wildfire is very clear at this point,” Daniel Swain, a climatologist at the University of California, Los Angeles said in a NASA release. “Climate change is causing long-term aridification and supercharging the intensity of shorter-term droughts in this region. It is drying out vegetation well beyond historically observed levels and greatly increasing the flammability of entire landscapes.”

Mariposa County also has incredible steep topography, which combined with unusual weather and an abundance of dry fuel makes for the perfect wildfire storm. Luckily, winds haven’t been too strong—which could cause the fire to billow and move even more quickly. The steep terrain, however, is creating its own gusts of wind, kind of like “opening up the flue in our fireplace” as Jeffrey Barlow, lead forecaster at the National Weather Service forecast office in Hanford, California, told the Washington Post

While the extreme fire burns, some have called upon President Biden to declare a national climate emergency. Former Vice President Al Gore told ABC News this week that the “survival of civilization is at stake,” although the actual efficacy of such a declaration is debatable. Often they make for symbolic moments—but not change in the form of climate action. 

When it comes to wildfires, regulating and preparing for them can be incredibly tricky. Prescribed burns and managed fires can help reduce the vegetation up for grabs on fire-prone areas. But after multiple prescribed fires got out of control, the Forest Service has stopped this type of management—leaving lots of fuel to be eaten up by wildfires. 

“I don’t know if a climate emergency is going to solve the [wildfire] problem because the problem is huge,” says Abatzoglou. “It’s going to take a lot of time to sort of dig our way out of the climate problem.”



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