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Home » What caused the California wildfires? The recurring crisis, explained

What caused the California wildfires? The recurring crisis, explained

The images and reports out of California this week are overwhelming: concurrent colossal wildfires laying waste to property and landscapes, freaky orange skies, massive smoke clouds, worsening air quality, more than 64,000 people forced to evacuate, and all of it compounding the risks of Covid-19.

If this feels like déjà vu, here’s why: Wildfires are growing more common and more severe in California. The most recent season of horror was 2018, which had 10 large fires that each burned more than 500 acres. Most infamous was the Camp Fire, which left 86 people dead in Paradise and caused more than $16.5 billion in losses, according to the German insurance company Munich RE.

This August was California’s warmest on record (as it was for five other states as well), setting the stage for the extraordinary streak of extra-large fires burning now. Five of the current fires are in the 20 largest wildfires in the state’s history: the August Complex (the largest blaze in state history as of Thursday), the SCU Lightning Complex, the LNU Lightning Complex, the North Complex, and the Bear Complex. As their names hint, these are megafires that gained size and strength when smaller fires combined into unified blazes.

The heat wave that preceded this terrifying swarm was not a blip. The weeks of arid, hot air that crisped out the forests and shrubs now aflame are part of a familiar pattern of extreme weather events: the climate crisis accelerating right in our faces.

As the climate heats up, many other states in the West, including Oregon and Colorado, are seeing larger, more devastating fires and more dangerous air quality from wildfire smoke. But California is at particular risk, both because its increasingly volatile weather may bring more droughts than other states and because it has more people and more buildings. Let’s walk through the details of how we got here.

A Butte County firefighter douses flames at the Bear Fire in Oroville, California, on September 9, 2020.
Josh Edelson/AFP/Getty Images

California’s forests have become tinderboxes

To understand why California is experiencing so many devastating fires year after year, let’s look at two basic forces at play.

The first is climate change. According to a 2019 paper in the journal Earth’s Future, California’s annual burned area has increased more than fivefold since 1972, which the authors attribute in part to a warming climate. The total annual area burned during summer fires is rising fastest, they note, though the climate fingerprint is getting clearer in the increase in areas burned in the fall as well.

climate and wildfire

Gov. Gavin Newsom’s Strike Force report on wildfires and climate change

California’s forests and shrublands have been subjected to wildfire pretty much forever; fire is a natural part of many of the state’s ecosystems and the Indigenous peoples of California set controlled burns to manage the landscape. What’s different now is that the season is getting longer, it’s gotten harder to manage the forest, and the fires are on average getting bigger and more destructive.

“Climate change is amplifying fire behavior and fire size,” Alan Ager, a researcher at the US Forest Service who studies how to manage wildfire risk on federally managed forests and other lands, told Vox in 2019. “Fire can travel larger distances” than in the past because there’s more fuel.

The basic recipe for a monster 21st century wildfire is this: Take hot air and no rain and moisture evaporating from trees, shrubs, and soil. After a series of these long, expansive, hot, dry spells, trees and shrubs will be transformed into ideal tinder to feed a fire. The bigger the area affected, the more available fuel. All you need then is a spark, which could come from a power line failure, a cigarette, or a firecracker.

Christina Animashaun/Vox

Climate models show that as temperatures continue to rise, the atmosphere and land in some regions, like California’s forests, will grow more arid. There will be more frequent and intense droughts, followed by intense periods of rain — a form of weather whiplash. This prompts the growth of thick underbrush, which then dries out in the subsequent droughts and becomes highly flammable kindling.

A newer phenomenon scientists are seeing in 2020 is wildfires that grow dramatically overnight because temperatures aren’t dropping like they used to. “One of the things we see with human-caused climate change is that the overnight lows are getting warmer,” said Matthew Hurteau, associate professor of biology at the University of New Mexico. “In the past, the sun sets, the temperature drops, the relative humidity goes up, and fire behavior dies down, and that’s when a lot of progress gets made in terms of fire suppression, because the flame lengths are shorter.”

But this year, the Bear Fire, one of the three fires that became the North Complex Fire, expanded by 100,000 acres overnight, destroying almost every structure in the 525-person community of Berry Creek, according to the Sacramento Bee. “That kind of fire growth, especially at night, that’s a climate signal for sure,” said Hurteau.

The second factor making the state more fire-prone is poor forest management.

In 2019, journalist Mark Arax published an extraordinary feature story on the Paradise fire, California’s most destructive fire ever. In it, he tells the tale of how, in the 1990s, the state’s timber industry came to be dominated by rampant clear-cutting. Varied, diverse forests, with patches of scrub and trees alternating, served as natural fire breaks. Wildfires came to them periodically, as is natural and necessary for regeneration, but they did not spiral out of control.

After a clear cut, forests are replanted as monocrops. There are no natural breaks, no variation, which makes them extraordinarily vulnerable to rapidly spreading fire.

And in the early 2000s, park rangers practiced a certain form of forestry management — prescribed burns, clearing brush, remediating clear cuts. But it fell out of favor as an increasingly large, paramilitary fire brigade took over. “As rangers joined up with the ranks of better-paid firefighters,” Arax writes, “their numbers dwindled to maybe 250, even as the number of firefighters inside the [Department of Forestry and Fire Protection] jumped to 7,000.”

Firefighters put out fires; they don’t do prescribed burns. But consistent fire suppression only increases the amount of dry, flammable material.

As this LA Times story reveals, California’s clear-cutting and forest mismanagement continue to this day.

Paul and Ronne Falgren look through the rubble of their home burned by the LNU Lightning Complex Fire in Lake Berryessa, California, on August 31, 2020.
Jane Tyska/Digital First Media/East Bay Times/Getty Images

More and more people are building (and rebuilding) in fire-prone areas

California also has a housing crisis, born largely of the fact that wealthier urban residents refuse to allow more housing to be built in urban areas, near jobs. Consequently, as more residents stream into the state, the price of existing urban housing stock rises and development sprawls outward. More and more of that development is being pushed into the “wildland-urban interface” (WUI), where wildfires are more frequent and more difficult to fight.

Some 11.3 million people — more than any other state with regular wildfires — live in the WUI in California. That’s 30 percent of the state’s population living near a lot of potential wildfire fuel. And more than 2.7 million Californians currently live in “very high fire hazard severity zones,” areas where the population is expected to keep growing. (Cal Fire is currently updating its hazard zone maps and expects to roll out new ones by 2021.)

Again, California is not alone. A 2018 study in PNAS found that between 1990 and 2010, the WUI was “the fastest-growing land use type in the conterminous United States.” This is happening in lots of states.

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