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California’s recurring wildfire problem, explained

The state’s weather is becoming warmer and more volatile due to climate change. And there are more people and buildings.

A burned residence smolders from the Bear Fire, part of the North Complex Fires, in Butte County, California, on September 9, 2020.
Josh Edelson/AFP/Getty Images

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.

houses in the wui Gov. Gavin Newsom’s Strike Force report on wildfires and climate change

But it’s particularly concentrated in California, where a million houses were built in the WUI during those same years. In Mother Jones, Jeffrey Ball has a feature story on the state’s terrible land use policies, which encourage sprawl, and specifically building (and rebuilding) in fire-prone areas, in a dozen different ways, including subsidized insurance. (See also this piece in MIT Technology Review by James Temple.)

A recent study by Ager and colleagues found that 1,812 communities in the western US could be significantly impacted by future wildfires. Of the top 20 most exposed communities on the list, 14 were in California.

Add all this together — increasing heat from global warming, several years of unusually high winds and low humidity, poor logging practices with fewer preventive burns, more people living on forested ridges and hills in remote, fire-prone areas — and the result is disaster.

Why California can expect wildfire season to get worse

Parts of Northern California and the Sierra Nevada can expect to see the most fire activity directly linked to human-caused climate change in the coming decades, according to the Earth’s Future paper.

But “you can throw a dart anywhere around Los Angeles and San Diego and you will hit an area with significant fire potential,” too, Chris Keithley, research manager for the Fire and Resource Assessment Program at Cal Fire, said.

And there’s a huge mismatch, Ager’s study found, between the increased wildfire threat and how cities are planning future development.

The state’s population is also growing, leading to a significant overlap between the areas of high fire risk and areas with a growing population density, as you can see in these maps from a 2014 study of population trends in California projecting out to 2050:

A map showing population density growth projections (left) and a map showing fire hazards.
Mann et al./Land Use Policy

The study estimated that by 2050, 645,000 new houses in California will be built in “very high” wildfire severity zones.

Just as it’s time to consider retreating from the coasts because of sea level rise, it may be time to consider encouraging people to retreat from some of the riskiest fire-prone areas.

“I think planned retreat should be part of a suite of options,” said Paige Fischer, a social scientist who studies wildfires at the University of Michigan. So far, though, the state has done little to discourage new construction in high-risk areas or encourage people to move out of harm’s way.

In response to the billions of dollars in losses from the California wildfires of 2017 and 2018, insurance companies are now beginning to refuse to renew fire and homeowner liability insurance and hike rates for homeowners in fire-prone areas, the New York Times has reported.

But forcing people to move is an especially tough ask in California, given the housing crisis. Many Paradise residents who lost their homes in the Camp Fire had moved there to escape the unaffordable rents and home prices of the Bay Area.

The federal and state governments have increased funding for fire suppression and managing fire fuel like the millions of dead trees on public and private lands, but much more is needed.

“The thing that gets missed in all of this is that fires are a natural part of many of these systems,” said Matthew Hurteau, the University of New Mexico professor studying climate impacts on forests. “We have suppressed fires for decades actively. That’s caused larger fires.”

More prescribed burning could help limit potential megafire fuels, but many communities oppose it because of the short-term smoke risk. “Fuel management efforts need to be substantially increased,” Ager agreed.

That responsibility falls largely to federal and state agencies like the Forest Service that manage public lands. People who live in high-risk areas can also do more to manage the land and structures on their private property, for instance reducing flammable vegetation around homes and using fire-repelling building materials, Fischer said.

Climate change demands both immediate action to reduce emissions and immediate threats, and also long-term adaptation to a more hostile climate. California is a leader on the former — it has committed to 100 percent clean energy by 2045 and total, economy-wide carbon neutrality by 2045. And Gov. Gavin Newsom has also been trying to rally support for new funding from the state legislature to take on the threat of fire in a warming world.

But he and other California leaders still have a long way to go in helping communities play better defense against, and prepare long-term for, wildfire. “We are overloaded with assessments and short on actions,” said Ager.