From downtown Los Angeles all the way out to the edge of the Line Fire is sprawl that turns into more sprawl. It’s just block after block after block of homes and businesses and people living their life, until on one side of the street is a suburban neighborhood, and on the other side, a 26,000-acre wildfire. Some 65,000 buildings are threatened, and more than 10,000 people have been ordered to evacuate.
In recent years, fires have begun spilling into places dominated by people. Americans who live on the edges of major cities have long been much safer from the threat of fire than those who live in the middle of a forest. But wildfires in the West are growing so big, and so quickly, that cities are becoming vulnerable too.
Cities used to burn all the time. My predecessors at The Atlantic covered urban blazes in Portland, Maine (1866), and in the magazine’s hometown of Boston (1872). Chicago famously burned in 1871. These began as urban fires, started by human error or other mishaps—legend blames the Great Chicago Fire on a cow knocking over a lantern in a barn—but natural disasters could set them off too: San Francisco went up in flames in 1906, in the aftermath of a devastating earthquake. In the 20th century, people started to get serious about fire prevention. They developed thorough fire codes, the kind we’re used to today: sprinkler systems, fire exits, evacuation signs. Catastrophic urban fires became old horror stories.
Then, in the 21st century, the wildfires got big—so big that they started roaring into more densely populated areas. In 2017, a fire hit Santa Rosa, in California’s wine country, and flattened more than 5,000 structures. Then, in 2018, a fire tornado tore into the fringes of Redding (population 91,000), in Northern California. In 2021, a late-December fire in Colorado blew into the Boulder suburbs, destroying about 1,000 homes. Then, last year, on Maui, the deadliest fire recorded in modern American history destroyed the town of Lahaina in a matter of hours.
“I see it as like watching polio come back, or some plague that we fixed,” Stephen J. Pyne, a professor emeritus at Arizona State University and the author of The Pyrocene, told me. Pyne was part of the team behind a 2023 paper arguing that, although public perception of these disasters is that they were “wildfires that involved houses,” they really were “urban fires initiated by wildfires.” Essentially, even if a fire starts as a wildfire, when it reaches an urban area, it can change so much in the way it spreads that it’s a different beast. A wildfire moves among trees, but an urban fire moves among buildings.
Modern communities aren’t built to prepare for this kind of spillover. “The problem is fundamentally that we have built cities and towns without all the pyric hygiene that used to come with the cities,” Pyne explained. For decades, no one had to think about this problem, so no one did, even as cities grew and sprawl became a default. “Everybody thought it was done,” he said.
When fire scientists talk about urban fire, they don’t necessarily mean a fire unfolding in the center of a major city. They also mean suburbs and smaller cities—anywhere that has homes close together. Fighting a fire deep in a forest requires a very different strategy than fighting a fire in a neighborhood. Wildland firefighters try to prioritize life and property, but their job is to wrangle blazes into control. That could mean letting some areas burn if they’re not densely inhabited. But for urban firefighters, as Pyne pointed out, “every fire is an existential threat to life and property.” When an urban spillover fire occurs, firefighters have to deal with both types of fire at once. It’s no wonder that these types of fires are among some of the costliest and most destructive in recent history.
Part of what’s causing so many of these spillover events are embers. Giant fires can emit sparks that, when blown by the wind, can travel up to five miles ahead of the fire. Pyne compared them to a blizzard, or a swarm of locusts. They can burrow through a rooftop vent into a home’s attic, igniting some forgotten box of old clothes. Then the whole house catches fire. The solution is, essentially, to fortify the homes on the outskirts of communities. Homes can be built with special, more fire-resistant materials, and homeowners can clear their property of highly flammable items close to their house. These are standard precautions, sometimes even required by law for people who live on the edges of forests. But now cities and homeowners have more reason to weigh taking these precautions miles into the built environment. Barring extreme wildfire conditions, a fire probably wouldn’t burn all the way to the skyscrapers of Los Angeles, but one could burn thousands of homes on the fringe of the city.
The Line Fire isn’t even the only fire burning around Los Angeles right now; it’s just the biggest. Thankfully, it appears to be moving north and east, away from the suburbs and deeper into the forest, and firefighters have been able to contain the part of the fire that brushes up against the most densely populated area, Rick Carhart, a public-information officer with Cal Fire, told me. (Some mountain towns, including Big Bear Lake, are still under threat.) The wind occasionally changes directions in a way that’s unpredictable—but unless they make a catastrophic shift, the L.A. suburbs seem safe.
Still, the whole thing is just a bit too close for comfort. Major fires are burning across the West right now, in Oregon and Nevada and Idaho and Montana. Some of those fires are bigger than the Line Fire; so much area is burning right now that the country’s firefighting resources are strained. Fires keep getting larger and unrulier, thanks in part to climate change—but also because, over the past century, Americans suppressed many natural fires rather than letting them burn through. Now the forests are loaded with potential fuel, and big fires keep happening.
These fires mean fighting that much harder to keep them in the wildland. Fires are a natural part of many forests’ ecology; it’s not unusual for forests to burn. But humans, perhaps a bit arrogantly, thought they had bumped the problem off their streets and back into the woods forever. Now it’s creeping back in, and flames keep brushing up against our communities, forcing us to rethink who is at risk.
