A typical single-family house is encircled by green, its shrubs and plants sitting just under windows and hugging exterior walls. It's an image that California is trying to get homeowners to rethink as the state's risk of extreme wildfires grows.
One year after the fast-moving Eaton and Palisades Fires destroyed more than 16,000 structures in Los Angeles, California is drafting the toughest statewide rules in the country for vegetation. In areas at risk of wildfires, homeowners would be required to clear some or all of the plants within five feet of their house, depending on what regulators decide. Well-maintained trees would still be allowed.
The idea, called Zone Zero, is to prevent plants and flammable items from igniting during a wildfire, spreading flames to the house and the surrounding neighborhood. In high winds, most homes burn down due to embers, the tiny bits of burning debris carried by the wind.
Still, the pushback has been strong, even in the Los Angeles area neighborhoods where so many lost homes. In public meetings, homeowners have voiced concerns about losing greenery and shade, as well as the cost of clearing the vegetation. Some say they believe plants and hedges saved their homes by acting as a buffer, though many scientific studies show that vegetation increases the risk a building will burn.
The new defensible space rules will affect about 17% of buildings in California. But they could set a much bigger precedent across the West, as more states deal with wildfires growing increasingly destructive as the climate gets hotter.
"How we step up and do this is hard, but I think we have to adapt and change a bit if we're going to try to not keep losing our homes," says Michael Gollner, who runs the Berkeley Fire Research Lab at UC Berkeley.
Hundreds of tiny fires
When the Eaton Fire broke out the evening of January 7th, Richard Snyder was at his home in Pasadena, working on a powerpoint presentation about wildfire risk. Snyder had spent more than 30 years in firefighting before retiring and now does wildfire risk consulting. So when he saw the smoke in the nearby foothills, driven by powerful winds, he knew it didn't look good.
"I know where the smoke is going is going to be where the fire is going and I saw this smoke heading off into Pasadena," Snyder says.
He told his wife to evacuate and started telling neighbors to be ready. Snyder decided to stay. Although the fire itself was still more than a mile away, he knew the biggest danger was the glowing embers being blown into his neighborhood by the wind.
"And then it happened," he recalls. "There was a palm tree that lit off and showered our neighborhood with embers and it started a fence on fire at my neighbor's house. Myself and two other retired firefighters tried to put that fire out with garden hoses and it wouldn't work. It was too hot and the wind was too strong."
In windy conditions, embers can rapidly spread a fire, landing in dry leaves in a roof gutter, bark mulch on the ground or even being sucked into an attic through a vent. Once that fire gets going, the extreme heat and embers help it spread to neighboring buildings.
"I'm looking over and I'm seeing my St. Augustine grass burning," Snyder says. "Who would have thought that green St. Augustine grass would start burning? There's hundreds of little tiny fires burning in the yards and next to the houses of my neighbors."
Several homes in Snyder's neighborhood were lost. His own survived, but with damage. While he says it was a shock, it wasn't surprising to him. For years, wildfire experts had been finding that houses are vulnerable to wildfires both because of the building materials they're constructed with and when something flammable is next to the house. The concept of Zone Zero focuses on the crucial zone within five feet of a structure.
"We're not going to stop the fires, but we can absolutely keep them from burning our houses down," Snyder says. "But it's a change."
Public meetings get heated
California regulators are creating rules for the "ember-resistant zone" next to houses under state law. The original deadline was 2023, but the effort flagged. After the Los Angeles fires, Governor Gavin Newsom set a new deadline for the end of 2025. With all the debate, regulators pushed past that deadline and say they expect to keep working through March to gather more feedback.
The proposed rules would prohibit flammable items such as firewood, bark mulch, dead leaves and weeds within five feet of a house. Fences and gates would need to be made of metal or other non-combustible materials in that zone. The rules wouldn't go into effect for existing homes for three years and local fire agencies would have some discretion over tailoring it for their areas.
The sticking point is over green vegetation. Trees would be allowed as long as they're well-maintained, by keeping branches five feet above the roofline, for example. When it comes to plants, regulators are considering several options: only allowing potted plants in Zone Zero, allowing plants under 18 inches, or allowing any well-maintained plants with no dead material.
The change isn't being welcomed by some California residents. In September, California's Board of Forestry & Fire Protection held a public hearing in Pasadena to gather feedback on the proposed rules.
"Our community just endured the most destructive residential fire disasters in modern history, yet this board is pushing Zone Zero policies that completely miss the mark," Jessica Rogers of the Pacific Palisades Resident Association said at the hearing. "My home and my neighbors' homes burned because of adjacent structures, not vegetation."
In the hours of public testimony, some residents spoke in support of clearing Zone Zero to prepare for wildfires that will inevitably come again. Other residents pushed back, worried that houses on small lots would lose too much greenery and shade, reducing wildlife habitat. Some raised concerns about the cost, since the new rules wouldn't include funding for landscaping work, though California is developing other programs for that. A few residents noted that in the aftermath of the fires, some plants were still left standing.
"I saw the well-hydrated hedges that I had planted protecting my house, acting as a fire catcher, essentially, because they were upwind," Pacific Palisades resident Martin Hak testified at the hearing.
"We know that not everyone will agree with every decision or aspect of what comes next," Board of Forestry & Fire Protection executive officer Tony Andersen wrote about the Zone Zero rules. "But we do know that many Californians agree that protecting our communities is not a passing fad or a momentary response." The board also posted its responses to many of the questions raised at the hearings.
Do green plants burn?
"We don't really know how often plants can be 'protective' and provide a buffer for homes," says Max Moritz, wildfire specialist with the University of California Cooperative Extension at UC Santa Barbara.
The destruction in a wildfire can be a patchwork, with some homes and plants left standing directly next to others burned to the ground. In the aftermath, it's difficult to know when vegetation was responsible for spreading fire because the evidence is often completely destroyed.
Moritz is one of the few fire experts who say that green plants may not pose a risk to houses and that more research needs to be done. Greener plants, which hold water in their leaves, are harder to ignite. He agrees that some plants, like highly flammable juniper and cypress, should not be allowed, nor should plants with dead leaves or dry branches.
"The really important aspect to the plants is the dead material," he says. "If most homeowners are just going to let dead material accumulate in Zone Zero anyway, then it makes sense that there shouldn't be any plants in Zone Zero."
Other wildfire experts warn that in the hot, windy conditions of an extreme wildfire, all vegetation poses a potential threat.
"Just because a plant is very moist doesn't mean it's non-flammable," says Gollner of UC Berkeley. "Having a well-watered plant is less of a risk, but it's not no risk."
What makes things burn
Gollner runs a "burn lab" on campus, where his team studies how and why materials burn. There, they place a well-watered shrub inside a special chamber lined with sensors. They ignite a small bit of mulch under the plant. After a few minutes, the flames creep up into the base of the plant.
"You can see, once the flames touch the leaves, they immediately dry out and burn," he says.
Gollner says in a wildfire, if a neighbor's fence or shed is on fire, it can dry out and ignite the vegetation next to a home. If those plants are within Zone Zero, the fire can then reach a neighboring house. Even shrubs and hedges that look healthy on the outside are often dry and bare in the interior. At a recent California Board of Forestry meeting, Gollner's colleagues presented their recent experiments about how green plants can burn.
Other scientific studies show that vegetation is influential in wildfire risk. A team from the Insurance Institute for Business & Home Safety, a non-profit research group funded by the insurance industry, inspected damage at more than 250 homes in the Los Angeles fires. They found when Zone Zero had vegetation in quarter or more of it, the chances that a home was damaged or destroyed were almost 90%.
Gollner and colleagues also looked at several of California's recent wildfires and used computer models to simulate those burns under different conditions. Their study found Zone Zero rules could have reduced structure losses by 17%. Another study looking at the 2018 Camp Fire and the 2017 Thomas Fire found having mostly vegetation within six feet of the walls was a big factor in whether the building was lost. Other studies have also shown the importance of defensible space.
Still, minimizing vegetation alone won't guarantee that homes survive. Wildfire experts say buildings need to be fire-resistant as well, a crucial factor in reducing fire risk. Many older homes have wood roofs, wood siding or single-paned windows, which are much more vulnerable to burning. Gutters need to be clear of dead leaves and attic vents need to be covered in a fine mesh, so embers don't get inside.
Homes built after 2007 in wildfire zones are required to meet California's building codes for fire-resistant materials, but most of the state's housing stock is older than that. Some vulnerabilities can't be changed, like when houses are built close together on smaller lots.
With wildfires, neighborhoods are only as strong as their weakest link. Once a fire starts, it can spread from house to house, so wildfire preparation is far more effective when an entire community fortifies itself – something regulators have cited as a reason for the new vegetation rules.
"It's a change of aesthetic, and it's incredibly difficult because it's people's private property," Gollner says. "But a wildland fire is unique amongst all catastrophes in that what your neighbor does directly affects you. We know that whatever we do, it's got to be across the community."
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