Villas reduced to ashes, flames escaping from the window of a church, a fast-food restaurant swept away by an incandescent downpour and palm trees consumed at the speed of a cigarette… Watching a city burn, for the historian of the late Stephen Pyne, quoted by the Los Angeles Times, “It’s like watching polio return.” Once eradicated by centuries of progress in construction, the threat of deadly and destructive urban fires is resurgent thanks to the expansion of cities in forest areas, coupled with extreme weather conditions favored by climate change.
Ten days after the start of the fires, the flames are still swallowing hundreds of hectares. In total, more than 12,300 homes and other buildings were destroyed or damaged, according to a provisional estimate as of Friday January 17. Behind these numbers, so many traumatized families that California Governor Gavin Newsom wants to help “recover faster and stronger. Starting from scratch, but how to rebuild without repeating the mistakes of the past?
“When the first house catches fire, it’s no longer a forest fire,” observes Rémi Savazzi, fire expert from the National Forestry Office (ONF). “There, we clearly observe that it is no longer the vegetation which serves as fuel, it is the house which, by burning, generates energy such that the fire spreads to another, then to another, then another , etc.“Fighting against fire requires the construction of homes that burn less,” he emphasizes, pointing out the vulnerabilities of wooden frame houses, common across the Atlantic. Inside a house, fire, formidable, gaining power, agrees Anne Ganteaume, forest fire specialist at the National Research Institute for Agriculture, Food and the Environment: “There is an extremely large combustible mass. Once the fire comes in, it’s over.”
At the border between the city and nature, the areas “habitat-forest interface” are naturally the most exposed to the risk of fire. Also, the challenge is not only to prevent forest fires from breaking out there, but also from spreading there.
The numerous luxurious villas in the Pacific Palisades district devoured by fire confirm this observation. “They are well built, but they often have large bay windows with a view of the ocean and no shutters”continues Anne Ganteaume. Under these conditions, “the windows break and the fire comes in. Put shutters, choose thicker glass so that the window resists heat radiation… These are somewhat obvious things.” She also cites Australia, where it is now compulsory in some places to equip new houses with aluminum beams.
In a California regularly plagued by megafires, construction in risk zones has only been regulated since 2008. If certain materials are imposed for the exteriors and roofs of new buildings, “the question always arises of those who were already there”, pointe Anne Ganteaume. Thus, most of the houses destroyed in 2018 in the Paradise firein northern California, had been built before these standards came into force.
However, old houses can also defend themselves, including from Los Angeles, a megalopolis enveloped in chaparral, a thicket of bushes typical of southern California. The golden rule? Censure the continuity of vegetation likely to blaze thanks to clearing. This practice obligatory in France around homes (up to 50 m, at least), as well as along access roads, is worth the best technologies, but often comes up against ignorance and sometimes negligence on the part of residents.
In a guide practical with the air of a manifestothe California Chaparral Institute thus believes that the public authorities have abandoned the lever of pedagogy. “It is possible to make homes almost completely fire resistant through renovations, outdoor sprinklers and community firefighting groups,” assures this NGO, created in 2003 after the dramatic Cedar Fire (15 deaths and 2,232 homes destroyed) in San Diego County.
In the middle of the devastated area, the Getty Villa, a museum located on a wooded hill, resisted the flames thanks to a rigorous fire protocol and mobilized staff, reports its executive director au Los Angeles Times. Likewise, in the city of Lahaina (Hawaii), destroyed in 2023 by fire, the “house with the red roof”, which has become emblematic, survived thanks to its freshly renovated metal roof and the cutting of vegetation directly in contact with the the building, its owners explained to the site Civil Beatbased in Honolulu. A one meter wide pebble border had been installed at the initiative of residents who feared at the time not fire, but termites.
“No pile of wood stored against the house, the beautiful cypress stuck to the facade, the hedge which touches the wall, the garden furniture, the dead leaves or the pine thorns stuck in the gutter or between the boards of the terrace” are all food for the fire, lists Rémi Savazzi. “We can never stress enough the importance of cleaning these elements,” insists the ONF expert, recalling that all it takes is a spark thrown by the wind to start another fire.
To Los Angeles, “Firefighters reported seeing these embers starting fires two or three kilometers ahead of the main front of the flames,” confirmed in The Atlantic Michael Gollner, specialist in the study of fire at the University of California, Berkeley. For him too, measures must be taken “so that these embers do not start new fires”, he continued, echoing the story of the manager of a Pacific Palisades apartment complex. The latter told AFP that he had avoided a disaster by dipping into the swimming pool to extinguish a nearby eucalyptus tree, hit by an ember.
Should we let people live in high fire risk areas like Malibu, already hit by the Franklin Fire in December (20 structures destroyed), just weeks before the current disaster, or the Wooley Fire, in 2018 (1,600 structures destroyed)? For Crystal A. Kolden, director of the UC Merced Fire Resilience Center at the University of California, the danger comes not so much from locating residences in an exposed region but from changing land use. in the broad sense.
“Until the 1960s, much of the Santa Monica Mountains were still worked by ranches,” recalls this former firefighter. Gold, “grazing animals consume fine fuels and reduce shrub growth”she continues in a message published on the social network Bluesky. Prized for their access to nature, these urban pockets developed jointly with the departure of farmers and their animals, who provided this buffer zone between the city and the chaparral.
The problem does not only concern the United States, points out Rémi Savazzi. “You just have to look at aerial images from fifty years ago, in the Mediterranean. We had a very different organization of the territory: a well-concentrated village core, well-kept fields around it and, further away, the forest, describes the ONF expert. The progression of urbanization in one direction and of forests in the other, at the rate of agricultural abandonment, has created plus d’interfaces”.
Faced with this change in the landscape, France relies on risk prevention plans established by the various State actors present in a given territory. “DIn areas with a high fire risk, building permits are refused.illustrates Anne Ganteaume, even if here too, “There are still homes that were built before these plans were put in place.”
At the end of June, a study from the University of California estimated that at least 1.5 million houses had been built in the forest-housing interface zone over the last thirty years, making this State the champion in terms of the number of inhabitants living in these areas, which are more often at risk. This boom is fueled by a deep real estate crisis that is hitting the middle and working classes, who are now forced to move away from city centers.
Faced with this housing shortage and to respond to the distress of the victims of Los Angeles, Gavin Newson signed a decree on January 12 allowing “reduce the time it takes to obtain permits [de construire]”. This text repeals, for fire victims, the rules of the California Environmental Quality Act, a pillar of local environmental policy. Because in cities hit by violent fires, reconstruction is slow and painful. In Lahaina, Hawaii, the residents of the “house with the red roof” have still not found their neighbors, sixteen months after the fire.
In Paradise, the municipality required that each new house meet state-of-the-art standards for fire protection systems. Six years after the tragedy, the San Francisco Chronicle returned to the site, to meet residents who were safe… and fewer in number: out of 11,000 homes destroyed in 2018, only 2,500 were rebuilt.
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