In 1991, when the city of Boulder asked Larry Donner to become its fire chief, he couldn’t believe his luck. A Denver native, Donner was forty-two and working as the fire chief of Iowa City. He and his wife, Susan Loo, missed the natural beauty of the Rocky Mountains: rolling meadows, colorful wildflowers, dense forests, rushing creeks. They also missed the outdoor adventures and the community that came with them.The kinds of outdoor adventures that Donner would contend with as fire chief, though, were stressful and dangerous—wildfires, damaging winds, flash floods—and Loo insisted that they find a home in a relatively safe area. “I didn’t want Larry worrying about his own house when there was an emergency,” she told me in September as the two of them sat at their dining-room table in bluejeans and T-shirts, casual as weekday hikers. They settled in Louisville, a pleasant suburb about nine miles southeast of Boulder, surrounded by open grasslands. “We’re miles from the foothills where the forest fires happen,” explained Donner, now seventy-seven and retired, with thin gray hair, glasses, and skin marbled by the fierce Colorado sun. “I figured it was safe.”Over the years, Donner worked hard to make his house fire-resistant. “I put in James Hardie board siding”—made of a noncombustible fibre-cement composite—“and a Class A fire-rated roof. I took a wood deck off the back, cleared out vegetation, and built a flagstone area next to the house. We had two giant spruce trees on the property that I just couldn’t cut down, but otherwise I thought I’d done everything.” In Boulder, he led a campaign in 1994 to ban wood shingles on new construction. “When you get a fire, they burn,” he said, “and in high winds they’re like Frisbees, flying torches.”For thirty years, as Boulder endured major fires and floods, Donner’s home remained untouched. But, in 2021, the weather turned. The grasses grew four or five feet during a wet spring, and, after a dry fall, the result was “like a field of matchsticks, chest high,” Donner said. The meadows that historically buffered his home, protecting it from wildfires, had now turned into fuel.On December 30th, a powerful windstorm swept down the Front Range foothills, with sustained winds in excess of forty-five miles an hour and gusts of up to a hundred. They rekindled a controlled debris fire on property occupied by Twelve Tribes, a fundamentalist Christian sect. Another fire was ignited by arcing power lines near the Marshall Mesa trailhead. At 11:05 A.M., the Boulder County Sheriff’s Office dispatched firefighters to a conflagration spreading across dry grassland, fuelled by every shingle and shed in its path. The Marshall Fire, as it became known, rapidly consumed structures, advancing east at what Donner described as “the speed of wind.”At 11:47 A.M., authorities issued the first evacuation orders, expanding them continuously as hurricane-force winds projected airborne embers ahead of a roughly half-mile front across wide streets and even across a multi-lane highway near Donner’s development. “Once you get an urban conflagration, there’s really nothing you can do to stop it,” Donner told me. “Now the fuel isn’t just grassland. It’s every house that catches fire, sending heat and flames and flying embers to the houses next to them. No water system is designed to handle an urban conflagration. It just collapses, and all you can do is pray.”Donner and Loo say they saw the fire approach their neighborhood long before they received an evacuation order. They grabbed a few cherished items and drove to a relative’s home, where they turned on the TV. “I could see our house burning behind the reporter,” Donner recounted. “I’d been worried about the spruce trees catching, but they were fine. The problem was I hadn’t put ember shields on our vents. I needed about one-eighth-inch wire mesh to cover attic vents, which I could have gotten at Home Depot.” Without that, embers got into the attic. “Our house burned top down, then inside out.”By the time the winds died, the Marshall Fire had destroyed more than a thousand structures and shattered communities. Donner and Loo lost nearly everything. Luckier neighbors, including a woman named Peggy Driscoll, returned to standing homes, but they were so saturated with smoke and soot that disaster-mitigation companies, after peeling them like onions for months, deemed them uninhabitable.Susan Loo and Larry Donner, on their porch in Louisville, Colorado. They rebuilt their home on the same spot as their previous one, which burned down in the Marshall Fire.“Look around,” Driscoll told me at her rebuilt mountain-modern-style house in unincorporated Boulder County. “It’s the suburbs. I’d always thought of wildfires as forest fires, and, since we’re not the typical landscape that burns, I didn’t think we were at risk.”The Marshall Fire showed that the danger of wildfires is broader and more serious than most people realize. Once wildfires reach dense residential areas, their spread resembles that of infectious diseases: no household can be fully protected unless surrounding properties are protected, too.“If you want your home to survive, you need to have herd immunity,” Jennifer Balch, a fire ecologist at the University of Colorado, Boulder, told me as we walked through her neighborhood, steps from a stunning mountain trail that’s rich with fire fuels in the fall. Dressed in the form-fitting athleisure endemic to the city, Balch explained that her community sits in the wildland-urban interface, or wui (pronounced “woo-ee”), where fire risk is highest. “I do get nervous when it’s hot, dry, and windy,” she said, brushing her curly blond hair from her eyes. “As you can see, we’re pretty far from herd immunity here.”For much of the past century, urban conflagrations seemed, like polio or measles, a scourge that science and government had conquered. Modernized fire departments, safer building materials, hydrants, and building codes had largely eliminated catastrophes like the Great Chicago Fire of 1871. But, by the nineteen-nineties, housing developments were spreading into forests and grasslands increasingly parched by climate change, bringing structure-to-structure fires back. The 2018 Camp Fire, in Paradise, California; the 2023 Lahaina Fire, on Maui; and the 2025 Palisades and Eaton Fires were devastating examples. Communities abroad face similar dangers, from Australia’s bushfire-prone suburbs to parts of Europe, Asia, and South America.Some residents whose homes were engulfed by fire understood that they lived on a combustible landscape; others were surprised. Balch, the ecologist, spent a decade building a data set that combined satellite information about the speed and spread of more than sixty thousand American wildfires from 2001 to 2020 with daily incident-command reports from fire-suppression teams, and two hundred million housing and property records. “The trends are remarkable,” she told me as we walked through the foothills near her neighborhood, grass crunching beneath our feet. “Here’s the main thing: Forget megafires. It’s fast fires that do the most damage.” Balch and her colleagues reported in Science that, among the conflagrations in their database, fast fires—those growing by more than sixteen hundred and twenty hectares on any single day—made up less than three per cent of the total but accounted for almost ninety per cent of the structures damaged or destroyed.Another Science paper, by a team led by Volker Radeloff, an ecologist at the University of Wisconsin, Madison, reports that from 1990 to 2020 the number of American homes in the wui increased by forty-six per cent, from thirty million to forty-four million. Although most U.S. regions are vulnerable to destructive conflagrations, Balch’s data show that such fires are becoming more prevalent—and much faster—in the West, where the average maximum daily growth of wildfire area increased by two hundred and fifty per cent between 2001 and 2020. “In California, it’s four hundred per cent,” she told me. “If you have a house there, that’s a terrifying fact.”Among the first institutions to recognize this change was the insurance industry, on which the modern housing market rests. By the nineteenth century, American mortgage lenders commonly required borrowers to carry fire insurance. During the New Deal, the federal government began insuring mortgage lenders against losses when borrowers defaulted, adding a second layer of protection. Together, these arrangements became foundational to American homeownership.In the twenty-first century, extreme weather has cracked that foundation. A hotter and more violent climate, combined with runaway development in high-risk areas, has helped make billion-dollar disasters more common. Soaring claims have been accompanied by soaring premiums. Meanwhile, insurers have increasingly exercised their option not to renew existing policies. For growing numbers of Americans, the insurance required for a mortgage is prohibitively expensive. In high-risk areas, it may be available only through state-run residual markets, including Fair Access to Insurance Requirements (FAIR) plans, which often come with high prices and limited benefits.Insurers have long sought to reduce risk by rewarding safety measures such as smoke alarms and security cameras. More recently, actuaries, policymakers, and fire experts have explored ways to do the same on a community-wide scale. Among them is Nancy Watkins, a property-and-casualty-insurance actuary at the global consultancy Milliman, who has had struggles with her own homeowners’-insurance coverage, in California.“I loved that old policy,” she said wistfully, as if recalling a beloved pet. But her insurer pulled out of the state, and the one she turned to next decided not to renew about half its policies in the area, including hers. We sat in her yard in Orinda, over the hills from Oakland, amid oak, redwood, maple, and lemon trees, overlooking dry grassland. “The chief actuary of another company told me, ‘Orinda is my worst nightmare,’ because we have so many high-value homes in a small area with terrible access, twisty roads, lots of overgrown vegetation, and very little mitigation. It’s so beautiful, but when I drive through these hills, I often think, Wow, an insurer could lose a lot of money here.”Watkins, who is sixty-five, has a mild Southern drawl, purple-dyed hair, and an analytic mind that eventually forced her to confront the fire risk she had long downplayed in her personal life, despite her professional expertise. Her husband led their local “Firewise” group, part of a National Fire Protection Association program that helps residents and neighborhoods organize around wildfire resistance. “He had been telling me for years that we should clear five feet around our house,” she said. “But we’d spent a lot of money on landscaping, and I liked it. I didn’t want to make the change.” She and her husband had invested heavily in her “California dream home,” but now they needed a better option than the state’s FAIR plan. “That’s when we decided to do the mitigation makeover.”There are two main ways to protect a home from fire. The first, “hardening,” replaces vulnerable building components, such as single-pane windows and vinyl gutters, with fire-resistant alternatives, such as double-pane, double-tempered windows and metal gutters. The second, creating “defensible space,” clears combustible material from the perimeter, particularly “Zone Zero,” the five feet closest to the building. That can mean removing vegetation, mulch, wood decks, fencing. “We put gravel and a stone stairway next to the house, got rid of a bench, moved the planters, found a way to keep leaves from piling up in the back,” Watkins told me. “I was afraid we’d have to cut down trees, but we only had to limb them.”Her house, which still has wood shingles and an ipê deck, falls short of the highest fire-resistance standards. But it proved safe enough for a new policy from a “non-admitted carrier,” an insurer operating legally without a California license. She knew that many families wouldn’t be so lucky. Amy Bach, of the consumer group United Policyholders, calls the trend toward insurance with higher premiums and diminished coverage “shrinkflation.” Watkins said that rate-setting rules adopted in California in 1988 prevent insurers from pricing policies according to risk, contributing to their retreat from the state. Meanwhile, progressives calling for reform point out that homeowner insurers in the U.S. are hardly suffering: according to the credit-rating agency AM Best, they posted $16.5 billion in underwriting profits in 2025.Watkins’s struggle to find coverage left her determined to improve the system. She joined forces with colleagues, including a director of fire research at Cal Poly, in San Luis Obispo, and a former fire chief for Orinda and a neighboring town, modelling fires and looking for ways to protect entire neighborhoods and towns. Right now, homeowners who reduce their fire risk may see little benefit in their insurance rates, Watkins explained, because their exposure depends heavily on neighboring properties, and there has been no systematic way to measure community-wide mitigation.“We’ve found a solution to this problem,” she said. She and her colleagues propose assessing entire neighborhoods and making the data available to insurers, lenders, scientists, and residents. This project, “wui Data Commons,” would help insurers identify safer communities—and, eventually, charge them less.Watkins and her collaborators have published research and pressed insurers to take community-level protection into account when setting premiums. “The assessment isn’t as easy as looking at photos on Google Maps,” she told me. Inspectors would have to examine windows, vents, siding, and defensible space, then check again as vegetation regrows. Homeowners might also upload videos of their property from their phones.How much mitigation is enough? Perhaps the most rigorous home-level standards come from the Insurance Institute for Business & Home Safety (I.B.H.S.), an industry-funded nonprofit that tests building materials and designs. But those standards may be too costly for existing homeowners to meet, and insurers debate what should qualify a policy for a renewal or a discount. Setting a threshold for an entire community, Watkins said, is even harder.To see these standards in action, I travelled to an I.B.H.S. demonstration at a fire-rescue training center in Lakewood, Colorado. Two small houses with fences stood on a paved lot. One had fibre-cement siding, Class A roofing, ember-resistant vents, closed eaves, double-paned, double-tempered windows in metal frames, steel patio furniture, and a five-foot perimeter of pavers. The other had open eaves, vinyl gutters, wood siding, a mulch bed, and juniper and fir trees planted against its walls. A narrow garden stretched before both houses. Four industrial fans stood ready to simulate high winds.It was a cool, unseasonably cloudy summer morning. Two uniformed firefighters wearing thick white gloves approached the garden and shot flames at the vegetation with red drip torches. Ignition proved surprisingly difficult. After delivering months of drought to the Rocky Mountain region, Mother Nature had sent light rain to the fire show. Instead of an explosive conflagration, the audience—developers, officials, and others—watched a slow, damp burn.“This is going to take a little longer than we expected,” Roy Wright, the insurance institute’s fifty-two-year-old C.E.O., said as he oversaw the proceedings. He was in a blue quarter-zip sweater and a white collared shirt, his manner professorial. “But it’s actually going to be a better demonstration, because, instead of seeing everything burn down quickly, you’re going to watch the fire progress in stages, one element at a time.”The first thing to ignite around the conventional house was the juniper, whose dense needles and twigs are filled with volatile oils and resins. It’s a notorious fire hazard in Colorado, where developers and homeowners plant the shrubs in clusters as inexpensive sources of privacy and shade. Minutes later, when the firefighters sped up the fans, flames and flying embers caught the wooden fence and the open eaves along the roofline. Dark smoke swirled up from the vinyl gutters as, at ground level, the fir and the mulch bed burned like candles.“Now watch,” Wright said softly. “The fire is spreading vertically up the wood siding. It’s going to keep climbing, and, since it got in that eave, it’s about to get inside, under the roof. From there, it’s over. The whole thing is coming down.” Soon the house was a bonfire, its radiant heat boring into my skin.Wright and I retreated to the back of the viewing area. “We’ve all been looking at the fire, because it’s hard not to,” he said. “But the real action today was at the other house. Look at it.” The hardened structure appeared unchanged. “The steel fence didn’t ignite. The roof didn’t ignite. The patio furniture didn’t ignite. There’s not a single mark on the siding. The windows are intact. You can see the effectiveness of the five-foot zone, too. The mulch around the edge is burning, but it’s not going to get past the pavers. The fire isn’t getting close.”I left the demonstration with a deeper appreciation for how homeowners and developers can reduce catastrophic property loss. Still, I remembered Peggy Driscoll, who lost her intact house to smoke damage after the Marshall Fire, and wondered whether the structure that survived the conflagration staged at Lakewood would still be habitable.Steve Ruffner, an executive at KB Home, one of the nation’s largest residential-construction companies, had a similar thought after a 2024 I.B.H.S. fire demonstration in Anaheim, California. He and I.B.H.S.’s chief product officer, Alister Watt, came up with an idea: What if they built an entire community in a fire-prone area to the I.B.H.S. mitigation standards, hardening not just each property but everything on the development’s land?In late September, I travelled to the suburbs northeast of San Diego to see Ruffner and Watt’s vision realized: a community-mitigation project that persuaded insurers to offer good coverage in a fire-prone area at reasonable rates. Dixon Trail, a nearly completed residential development at the base of high, dry foothills, consists of sixty-four ranch-style houses, most priced at about a million dollars and ranging from roughly two thousand to three thousand square feet. KB Home bought the land in 2022 and was preparing to build when Ruffner saw that fire demonstration in Anaheim. Dixon Trail became the first U.S. community to meet the I.B.H.S. Wildfire Prepared Neighborhood Technical Standard.I parked at the sales center, housed in one of four remaining unsold homes, and Ruffner greeted me before I reached the entrance. A tall man in his sixties, he had a jocular air and wore a blue corporate polo, black sunglasses, and khaki pants. “Before you see the property,” he told me, “you need to know that we are standing in what’s called a high fire-severity zone, and this is a wind corridor.”The temperature was in the mid-eighties, and a gentle breeze gave little hint of the Santa Ana winds that heighten the danger during the colder months. “Now let’s get you inside. You look like you don’t get much sunshine. I don’t want to barbecue your skin.”The demo unit, a four-bedroom house on an oversized corner lot with dramatic foothill views and an indoor-outdoor feel, was cool and spacious. It had high ceilings, double-paned sliding glass doors opening to a patio, and all-electric climate control powered by solar panels and heat pumps. Ruffner led me to the back yard, where fire-resistant lawn furniture sat on pavers. Young hopbush trees, Texas privets, and crimson pygmy barberries lined the perimeter, helping shield a block wall and a metal post. When I’d learned about the project, I’d wondered whether the rock gardens, stucco walls, and heavy masonry might make the development feel like a fortress, eliminating vibrant green life along with fires. In fact, Dixon Trail felt, if not lush, appealingly comfortable and colorful. The aesthetic, more Palm Desert than Pacific Grove, suits the habitat.As we left to tour the development, Roy Wright, of I.B.H.S., joined us, smiling like a proud parent. “There’s something I need to show you,” he said, leading me toward five houses near the community’s center. They predated Dixon Trail by decades, and their verdant landscaping—tall, leafy banana and queen palms, birds-of-paradise, red-flowering bougainvillea, shrubs planted in mulch—offered plenty of fuel for a fire. We stopped near an adobe-block house, where Wright pointed to hedges beneath the windows. “I’m not concerned about the structure siding as the first point of ignition, but look at those hedges,” he said. “Now, remember that, on the day the fire comes, we’ll have high, hot winds. They’re going to dry out that vegetation and, when the embers hit those hedges, they’re going to be connective. As soon as things heat up, that window’s going to fall out, and when that window falls out, the fire goes in.”At the start of the project, the owners of those older houses had asked Ruffner how to harden them. “But when it came to removing plants and trees next to their houses,” he told me, “they weren’t too hip.” Wright added, “They’re obviously not at the standard we want to see here.” The good news, he added, is that the older homes sit inside the development, where the new houses and fire-resistant landscaping will help buffer them from fires.Even the new houses will require ongoing fire-safety maintenance. In high-risk zones, homeowners’ choices—metal or wooden patio furniture; the proximity of trees and hedges to the building—make a difference. “We have design guidelines and maintenance rules that buyers agree to in their contract,” Ruffner told me. “But we don’t have to manage it much, because of the peer pressure here. If someone sees something, the homeowners’ association gets to them first.”Financial incentives help, too. “There’s one very big reason residents are respecting the guidelines,” Ruffner explained. “When we did this project, we found insurers that were willing to write homeowners’ policies at a rate that’s simply unbeatable. Sixteen hundred dollars per year. For comparison, the guy in the house next to this development told me he’s paying nine thousand dollars. That’s worse coverage for more money. Buyers can’t believe it when we tell them the price of their policy. One woman hugged me in the sales office! She said, ‘I never thought we’d save so much!’ So, yeah, they could try to change the design guidelines, but, if they did, they’d be paying a very steep price.”Ruffner and Wright know that communities across California and the rest of the U.S. are desperate for home insurance at Dixon Trail prices. That’s unrealistic. “It’s nearly impossible to hit the highest standard of fire protection all the way through a legacy neighborhood, especially one in a wui,” Wright told me. “In a new development, it’s just a question of spending a few thousand dollars more on certain design elements, and we know they’re going to pay for themselves quickly, in insurance savings alone.” I asked about the cost of hardening an older home nearby to the same level. “You’re talking tens of thousands of dollars,” he replied. “If you have to replace the windows, enclose the eaves, and change out the other elements, you’re talking maybe a hundred thousand dollars.” Even after such an expensive project, a local homeowner might qualify only for a FAIR plan. Without similar measures from neighbors—and insurers’ use of the community-level mitigations that Nancy Watkins and her colleagues promote—a decent policy would remain hard to find.Still, some communities are working toward herd immunity, making enough homes safer that they meet insurers’ thresholds. In a wui in the Berkeley Hills, I met Michel Thouati, a sixty-five-year-old technology entrepreneur wearing a white polo, black pants, and a phone holster. His house stood two streets away from a park featuring rolling grasslands and giant redwood and eucalyptus trees. He bought the house in 1997 for its sweeping views of the Golden Gate Bridge, explaining that, “for Europeans, that bridge is the great symbol of freedom and the American West, and I couldn’t think of a more beautiful place to live.”Thouati grew up on a French military base in Algeria and holds an engineering doctorate from the University of California, Berkeley. He speaks rapidly and precisely. We talked in his living room as the Bay and the San Francisco skyline glimmered in the late-afternoon sun. Earthquakes had long been his chief worry as a homeowner. “When we bought this house, it was made of the cheapest goddam materials. But I’m a systematic person, and I put together a long-term plan. As we started to remodel, whenever we demolished something, we would build earthquake anchors and shear walls, and triple the nail schedule to make it more earthquake-resistant. When we had to get rid of our siding, which was combustible, we went to fire-resistant fibre cement. Then we put in a metal roof.”Thouati and his wife spent most of the twenty-tens in Wisconsin, and returned in 2019 to a hotter and drier Berkeley. “Lawns had turned to rock gardens,” he said. “The whole area was less lush.” Neighbors warned him about wildfires, but, he confessed, “at first, I was in denial. I loved my gardens. I’d planted so many trees and plants here.” Outside, he showed me a carefully tended evergreen dogwood and a weeping dwarf sequoia with a rough, curling trunk. A Japanese maple was hung with winged seeds. The trees stood several feet from the house, behind gray-and-white gravel and near a cluster of potted plants. More trees lined a metal fence behind them, where a rock river wound toward a stone fountain. “It was just too emotional, the thought of losing all of this.”As Thouati weighed mitigation costs, COVID-19 pushed wildfire down his list of worries. He helped organize a mutual-aid network of four hundred drivers, which delivered more than a hundred and seventy-five thousand meals in its busiest year. “We had enormous good will in the community, and a real system for working together,” he told me. As COVID receded, he saw how residents might help address another problem the city was struggling to manage: wildfire.Thouati became a force behind the neighborhood’s Firewise group, expanding its volunteer services beyond education and home assessments to hands-on help with clearing vegetation. “I know how daunting it is to take on home mitigation,” he told me. When I cited Roy Wright’s estimate of a hundred thousand dollars, Thouati laughed. “If you’re trying to comply with I.B.H.S. enhanced standards, which you might need to get insurance coverage, the cost for a house like mine can easily reach three hundred thousand dollars. It’s impossible, unless you have money and you do it in stages. Ours took thirty years! But you can reduce fire risk by eighty per cent with some simple and fairly inexpensive things—a few thousand dollars. In Berkeley, the city will give you mesh for ember shields and gutter screens, which are very expensive, for free.”Walking with me along his street, Thouati sized up each house’s fire precautions and its residents’ willingness to help. “This one is mostly compliant,” he said, as we passed a property with a dark-wood back deck. “I don’t love wood, but it’s dimensional lumber, which is hard to burn, and, look, he’s got eighty feet of new metal fencing. It’s totally fire-safe.” At a stucco ranch with a walker on the patio, he explained, “She’s eighty-eight. We cleared most of her land last spring. We’re trying to get her enrolled in the residential-assistance program for people over sixty-five. She’s ninety per cent compliant, and the city will pay for the rest.” Across the street, a small home sat within a jungle of vegetation. Thouati sighed. “This one, they’re not interested. They think every plant and tree is a gift from God.”At a demonstration burn organized by the Insurance Institute for Business & Home Safety, flames spread from landscaping to a house with wood siding and open eaves. A neighboring structure, built with noncombustible materials and surrounded by a five-foot perimeter of pavers, sustained no visible damage.The insurance-consumer advocate Amy Bach had told me about residents she calls Good Karens, who reduce their own fire risk and press their neighbors to do the same. I asked Thouati how he handled holdouts. “We train our volunteers to never do enforcement,” he said. “That’s for the Berkeley Fire Department. Be the friend. Be the educator. Be the helper. Sometimes it takes years. See the house here?” He pointed to a two-story home with a patchwork of gray and green in the front yard. “They never wanted to cut anything, but this May a contractor showed up and started clearing out vegetation. They’re nowhere near where we want to be, but it’s getting better, and it’s all because of gentle pressure.”Despite these efforts, Thouati recognized the limits of volunteer organizing. “The fire modellers say you need about eighty-five-per-cent compliance to reach something like herd immunity in a neighborhood,” he told me. “We’ve made huge progress here, but in most places, even where there’s money and leadership, it’s hard to get to twenty-five per cent. Doing it on a voluntary basis won’t work.” He wanted local and state policies that mandated strict fire-safety codes for private properties and that funded substantial mitigation on public land.This past January, Berkeley rolled out the EMBER ordinance, which is among the nation’s most ambitious local wildfire-control efforts. It requires a five-foot ember-resistant buffer around buildings and at least six feet of clearance between roofs and overhanging tree branches in the Grizzly Peak and Panoramic Hill Mitigation Areas. In August, California’s Board of Forestry and Fire Protection approved similar, but slightly looser, rules. They were quickly pulled back for review, but statewide requirements could still take effect soon.Protecting communities also means managing the land around them. On a hot morning in Boulder, I drove to the Fourmile Canyon Creek trailhead to meet Paul Dennison, a rangy, bearded thirty-nine-year-old in bluejeans, brown boots, and a black T-shirt, who oversees wildfire mitigation in the city’s foothills and parks. He told me that a road trip through the Rockies had drawn him to firefighting. He joined Colorado’s fire service at twenty-six. Three years ago, he traded active suppression for the safer, equally challenging work of keeping wildfires from becoming cataclysms.Dennison led me into a parched meadow. Dried grasses bordered houses in one direction and stretched for miles into the foothills and mountains in the other. “We manage a seventy-two-square-mile public-land system, a greenbelt, that surrounds residential Boulder,” he explained. “It’s all a fire-prone environment. Natural areas to the west, primarily. Agricultural lands to the east. Sixteen thousand homes fall within our three wildfire-ignition-risk zones, and the strong downslope winds we get, usually in the fall, can drive a fire pretty much everywhere.”Since the Marshall Fire, Boulder has developed a plan to reduce fire risk across its varied terrain. Dennison led me off the canyon trail, warning that my shoes were no match for the cactus I’d nearly stepped on. He pointed to the grasses around us: just an inch or two high, several feet shorter than those farther uphill. “Once or twice a year, we do what we call our urban cattle drive, and just walk the cows from one treatment area to another on the outside of residential Boulder, occasionally crossing major roads,” he explained. “This year, a lot of drivers seemed confused about what we were doing, but when we explained it they thought it was pretty cool.”Dennison wanted a healthy, fire-resistant landscape, but the cattle had eaten too much. “See these patches of bare ground here? We didn’t have much rain this year, and since the grass wasn’t high when the cattle arrived, now it’s grazed down to the nub. In the future, we want to hit a four- to eight-inch range in areas like this. It’s kind of a high-wire act.” Other agencies use goats to trim mountain shrubs, but he was wary of that approach. “In some of these projects, goats eat so aggressively that they kill the shrubs, which means you’re taking live vegetation that retains moisture, and turning it into sticks that carry fire. We’re considering goats to create little breaks to help us get in and remove fuels by hand. But we want to be careful with this ecosystem. It’s easy to do harm.”Near communities, the priorities shift. “The closer you get to the homes,” Dennison told me, “the more the balance swings toward risk reduction, and the more aggressive we will be.” Beside the neighborhood off the canyon trail, he showed me a thirty-foot strip of grass separating back-yard fences from the wildlands above. “Right here, this is where we do perimeter mowing. We have hand crews—often locals who have been homeless and need work that’s not too technical—using weed whips, so they can avoid the little rocks on this landscape, and take away the fuel. We do it because, if a wildfire were approaching this community, you’d have firefighters behind these homes to defend them, and this creates a thirty-foot space where they could work safely.” Dennison draws on housing-location data and fire research by scholars like Jennifer Balch to decide how far to extend the work. “In this area, we do mowing and grazing up to a hundred feet from the houses, because the trail creates an additional buffer. In other places, where there are no roads or trails to slow down a fire, we go as far as three hundred feet.”His pickup, a red Chevrolet Colorado, took us to South Boulder’s pine savanna, near Shanahan Ridge. He gestured to grasslands beside the road. “Another one of our projects is shoulder mowing along the evacuation routes,” he told me. “If a fast-moving wildfire approaches Boulder, we’re going to have thousands of evacuees driving out while hundreds of firefighters are driving in. We don’t want high-intensity fire impacting those roads, and we want to create safe space for firefighters to engage the fire away from the roadway whenever possible.”At the wui, he showed me where the city was working to keep fire out of the tree canopy. “The goal here is to keep these trees from torching, because that’s when you get the most ember generation, with long-range transport to all those houses,” he explained, pointing to a row of houses between us and some scattered cottonwoods and pines. “From that neighborhood, we’ve got a continuous dried-grass understory leading right to the tops of the trees, so we’re pruning the lower tree limbs and using grazing and other methods for the grasses. Both help eliminate the ladder fuels, and keep fire out of the crowns.” The nearby houses, with abundant vegetation beside wooden fences, showed how much work remained.Before leaving Shanahan Ridge, we rested beneath a ponderosa pine, grateful for the shade of its combustible crown. I asked whether Boulder would revive prescribed burning, a practice that is rooted in the region’s Indigenous cultures and that, fire scientists had told me, has been shown to reduce wildfire risk. “I’d like to,” he replied. “It’s the best way to reduce surface fuel loads in forests, and it can be helpful for grasslands, too. But recently we haven’t been able to do it much. This year, during burn season, the whole county was under fire restrictions.”The risks weighed on Dennison. “This is city-managed land,” he explained. “If we have a prescribed fire escape, we have all these vulnerable, dense residential neighborhoods. Also, this is America, and there have been high-profile cases when burn bosses were criminally charged for fires that did damage. That’s a lot of responsibility for one person to carry.”The most contentious part of community mitigation happens at the property line, where one person’s landscaping can imperil a neighbor’s home. Even among people rebuilding after the Marshall Fire, the question of how much they owed one another remained unsettled.Before leaving Colorado, I returned to Louisville to meet Tawnya Somauroo, a fifty-year-old patent attorney and mother of twins who lost her house in the fire. She has since made neighborhood mitigation a civic mission. Her rebuilt home sits close to others in a hilly cul-de-sac with dramatic views. It’s a minimalist modern farmhouse built to resist fire, with a steep gable, white board-and-batten siding, and large, asymmetrical windows. A long bed of colorful wildflowers runs beside metal fencing, separated from the house by a wide concrete patio and an irrigated lawn. “We did everything we could to prevent another fire here,” Somauroo, in a dark-brown button-down sweater, her expressive face framed by blond curls, told me. She pointed out ember shields on the vents and a rock-and-gravel garden that had replaced vegetation and mulch. “It cost a little bit, but, the way I saw it, we didn’t have a choice.”Somauroo’s husband has chronic health problems after getting COVID, and her daughters need treatment for developmental issues. Evacuating, losing nearly everything, and rebuilding while holding a demanding job had upended her life. “Everyone here has been traumatized,” she told me, her voice shaky. “I did therapy. We have teen-agers in the neighborhood who still get in bed with their parents at night. What got me through this is the community. When the fire came, we didn’t get an evacuation order in time. We dove into each other’s houses, smashed into doors, yelled, screamed, and got each other out. Then we stuck together through the recovery—which wasn’t easy, because we were scattered all over the area. But we started a Slack to share information about everything, like insurance adjusters and mortgage servicers. We did happy hours, where you could just drink a beer with other people who were in the same situation, and got it.”When her new house was ready, about two years after the fire, Somauroo couldn’t wait to return. “It wasn’t just the house,” she told me. “This is a cool neighborhood. We’ve got older people, young people, families with kids for my girls to play with—that’s what made it worth coming back.” At first, she was relieved to see neighbors rebuilding with similar precautions: Class A roofing, Hardie siding, five-foot perimeters free of mulch and vegetation. But, as more houses went up, some for new families, she felt that standards slipped. “We’d see inconsistencies, like metal fencing, which is good, but then lots of new juniper trees, which is like asking for fire,” she said. “Or a fire-mitigated house with wooden fence wings attached. It can feel like having someone walk into a restaurant and lighting a cigarette. They aren’t just putting themselves at risk, they’re putting you at risk, too.”In the past two years, Somauroo has become a Good Karen, helping secure a local Zone Zero ordinance and a juniper-tree ban, then pressing neighbors to comply. Not long ago, a family moved in across the cul-de-sac. One of their daughters quickly became best friends with her children, but Somauroo was alarmed when ten trees appeared in the newcomers’ yard, some of which she thought stood within the required five-foot buffer. She texted the parents to ask whether they were violating the ordinance. They took offense, then insisted that their landscaper had misplaced just one tree, which they had promptly moved. Somauroo was unconvinced.She knew that her safety still depended on her neighbors. Every new owner or freshly planted shrub could reopen the question of how much they owed one another. Standing in her driveway, she looked across the cul-de-sac at the new vegetation and the arid hills beyond. “I wouldn’t care if people were just going to burn their own house down,” she said, “but we’re at a pretty high level of conflagration danger. As climate-change survivors, we have a right to live in a safer neighborhood. We’re not going through that again.” ?