Clearing the Wildfire Haze: Protecting Homes, Ecology, and Firefighters

Climate change is whipping up stronger wildfires, but conventional wisdom on how to protect homes — clearing brush — is actually making things worse. Recent science shows that homes themselves are fuel, highlighting the importance of making buildings more fire resistant. A growing movement to craft more resilient communities that can weather fires could reduce harm to firefighters, preserve habitat, and save taxpayers billions of dollars.



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After 19 elite firefighters died fighting a wildfire near Yarnell, Ariz., last summer, people upset by the tragedy questioned whether wildland firefighters should be risking their lives to save homes. They called for more responsibility from homeowners who put themselves in harm’s way by moving close to wilderness, demanding that they maintain their property in a manner that makes communities more resilient to fire or accept the consequences.

Some of the outraged, unfortunately, were pushing “solutions” based on misconceptions. How fire actually behaves is still widely misunderstood by homeowners, city and state agencies, and even some fire agencies. As a result, strategies employed to date have often destroyed native habitat without reducing fire risks. Sometimes they create more danger. What is needed, say experts, is more focus on fireproofing houses.

It is a problem that touches a surprising number of Americans. Living in what geographers call the wildland-urban interface (WUI) is not simply a lifestyle choice for the rich. In 2000, more than a third of U.S. residences were located in the WUI, housing 104 million people. In the West and Southeast, more than 45 percent of housing units are in the WUI. The two classic examples of development in the WUI — small towns in rural areas and suburbs close to large undeveloped areas — describe wide swaths of populous cities like San Diego and Los Angeles, and smaller towns like Boulder, Colo. and Flagstaff, Ariz.



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And what happens in the WUI is an issue of concern even for those of us comfortably ensconced in cities. That’s because we all pay for these recurring emergencies via our federal and state tax dollars, and that bill is rising.

The U.S. Forest Service and the Department of the Interior spent an average of $3.4 billion annually to fight fires in recent years, three times what they spent annually in the 1990s, according to the Congressional Research Service. And Federal Emergency Management Agency grants for fire management averaged $71.2 million annually between 2002 and 2011, more than three times the level of assistance the agency offered in the 1990s, according to a recent analysis by Headwaters Economics, a nonprofit research group that studies development in the West.

State spending on firefighting has also more than doubled in the past 10 years to more than $1.6 billion annually, according to the National Association of State Foresters.

Hotter Living

Curbing further population growth in the WUI will help keep the collision between fire and modern society from growing. But changing population and housing patterns requires thoughtful land-use planning, political will, and time.

Near term, minimizing fire risks and costs demands learning how to protect the homes that are already in the WUI. Science suggests that the conventional wisdom on protecting homes by clearing away all vegetation around them can in fact make buildings more vulnerable to burning. That’s because large fires generate high winds that, with plants removed, can barrel straight toward a house, carrying sparks with them.

“Total clearance creates a perfect bowling alley for embers,” said Richard Halsey, director of the California Chaparral Institute, a nonprofit educational organization.

On the other hand, vegetation can impede wind, and some species, such as California’s native oaks and Colorado’s aspens, can actually act as ember catchers or heat sinks, protecting a house from burning.

Carefully managing plants near the home is still an important part of fire protection — as long as the right plants are used in the right way — and as long as equal attention is paid to equipping houses with fire-resistant materials.

Without smarter efforts to reduce homes’ vulnerability to wildfire, home losses are likely to continue apace, along with firefighting costs, because prevalence and severity of wildfires are on the rise. “There is no more fire season. We have wildfires all year round,” said then-Gov. Arnold Schwarzenegger in the summer of 2008, when more than 2,700 fires were burning across California.

Wildfire “season” is lengthening across the United States and around the world. Climate change is a key driver. Increasing temperatures and drought, like the historic one California is currently limping through, dry out forests and shrublands. Warmer weather also empowers pests like the bark beetle, which can kill trees and make them more likely to burn hot when ignited.

Historically, fire was a natural part of our landscapes, touched off by lightning. Native Americans also ignited small burns regularly to manage edible plants and create hunting habitat. Fire should play a fundamental ecological role in 94 percent of wildland areas across the United States, according to a 2012 Forest Service report, from ponderosa pine forests in the Northwest and Rocky Mountain West, to the Southwest’s chaparral, to the Midwest’s tall grass prairies, to the pine barrens of New Jersey, to the South’s longleaf pine forests.

Over the past century, however, human influences have changed historic fire regimes in ways that raise risk. We inhibit fires because we fear for our parks and communities, while simultaneously setting accidental fires with cigarettes, campfire embers, or sparks from vehicles and equipment. These human activities are now the biggest factor in ignition risk.

The result is an increasing collision between fire and modern society. Over the long haul cities and counties can ease that tension by keeping new sprawl out of the WUI. A 2012 report from the California EPA found that property damage from wildfires could be 35 percent lower at century’s end if smart growth policies were adopted compared with just more business as usual.

Defensible Space

Today, however, a lot of misdirected energy is focused on “defensible space,” which is an extension of the firebreak concept. It has been the clarion call of home fire protection in the WUI since the latter decades of the 20th century. Agencies that set standards for defensible space commonly demand that vegetation be minimized within a 30-foot radius around houses and thinned out to 100 feet. The goal is to prevent burning vegetation from passing their flames to a structure.

In many jurisdictions such as California and Oregon, defensible space is a legal mandate in the WUI statewide. Arizona, Colorado, and New Mexico empower local governments to impose defensible space provisions on property owners.

However, defensible space is a concept that has been often misinterpreted and, as recent science suggests, oversold. The result is unnecessary ecological destruction, missed opportunities to reduce risks, and even increased risks.

Risks increase when homeowners misunderstand defensible space to mean a landscape devoid of all vegetation. California’s law, which went into effect in 2005, uses the terms “clearance” and “firebreak,” when in fact its provisions do not require removal of vegetation down to the soil.

“People hear the word ‘clearance’ and they clear everything,” said Halsey.

Clearing disturbs soil, making it ripe for weeds and the nonnative grasses that dominate California and large swaths of the west.


“Grasses are where most fires ignite,” said Jon Keeley, a research ecologist with the U.S. Geological Survey who specializes in the ecological impacts of wildfire.



A wildfire fueled by invasive cheatgrass burns fragile sage steppe habitat. Photo by USDA/NRCS.


In reality, creating effective defensible space is a far more nuanced process than clearing all vegetation, said Keeley, who is currently writing a review paper that will clarify what type of vegetation management is justified by science.

“Even though the law is written in terms of clearance, that’s not what you need. You need fuel reduction,” he said. That means removing dead material and selectively thinning vegetation.

Considering vertical and horizontal space is key. Pruning and selectively removing vegetation to provide space between shrubs, for example, creates gaps that prevent fire from spreading. Pruning low tree branches up to 6 or 8 feet, and pulling adjacent shrubs removes “fire ladders,” that can carry flames to higher tree branches.

Post-fire, clearing can cause erosion. Deep-rooted native shrubs hold onto soil on steep slopes, said Keeley. Whereas the nonnative grasses and herbaceous flowering plants that move in when soil is disturbed have shallow roots. That’s part of what “changes the fire season from six months in shrublands to 12 months in annual grasslands,” he said.

Some insurance companies have encouraged clearing. In states that map “red zones” that identify areas at high risk of wildfires, some insurance companies require that homeowners remove all vegetation within 100 feet of their property.

Sometimes property owners’ vegetation is removed without their permission, said Halsey. In rural parts of San Diego County, fire protection has been outsourced to private contractors. Residents have complained that the contractors deliver notices, giving people 30 days to object before the contractors clear their properties. The contractors often return to clear the land when people aren’t home and leave a bill for several thousands of dollars, Halsey said, who has helped some people in this situation navigate the legal system. One resident ultimately lost his property while attempting to fight the charges.

In other places, enforcement is uneven. Halsey said he has seen fire inspectors overlook Mexican fan palms – notorious for dangling dead material – planted against a house. When Halsey questioned the oversight, “Fire chiefs say, ‘We’ll never tell people to take out their fan palms because phones will start ringing at city council. It’s politically untenable,’” he said.

Beleaguered Native Plants

More divisive among experts is the question of plant choices. Some government and fire agencies recommend certain plants to favor or avoid, but Halsey said this is “mostly seat-of-the-pants opinion, not based on science.” Different agencies offer conflicting advice.

The idea that native plants are particularly flammable is a bias perpetuated through some fire agency recommendations and state laws. This is true especially in Southern California, where much native habitat is chaparral. And the language in California’s law on defensible space is pejorative to native plants, indicating that fires start with them.

Sabrina Drill, a natural resources adviser for the University of California Cooperative Extension who teaches about sustainable and fire-safe landscapes, views the attack on native plants as a myth that grew out of a perverse oversimplification of natural cycles. To whit: “Southern California burns, and this is natural. Hence all the things that are natural to this landscape burn.”

A wildlife conservation ecologist, Drill became interested in fire-safe landscapes through her work to restrain invasive plants. “In some cases, fire agencies were telling homeowners to prepare their property to withstand wildfire by using ice plant and ivy, which are invasive species,” she said. Some invasives popular in landscaping, such as pampas grass, are also a disaster from a fire perspective, she added.

In truth, individual species vary in their flammability, and that goes for both natives and nonnatives. Halsey agreed. The key is to trim dead material and irrigate one’s plants, Halsey said, and on the latter issue, natives offer a significant advantage. “It takes less water to hydrate them,” he said.

And there is more to living than fire protection. Sparing as much native vegetation as possible can help conserve the beauty and function of the natural landscape that attracted homeowners to the WUI in the first place. Clearing to bare earth isolates habitat into islands in a sea of development, said Drill, whereas a yard with native plants can provide a link between one natural area and another.

Hardening Homes

While careful landscaping and maintenance of native or water-retaining plants is one piece of reducing a home’s vulnerability to burning, fire science points to the home itself as the best target for fire prevention.

“We overemphasize plant treatment,” said Jack Cohen, a physicist for the U.S. Forest Service who studies fire behavior. People need to spend more time and money tightening up their homes to resist fire.

This focus has been missing because people misunderstand how wildfires behave, Cohen said. They incorrectly assume that high-intensity fires burn from wildlands directly into houses. Rather, 75 to 80 percent of the time, homes are burned to the ground by “firebrands,” flying embers that can travel a mile or more on the high winds that big fire create.

“The problem of houses burning down during wildfires is a home-ignition problem, not a wildfire control problem,” he said.

Firebrands can ignite wood piles and dead plants, but just as often they find ready fuel right on a house — in shingle roofs, on wooden decks or house-abutting fences, in dead plant litter caught in gutters and eaves, or attic mementos exposed by an open window. Cohen calls this universe of vulnerabilities the home ignition zone, or HIZ.

Ember-ignited house fires are well documented in recent studies, including investigations into the 2007 Witch Creek Fire in San Diego County; the 2007 Grass Valley Fire near Lake Arrowhead, Calif.; and the 2010 Fourmile Canyon Fire north of Boulder, Colo.

Based on such evidence, Halsey and others convinced the California State Legislature to amend the state’s defensible space rules as of 2009, relaxing the 100-foot requirements for houses that are relatively fire safe. “It was an important recognition: it’s the house that’s the fuel,” said Halsey.

Still, it can be hard for both homeowners and firefighters to accept. If a home burned because of one little ember, why wasn’t the fire caught and extinguished? The answer is that there simply aren’t enough firefighters to be watching every home, given the number and size of wildfires. “It’s not that they’re not there,” said Cohen. “It’s that they can’t be everywhere.”

Cohen visited South Lake Tahoe after the 2007 Angora Fire and attended a resident meeting where one angry homeowner stood up to say that if everybody had listened to her and cut the trees down, the disaster wouldn’t have occurred. “The irony is, that’s primarily what was left after fire,” he said. “Out of 240 houses destroyed, almost all had unconsumed vegetation around them.”

Many were native plants, such as conifers, that are fire resistant. “They’re there because they’re adapted to pass fires,” Cohen said.


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The arrow points to one of the only houses left standing after the 2003 Cedar Fire hit the San Diego community of Scripps Ranch. The owner had just replaced his wood shake roof with a firesafe composite material. Photo by Richard Halsey.


Homeowners can increase the likelihood that their homes will survive by improving their HIZs’ resistance to firebrands. Strategies include replacing wooden roof shingles with metal or tile, using nonflammable decking material, installing metal flashing in building seams, storing firewood away from the house, and keeping the building surface free from plant litter.

Some programs are beginning to recognize the value of shoring up structures. FEMA grants can now cover a portion of costs to reroof homes with fire-safe materials and to install ember-blocking attic vents. And in 2008, California adopted new building codes that require fire-resistant materials on new homes built in the WUI, said Daniel Berlant, information officer for Cal Fire (formerly the California Department of Forestry and Fire Protection).

Community Approaches

If the growing understanding of fire risk in the WUI makes homes more self-protective, the implications will be significant. Cohen emphasized that fire agencies could gain more freedom to allow wildfires to provide ecological benefit to the landscape — a process that is now greatly hindered by vulnerable residential development. But that freedom will require a broad adoption of home-protection measures, which the Forest Service is promoting nationally through its Fire-Adapted Communities program.

The Forest Service program is part of a fire-adapted community movement that’s growing nationally. “It’s the idea that a community can safely coexist with fire,” said Molly Mowery, founder of the Colorado-based consultancy Wildfire Planning International. The multifaceted approach gives everyone a role: homeowners, business owners, land managers, emergency responders, government and community officials. Wildfires near communities don’t have to be a major disaster if people adapt their habits and expectations to the point where they don’t really need outside assistance. Hardening a home and maintaining a yard are important steps, but those efforts can be hamstrung if your neighbors don’t do their part. As Mowery put it: “Neighbors are in your HIZ. The more buy-in there is, the more risk will be reduced.”

When Mowery consults on a property, her advice to clients is nuanced. For example, it could be OK to retain a small clump of trees as long as they’re separated from other vegetation, and aspen trees are a good heat shield, so they can stand closer to a house than other species.

“If there’s an older ponderosa pine — 50 years old, thick bark, healthy — you might want to keep that high-value tree, as long as its not too close to the structure,” she said. She also takes into consideration features like slope and prevailing winds.

One of her clients is Boulder County, Colo., which recently secured almost $1 million in seed money from the state to start its Wildfire Partners program which provides residents with subsidized home assessments and rebates for suggested fire-adaptive upgrades.

Wildfire Planning International also helps draft recommendations to improve land development codes, facilitates community organization, and helps individual and communities identify grants and funding for mitigation.

But some residents aren’t waiting for incentives. Mowery cited a group created in nearby Jefferson County, Colo. called Saws and Slaws, for chainsaws and coleslaws, which she compared to “an Amish barn-raising.” People band together to help make a property and home more fire safe, then share a potluck. It’s a sign, Mowery said, that “people are recognizing more that we are in this together.”