With flooding, we have rules about where to build and how to prevent calamity. Why not with fire?

The conventional wisdom in the wake of forest fires is that everyone rebuilds. Homeowners who live where nature and civilization rub up against each other go there for a reason – the views, the solitude, the independence. And when fire touches their property, that same allure leads them to rebuild. This is what fire professionals at the "wildland-urban interface" will generally tell you.

Whether most homeowners actually do this – and, more importantly, why – is a thornier question and an important one for land-use planners in an era of climate change. Since Hurricane Sandy last October, Americans have begun to talk more about the risks and responsibilities of building at the edge of water. But some similar, disquieting questions arise inland, in fire-prone places. Should we tell people not to – or how to – build there? Should people who've already built get to rebuild? What happens when private property owners need rescuing at public expense?

In at least one way, fire is different from flooding: One house becomes kindling for the next, and so your neighbor's building material matters, too, further complicating questions of regulation and collective risk. And as one land-use consultant recently told the New York Times, “There’s a self-selection factor in there — people who don’t want the government to do things tend to move to places where the government isn’t around to do things." Often, these are the places that are dry and vulnerable.

Below is a map of what researchers at the University of Wisconsin Spatial Analysis for Conservation and Sustainability Lab call the "wildland-urban interface":


That map shows, as of the 2010 Census, the interface where housing either abuts nature (picture a subdivision across the road from a forest preserve) or the intermix where houses are dotted amid nature on the outskirts of developed areas (like individually built homes in the woods). Most of the country is made up of vegetation, or farmland, or developed areas. But the red and yellow patches above show where the first and last groups encounter each other. And a third of all homes in the U.S. are within this zone. Most of the WUI in the humid East isn't prone to fire, but many of those patches in the West are.

To assess what's going on with housing development there, Patricia Alexandre, a Ph.D. candidate at the University of Wisconsin, has been pouring over historical Google Earth images within the boundaries of known fires in search of homes and who rebuilt. Her ongoing research has looked at 2,318 fires that caused structural damage in the continental U.S. between 2000 and 2005, an era that corresponds with the housing boom (and the best available early Google imagery). The largest number of damaged homes were in California:

Courtsey Patricia Alexander. Data collected on Google Earth based on the National Monitoring Trends of Burn Severity Burned Boundaries Dataset.

Of those properties, in that five-year time span, Alexandre found that 70 percent of homeowners rebuilt.

But while she was hunting through satellite imagery for destroyed and rebuilt homes, Alexandre came across another class of development that wasn't initially part of her research.

"I started realizing as I was going back and forth on Google Earth with the images in time, I saw wait – there are new houses coming up," she says. "This is also interesting."

The recent memory of fire apparently did nothing to deter the pace of new housing during the boom years. Put another way, ecology had little to do with where we built. "The numbers were quite impressive as well," Alexandre says. "There’s more new development than rebuilding. Of course this raises a lot of other questions that I don’t have the ability to answer, like the why. Why are people going to burned areas?"

Why do local communities enable them to?

In her dataset, the rates of development within these fire perimeters aren’t statistically much different from the development rates in each local county. But that’s surprising, too. We’d expect them to be much lower.

This suggests that we think about fire very differently from how we think about flooding. "With flooding," Alexandre says, "we do have lots of maps, we know where the flood plains are, there are rules. So why not with fire?"

Of course, in some communities there are rules. After the Waldo Canyon fire, which destroyed 347 homes in Colorado Springs last summer, the city passed new fire codes banning wooden siding and decks and requiring fire-resistant materials in construction. But the changes only apply to new and rebuilt homes, meaning that a 2013 stucco house may still have a 1980 tinderbox as its neighbor. And in places like Western Montana, as the New York Times noted, there's been considerably less appetite for new regulation.

Why, though, wouldn't these homeowners fear that their rebuilt homes would simply burn down again? Catastrophic forest fires are now a regular feature of the summer. And because of the way embers leap from roof to roof, a forest fire can quickly transform into an urban fire, a beast of a different nature (requiring different fire-fighting techniques) that can consume dense neighborhoods that appear on a map to be nowhere near the forest.

"There's research in the hazard literature suggesting that sometimes people who have gone through a hazardous event experience what's been termed as 'the gambler's fallacy,'" says Miranda Mockrin, a research scientist with the U.S. Forest Service Rocky Mountain Research Station who has studied the response of some Colorado communities to forest fires. "They see their personal odds of experiencing another hazard as low. It's sort of like, 'what are the odds that my house would burn down again? Or what are the odds that we have another Hurricane Sandy?'"

That fallacy is another argument in favor of smart land-use policies and building codes. If we as individuals aren't always in position to make the most rational risk assessments about where and how to build (a decision that could potentially impact fire-fighting resources and other people), does that elevate the community's duty to create some protections? As scientists, Mockrin and Alexndre shy away from the question of whether these people should be building, or rebuilding. But while we're already talking about flood risk, it is perhaps time for the rest of us to talk some more about fire risk, too.

Top image of a burned home in Yarnell, Arizona, photographed earlier this month: Todd Tamcsin/Reuters

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