The world certainly seems more flammable these days. Thousands of homes were lost last year in Sonoma County alone, and wildfires have raged across California all summer. And not just in California: Records from the federal National Interagency Fire Center show that U.S. acreage burned in wildfires leaped from 1.8 million in 1995 to 10 million in 2017.
But even as the burned acreage has jumped exponentially, the number of fires—or “ignitions” in wildfire-speak—dropped significantly, from 82,234 in 1995 to 71,499 in 2017. Why the discrepancy? Put simply, fires are getting harder to control, so they’re getting bigger. To blame are the build-up of forest fuels from decades of aggressive fire suppression as well as drier, hotter, and windier conditions caused in large part by climate change.
That’s only part of the problem, though. The fires are getting costlier, both in terms of human life and property loss. And a major—perhaps the major—driver to this trend is the “expanding bull’s eye” of high-risk development, specifically the rapid growth of Wildland-Urban Interface (WUI).
“Interface” is that transitional zone between suburbs or cities and forested areas. From a firefighter’s perspective, WUI combines the worst of both realms: Interface areas are not only cheek-to-jowl with fuel-rich forests, they’re also often characterized by dense housing tracts landscaped with lush, highly flammable vegetation. Today’s wildfires, in short, are not your grandpa’s wildfires; they’re usually hybrid, human-started fires, involving both structures and forests, which greatly complicates the task for wildfire fighters and escalates the cost in life and property.
A recent study shows that WUI, primarily from suburban and recreational development, is the fastest-growing land-use category in the lower 48 states. And home losses from wildfire correspond directly to the expansion of interface.
Anu Kramer, a postdoctoral research associate at the University of Wisconsin who took her PhD in environmental science, policy and management at Cal, co-authored the paper in the Proceedings of the National Academy of Sciences that examined WUI changes from 1990 to 2010.
“We found that there was a 33 percent increase in WUI for the period and a 41 percent increase in new homes built in WUI areas—from 30.8 million to 43.4 million,” Kramer said—meaning there are more and more zones where development abuts wildland. “Basically, this translates as greatly increased fire risk.”
Those statistics suggest that neither policy makers nor home owners have grasped the profound risks implied by building in pleasant, leafy—and highly combustible—environs, particularly in the West.
“The main takeaway from our most recent research is that these interface areas need to be targeted for outreach—education for home owners on creating defensible spaces, and regulations, and funding that would result in such things as fuel breaks, more sensible zoning, and mandates on fire resistant construction materials.”
Instead, there seems to be a kind of collective determination to repeat the mistakes of the past.
“I’m involved in some research on rebuilding trends after wildfires, looking at where new homes are going in,” said Kramer. “On average, 94 percent of buildings [in a burn zone] have been rebuilt after 25 years.”
Kramer and her colleagues created a computer model, which confirmed that post-fire construction tends to concentrate in areas of equal or higher fire risk than those that had last burned.
“Miranda Mockrin [a researcher with the U.S. Forest Service] has done a lot of work in Colorado on the social science aspects of wildfire,” Kramer said. “She looked at zoning changes after fires and found that yes, sometimes zoning gets stricter and people may be encouraged to build with materials that are more fire-safe, but in the majority of cases there were no changes, and in some instances restrictions were actually reduced. The potential for learning and adaptation after fires just isn’t being fulfilled.”
That dynamic seems in play in the North Bay, observed Kramer, where homes currently are being rebuilt in the exclusive Fountaingrove area. This enclave of expensive houses was located along a ridge on the margins of Santa Rosa. Just under a year ago on the evening of October 8th, the Tubbs Fire roared through the neighborhoods, consuming most of the homes and killing several people. The steep slopes and canyons of the ridge acted as chimneys, concentrating the full fury of the wind-driven flames onto the ridge top development.
It was a horrific event, but it was hardly an outlier. In fact, it had been predicted. In 1964, the Hanley Fire tracked virtually the same route as the Tubbs Fire, including the area now occupied by Fountaingrove. But in 1964, Fountaingrove didn’t exist, and the Hanley Fire destroyed relatively few structures. When construction on Fountaingrove started in the 1990s, many residents protested to Santa Rosa regulators, citing the Hanley blaze.
So why rebuild in high-risk areas? As Kramer explains, local governments are incentivized to rebuild as quickly as possible to recoup lost tax revenues and bring civic and economic life back to comfortable baselines. Unfortunately, environmental and geophysical changes—more frequent high wind events, longer and more frequent droughts, higher summertime temperatures and milder winters—mean that an increasing number of communities, even those outside of wildland interfaces, are considered high-risk for catastrophic wildfire.
The Tubbs Fire, for example, didn’t just burn Fountaingrove, a development with a significant WUI. It also flattened 1,200 homes in Coffey Park, an older middle-class development in a thoroughly suburban area located west of Highway 101 and far from anything that could be construed as a “wildland.” Extremely high winds drove masses of embers across 101, where they ignited structures and landscaping in Coffey Park and surrounding business complexes. Such winds were once considered anomalous by fire scientists. Not anymore. If ferocious wildfire-associated winds aren’t the new normal, they’re on their way. Winds reaching 143 mph destroyed scores of homes in the recent Carr Fire in Redding, during which a literal fire tornado killed two firefighters.
“[The Tubbs and Carr Fires] demonstrate how these strong winds can influence where a fire goes and what it does,” said Kramer. “They also show we need better models for predicting impacts and assessing risks. The models currently used by Cal Fire [California’s state wildfire fighting agency] have a pretty basic wind component that doesn’t account for the kind of high wind events we’ve begun seeing. So Max Mortiz [the head of the Mortiz Fire Regimes and Ecosystems Management Lab at Cal] is working with Cal Fire to bring their models up to date.”
The past few fire-ravaged years have made it clear that we have reached a tipping point. Epic wildfires are no longer rare, and they seem certain to gain in frequency and destructive power in coming decades. Moreover, the number of communities at dire risk is much higher than has been assumed. As Kramer’s work reveals, wildfire losses seem proportional to the growth of WUI. We can’t eliminate wildfire, but we can certainly reduce the impacts.
Paradoxically, that involves introducing more fire—controlled fire—into our wildlands to consume heavy fuel concentrations. It also entails moderating the dizzying expansion of WUI. Left unregulated, the trends in housing growth will simply perpetuate the destruction.