Thanks to a warming climate, the West has entered the era of the mega-wildfire: bigger, more dangerous, and maybe coming to a neighborhood near you

Peter Fish,  – August 6, 2007

Anyone who has seen the aftermath of a wildfire on television -or, more harrowingly, in person – knows its risks. The ghostlychimneys of vanished houses, the melted frames of automobiles inblackened driveways – these aren’t images you forget. This is whythe West tends to remember its fires with the fearful reverence inwhich soldiers recall great battles: Montana’s Mann Gulch, 1949.Oakland Hills, 1991. San Diego’s Cedar, 2003.

Yet even though wildfires have always come with the territory -they are, like earthquakes, part of the equation of living here – agrowing number of researchers believes that global warming is, inthe West, generating wildfires that are bigger and more dangerousthan ever before. And the fire threat is growing just as we’removing into wildland in ever greater numbers.

Fighting “the Smokey Bear effect”

A professor at the University of California’s new Merced campus,Anthony Westerling may have been genetically predisposed to studyfire. “My maternal grandfather was an L.A. County fireman,” hesays, “and before that, a forest ranger. My mother is fascinated byfire. When I was a kid, we spent every summer in the Sierra, andshe would pile us into a car and drive out to watch all the bigfires – at a safe distance, of course.”

All this was, perhaps, perfect preparation for Westerling’sinvestigation into the link between fires and climate. Over thelast decade, the West has experienced some of the largest fires indocumented history – “mega-fires,” ones that burn more than 100,000acres. Like this summer’s Milford Flat fire in Utah (the largest instate history), 2006’s Derby fire in Montana, the 2002 Biscuit fire(Oregon’s biggest in a century), and the 2002 Rodeo-Chediski fire(Arizona’s largest).

Just as bad, wildfire season seems to be starting earlier. ThisJune’s Angora fire, which destroyed 242 homes near Lake Tahoe’sCalifornia side, struck a month before the traditional season forbig fires in the Sierra Nevada. The question is: Are we gettingthese bigger, hotter, earlier, more frequent wildfires because ourclimate is getting warmer?

But arriving at an answer is complicated. You need to determinehow the West’s 2007 summer temperatures compare with temperaturesin the summer of 1957, and 1857, and 1457. You need to know how2007’s wildfires compare in size and intensity with the wildfiresof the past. Acquiring this data – from climate records, treerings, soil samples, pioneer journals – is not easy. And then youneed to understand how the two sets of data relate.

“I was skeptical about being able to see a link betweenincreased fires and warmer temperatures,” says Thomas Swetnam, oneof Westerling’s co-researchers. As director of the University ofArizona’s Laboratory of Tree-Ring Research, Swetnam has spent hisentire career studying the relationship between forests andclimate.

There is an additional complexity, Swetnam explains, and that’sus. Even ignoring our possible effects on climate, we’ve alreadyhad a big impact on fire in the West. We start wildfires, sometimesaccidentally – and sometimes on purpose.

But at the same time, over the last century we’ve spent vastamounts of manpower and money to prevent and suppress wildfires,interrupting natural fire cycles that thin out vegetation. In whatSwetnam calls “the Smokey Bear effect,” we may have become morevulnerable to large, destructive burns.

Fires coming early, and often

As Westerling and Swetnam studied climate and fire recordsaround the West, however, they saw a disturbing pattern thatcouldn’t be explained by Smokey Bear. At least for parts of theWest, it was possible to link the current siege of big wildfires towarming temperatures. Climate data – which includes such poeticdetails as the early blooming of lilacs – suggested that spring wasarriving earlier. At higher elevations, early spring was causingearlier melting of winter snow. That meant forests were driersooner in summer, and more primed to burn if struck by lightningduring a July thunderstorm.

Last summer, Westerling, Swetnam, and their coauthors publishedtheir findings in Science magazine. Without pinning blame on the causes of thewarming trend, they reported that the West’s springs and summerswere indeed getting warmer, and that as a result, we wereexperiencing bigger fires, more fires, and longer fire seasons. Thelinks between climate and wildfires were clearest in the northernRockies and in the Sierra Nevada/southern Cascades.

As for Swetnam’s Southwest, he thinks that a combination ofwarming temperatures and fire suppression kindled conflagrationslike the 2002 Rodeo-Chediski fire. “The Rodeo was 10 times largerthan the next-largest forest fire the Southwest has had in 100years,” Swetnam says. “It made everybody say, ‘This is reallysomething different.’ “

Moving into harm’s way

Our wildfires are getting bigger and hotter just as we’re movingdeeper into fire-prone parts of the West. Between July 2005 andJuly 2006, Arizona was the nation’s fastest-growing state; Nevadawas second, Idaho third. In each of these states, much of thegrowth has occurred in what fire scientists call the wildland-urbaninterface – those once-rural zones that appeal because they offercheaper land prices and the chance to enjoy country living.

Says fire scientist Jan van Wagtendonk, “A lot of people think,Well, climate change doesn’t affect me – maybe I’ll get a bettertan. But extreme fire seasons affect homeowners directly.” LikeSwetnam, van Wagtendonk has spent a long career studying fires, andfrom his post with the U.S. Geological Survey’s Yosemite FieldStation in El Portal, California, he’s seen changes in the SierraNevada, including some animal species moving to higher elevationsand others moving into Yosemite National Park from lower ones. Andhe has seen fires like the 1996 Ackerson fire, the largest everrecorded in Yosemite.

As former president of the Association for Fire Ecology, a groupof more than 1,000 fire scientists and educators from around theworld, van Wagtendonk pushed hard for the organization to draftlast year’s declaration on climate change and fire management, itsfirst. Like Westerling’s Science article, the declaration skirtsthe issue of what is causing current warming trends – man ornature. But it states, firmly, that the warming trends andwildfires are linked, and that as a result, “extreme wildfireevents and a lengthened fire season may greatly increase the riskto human lives and infrastructures.”

Building fire-safe homes

How do we cope with living in a West that is more vulnerable tofires? First, most fire experts agree, we should plan on spending alot more money. In 2006, the Forest Service spent a record $1.5billion putting out fires, twice as much as budgeted. This year’scosts may well exceed that. As important, we’ll need to spend moreon fire prevention, from fire-education efforts to forestmanagement. Second, it’s more imperative than ever that we designand build homes and neighborhoods (and their landscaping) to betterwithstand wildfires.

And finally, we need to learn to live with uncertainty.Researchers like Westerling, Swetnam, and van Wagtendonk are thefirst to admit that there are many things about wildfire andclimate change in the West that we still don’t know.

“We don’t have all the answers,” says van Wagtendonk. “But thelonger we ignore climate change and its relationship with fire, themore dangerous it becomes. Uncertainty is not a reason for us notto act.”

INFO: Visit The National Interagency Fire Centerfor more about wildfires in the West.

MORE: Get tips onhow to create a defensible landscape and protect your home

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