Anyone who has seen the aftermath of a wildfire on television - or, more harrowingly, in person - knows its risks. The ghostly chimneys of vanished houses, the melted frames of automobiles in blackened driveways - these aren't images you forget. This is why the West tends to remember its fires with the fearful reverence in which 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 - a growing number of researchers believes that global warming is, in the West, generating wildfires that are bigger and more dangerous than ever before. And the fire threat is growing just as we're moving 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 study fire. "My maternal grandfather was an L.A. County fireman," he says, "and before that, a forest ranger. My mother is fascinated by fire. When I was a kid, we spent every summer in the Sierra, and she would pile us into a car and drive out to watch all the big fires - at a safe distance, of course."
All this was, perhaps, perfect preparation for Westerling's investigation into the link between fires and climate. Over the last decade, the West has experienced some of the largest fires in documented history - "mega-fires," ones that burn more than 100,000 acres. Like this summer's Milford Flat fire in Utah (the largest in state 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. This June's Angora fire, which destroyed 242 homes near Lake Tahoe's California side, struck a month before the traditional season for big fires in the Sierra Nevada. The question is: Are we getting these bigger, hotter, earlier, more frequent wildfires because our climate is getting warmer?
But arriving at an answer is complicated. You need to determine how the West's 2007 summer temperatures compare with temperatures in the summer of 1957, and 1857, and 1457. You need to know how 2007's wildfires compare in size and intensity with the wildfires of the past. Acquiring this data - from climate records, tree rings, soil samples, pioneer journals - is not easy. And then you need to understand how the two sets of data relate.
"I was skeptical about being able to see a link between increased fires and warmer temperatures," says Thomas Swetnam, one of Westerling's co-researchers. As director of the University of Arizona's Laboratory of Tree-Ring Research, Swetnam has spent his entire career studying the relationship between forests and climate.
There is an additional complexity, Swetnam explains, and that's us. Even ignoring our possible effects on climate, we've already had a big impact on fire in the West. We start wildfires, sometimes accidentally - and sometimes on purpose.
But at the same time, over the last century we've spent vast amounts of manpower and money to prevent and suppress wildfires, interrupting natural fire cycles that thin out vegetation. In what Swetnam calls "the Smokey Bear effect," we may have become more vulnerable to large, destructive burns.
Fires coming early, and often
As Westerling and Swetnam studied climate and fire records around the West, however, they saw a disturbing pattern that couldn't be explained by Smokey Bear. At least for parts of the West, it was possible to link the current siege of big wildfires to warming temperatures. Climate data - which includes such poetic details as the early blooming of lilacs - suggested that spring was arriving earlier. At higher elevations, early spring was causing earlier melting of winter snow. That meant forests were drier sooner in summer, and more primed to burn if struck by lightning during a July thunderstorm.
Last summer, Westerling, Swetnam, and their coauthors published their findings in Science magazine. Without pinning blame on the causes of the warming trend, they reported that the West's springs and summers were indeed getting warmer, and that as a result, we were experiencing bigger fires, more fires, and longer fire seasons. The links between climate and wildfires were clearest in the northern Rockies and in the Sierra Nevada/southern Cascades.
As for Swetnam's Southwest, he thinks that a combination of warming temperatures and fire suppression kindled conflagrations like the 2002 Rodeo-Chediski fire. "The Rodeo was 10 times larger than the next-largest forest fire the Southwest has had in 100 years," Swetnam says. "It made everybody say, 'This is really something different.' "
Moving into harm's way
Our wildfires are getting bigger and hotter just as we're moving deeper into fire-prone parts of the West. Between July 2005 and July 2006, Arizona was the nation's fastest-growing state; Nevada was second, Idaho third. In each of these states, much of the growth has occurred in what fire scientists call the wildland-urban interface - those once-rural zones that appeal because they offer cheaper 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 better tan. But extreme fire seasons affect homeowners directly." Like Swetnam, van Wagtendonk has spent a long career studying fires, and from his post with the U.S. Geological Survey's Yosemite Field Station in El Portal, California, he's seen changes in the Sierra Nevada, including some animal species moving to higher elevations and others moving into Yosemite National Park from lower ones. And he has seen fires like the 1996 Ackerson fire, the largest ever recorded in Yosemite.
As former president of the Association for Fire Ecology, a group of more than 1,000 fire scientists and educators from around the world, van Wagtendonk pushed hard for the organization to draft last year's declaration on climate change and fire management, its first. Like Westerling's Science article, the declaration skirts the issue of what is causing current warming trends - man or nature. But it states, firmly, that the warming trends and wildfires are linked, and that as a result, "extreme wildfire events and a lengthened fire season may greatly increase the risk to human lives and infrastructures."
Building fire-safe homes
How do we cope with living in a West that is more vulnerable to fires? First, most fire experts agree, we should plan on spending a lot more money. In 2006, the Forest Service spent a record $1.5 billion putting out fires, twice as much as budgeted. This year's costs may well exceed that. As important, we'll need to spend more on fire prevention, from fire-education efforts to forest management. Second, it's more imperative than ever that we design and build homes and neighborhoods (and their landscaping) to better withstand wildfires.
And finally, we need to learn to live with uncertainty. Researchers like Westerling, Swetnam, and van Wagtendonk are the first to admit that there are many things about wildfire and climate change in the West that we still don't know.
"We don't have all the answers," says van Wagtendonk. "But the longer we ignore climate change and its relationship with fire, the more dangerous it becomes. Uncertainty is not a reason for us not to act."
INFO: Visit The National Interagency Fire Center for more about wildfires in the West.