Published September 18, 2012
Phil Taylor, E&E reporter
Published: Tuesday, September 18, 2012
The frequency of larger wildfires on Forest Service lands in the West has significantly increased over the past 40 years and is likely to continue to increase as temperatures rise and winter snowpack shrinks in the West, according to a new report from a Princeton, N.J.-based scientific organization.
The report by Climate Central warns the 2012 wildfire season — which, at 8.4 million acres, is already the second largest this decade with nearly two months of the season remaining — may soon be the new normal.
Compared to average years in the 1970s, each year of the past decade saw seven times more fires greater than 10,000 acres and almost five times more fires larger than 25,000 acres, according to the report. In addition, wildfires today are burning twice as many acres annually than in the 1970s.
Fires this season burned more acres on average than any other year this decade, according to the National Interagency Fire Center.
“What defines a ‘typical’ wildfire year in the West is changing,” the report says. “In the past 40 years, rising spring and summer temperatures, along with shrinking winter snowpack, have increased the risk of wildfires in most parts of the West.”
The study also cites a National Research Council finding that for every 1.8 degree Fahrenheit increase, the area burned by wildfires in the West could quadruple. By the middle of the century, summer temperatures in western North America could increase as much as 9 degrees, the report notes, citing the Intergovernmental Panel on Climate Change.
Higher temperatures can cause earlier snowmelt, reducing the amount of moisture in the ground and creating conditions ripe for larger fires, the report said. In the past four decades, years with higher spring and summer temperatures typically also have had the largest wildfires.
And wildfires are burning both earlier and later in recent years than they were in the 1970s, adding 75 days to the average season.
“What we’re seeing now in the northern Rockies is a consequence of what starts all the way back with the spring snowmelt,” Steven Running, a professor in the University of Montana’s College of Forestry and Conservation, said during a conference call with reporters this afternoon to discuss the report’s findings. He was not involved in writing the report.
Running described the valleys surrounding Missoula, Mont., as full of smoke. Today is historically the area’s first fall frost, he said.
“This is a clear illustration of the longer fire seasons that we now have,” he said. “We have a landscape that’s vulnerable for a longer period of time. All it takes is an ignition source, and off to the races you go.”
Running said federal land managers should focus on breaking up the continuity of available fuels through management of natural fires and targeted salvage harvesting, in addition to creating buffer zones around towns.
Jennifer Marlon, a postdoctoral fellow at the Yale School of Forestry and Environmental Studies, said no amount of thinning will fireproof forests, which often depend on fires to regenerate. Rather, it’s important to educate the public about building defensible space around their homes, clearing dead brush and using flame-resistant building materials.
“I can’t think of anything that’s going to slow down this trend other than a sudden shift to cooler weather conditions and shorter summers,” said Marlon, who also was not involved in the report’s writing.
The report also notes that the spread of mountain pine beetles and other insects in the West is a “potential driver” in wildfire activity. However, while insect-driven mortality may increase fuel loads in the short term, recent research suggests that in the long term, beetle-killed forests may be no more susceptible to fire than healthy ones, it said.
Climate Central, a nonprofit group of scientists and journalists, says it does not advocate any specific legislation or policies. But its writers have urged immediate action to avoid the worst consequences of climate change.
The Forest Service this season has been attacking wildfires more aggressively, including ones far from communities, citing unusually dry conditions and tight budgets.
The Obama administration plans to accelerate tree thinning to reduce the risk of catastrophic wildfires but is limited by funding, a lagging lumber market and occasional environmental lawsuits.
