Is Wildfire Severity Really Getting Worse?
It might seem like fire season is as bad as it's ever been. But there's a group of researchers who question that prevailing wisdom.
The drumbeat about wildfires going from bad to worse reaches all the way to the White House. A few days ago, President Obama's science advisor John Holdren said, "Climate change has been making the fire season in the United States longer and, on average, more intense."
Now contrast that with three fresh science papers from separate institutions. Each makes the case that forest fires in the West today burn less than in historical times.
One of the co-authors is Dominick DellaSala, chief scientist at the Geos Institute in Ashland, Oregon.
"If we use the historical baseline as a point in time for comparison, then we have not seen a measurable increase in the size or the severity of fires," DellaSala said. "In fact, what we have seen is actually a deficit in forest fires compared to what early settlers were dealing with when they came through this area."
DellaSala said the timeframe you choose makes a big difference. If you just look at recent decades, there is a notable rise in acres burned.
In his narration of a White House video, Holdren honed in on the modern era as he summarized key findings of a National Climate Assessment released in May. "Longer, hotter, drier summers are projected to continue to increase the frequency and intensity of large wildfires in the United States," Holdren said. "In the Western U.S., the average annual area burned by large wildfires has increased several fold in recent decades."
DellaSala agrees climate change has the potential to bring more droughts and thus more wildfires. But the prospect of more conflagrations does not alarm him as much as it does others.
"If you look at it just from an ecological standpoint, there are many species that depend on fire," DellaSalla explained. "Actually when a fire moves through a forest, it will restore habitat for lots of different bird species and other wildlife that depend on a severe burn."
"The problem now is we've got a lot more people living in the so-called wildland-urban interface. So there are property and human life issues," DellaSala acknowledged.
DellaSala contributed to an analysis of wildfire prevalence in ponderosa pine forests published earlier this year in the journal PLoS One. The lead author was Dennis Odion of the University of California Santa Barbara.
Separately, a team led by U.S. Forest Service scientist Hugh Safford at the Pacific Southwest Research Station published a study on forest fire prevalence in California. The researchers found that fires in the southern Cascades and Sierra Range are now less frequent than in historical times.
University of Wyoming geographer William Baker looked specifically at Sierra Range forests in a paper published last month in the peer-reviewed journal Ecosphere. It described evidence for an "extensive severe fire" regime historically.
To reconstruct the fire history of the American West, researchers mine observations of early settlers, archival General Land Office survey data, early newspaper clippings or delve further back by dating charcoal records or pollen samples.
Fire suppression by settlers and government agencies began in earnest after the Great Fire of 1910, also known as the Big Burn, which scorched parts of northern Idaho, Montana and eastern Washington.