With the Rim Fire building toward the national treasures of Yosemite’s great sequoia groves, the problems of a century of forest fire suppression (frequently discussed here) are getting fresh attention. Andy Revkin at the New York Times’ Dot Earth late last week offered up a conversation with the University of Arizona’s Tom Swetnam and others about the problem. As Swetnam explains, fire suppression provided the fuel (in the form of great accumulations of woody biomass that used to routinely burn in frequent low-intensity fire). Then drought and a warming climate came along:
Although fuel/forest changes since the surface fire regime disruption 100-150 years ago is striking, the recent very large, very high intensity/severity fires in pine-dominant and mixed conifer forests can not be attributed solely or even primarily to these changes. Many Southwestern forests, for example, were already choked by thousands of small trees and dead fuel accumulations by the 1950s and 1960s…. Some large high severity fires occurred in these areas during the 1950s drought, and subsequent droughts, but the largest total areas burned in forests were an order of magnitude smaller than the largest fires today. The combined effects of warming and extreme dryness of the atmosphere and fuels, combined with the extraordinary fuel accumulations are “exaggerating” these fires.
Journal readers may recognize Swetnam’s name. He’s a frequent visitor to our pages, having grown up in Jemez Springs and fought fires as a young man in the Gila before moving to Tucson and becoming one of the southwest’s preeminent forest and fire ecologists:
The buildup of fuel, combined with drought and rising temperatures in a warming world, have turned fire in the mountains where he grew up into something completely different.
Las Conchas, the 2011 fire that at the time was the largest in recorded New Mexico history, marked a turning point. In its first day, it burned 10 times the area in the entire Cebollita fire of 1971. It spread so hot and so destructively that, after a post-fire visit, Swetnam described the landscape as “nuked.”
“No firefighter, I think, in the Southwest has seen that kind of fire behavior,” Swetnam said.
Here’s my colleague Pat Vasquez-Cunningham’s video piece on Swetnam and fire: