Volatile weather patterns marked by shortened winters, stifling heat waves and prolonged droughts. New housing developments encroaching on fire-prone lands. Shrinking budgets for fire-prevention measures.
That dangerous combination of factors helps explain the increasingly voracious wildfires that have ripped through the western United States in recent years, say scientists, lawmakers and historians.
While the deaths of 19 firefighters Sunday in Arizona marked the most lethal firefighting incident in generations, the 8,400-acre blaze that led to the tragedy has become more the norm than the exception.
"On average, wildfires burn twice as many acres each year as compared to 40 years ago. Last year, the fires were massive in size, coinciding with increased temperatures and early snow melt in the West," U.S. Forest Service Chief Tom Tidwell told lawmakers on Capitol Hill last month, adding, "The last two decades have seen fires that are extraordinary in their size, intensity and impacts."
Opinions differ on the precise reasons for the phenomenon. But broad agreement exists that climate change, coupled with economic development and state and federal policies on fire prevention, has played a significant role in shaping the fires raging across Western landscapes.
"This is the cost of how we live today," said Stephen Pyne, a professor in the School of Life Sciences at Arizona State University and a well-known fire historian. "Context does matter. Everything that's out there, fire reacts to. . . . How we develop things, what kind of vegetation we have, how we live on the land, what fire protection measures we take."
The paradox of destructive wildfires of recent years is that the West actually suffers from a "fire deficit," Pyne said.
"We're getting large, high-intensity fires where they shouldn't be," he said. "In an ideal world, we would get three or four times more fires than we're getting, but they would be on a smaller scale. More landscape, but less intensity. We have too many of the wrong kind of fires."