How The Smokey Bear Effect Led To Raging Wildfires

NPR: How The Smokey Bear Effect Led To Raging Wildfires

Yet another story of the unintended consequences.

… Growth rings tell how old the sectioned tree was. But when Swetnam holds up one, he points to something else: fire scars. They're black marks, about the size of a fingernail clipping, left by fires. …

… Scars from thousands of sections show how often fires burned in the Southwest. It was every five or 10 years, mostly — small fires that consumed grass and shrubs and small seedlings, but left the big Ponderosa pine and Douglas fir just fine. This was the norm.

Then something happened.

"Around 1890 or 1900, it stops," Swetnam says. "We call it the Smokey Bear effect."

Settlers brought livestock that ate the grass, so fires had little fuel. Then when the U.S. Forest Service was formed, its marching orders were "no fires."

And it was the experts who approved the all-out ban on fires in the Southwest. They got it wrong.

That's the view of fire historian Stephen Pyne.

"The irony here is that the argument for setting these areas aside as national forests and parks was, to a large extent, to protect them from fire," Pyne says. "Instead, over time they became the major habitat for free-burning fire."

So instead of a few dozen trees per acre, the Southwestern mountains of New Mexico, Arizona, Colorado and Utah are now choked with trees of all sizes, and grass and shrubs. Essentially, it's fuel.

And now fires are burning bigger and hotter. They're not just damaging forests — they're wiping them out. Last year, more than 74,000 wildfires burned over 8.7 million acres in the U.S.

That included the huge Wallow fire in Arizona.

"It burned more than 40,000 acres in the first eight hours," says Swetnam, the tree ring expert. "A tornado of fire."

Fires in the Southwest have been getting bigger and bigger over the past two decades.

"Now the fire behaviors are just off the charts," Swetnam says. "I mean, they are extraordinary. Actually, I think in some cases, they're fire behavior that probably these forests haven't seen in millennia or maybe even tens of thousands of years." …

… "The choice is not whether or not these forests burn," Armstrong says. "The choice is how they burn. What kind of intensity are we going to see those burn at?" …