Report defies conventional wisdom on pine beetles and wildfirePosted: April 11, 2012
The threat comes from the tiny mountain pine beetle, only not in the way most people think. Beetle-killed trees have undermined decades of fire behavior research – because before they burn, dead trees may silently topple. And an unburned falling tree will kill you just as surely as a burning one.
“Now my big concern is how do we approach the thing,” Gage said. “How do we get people into a fire that’s in the middle of beetle-kill safely? Hike them in? Fly them, or put heavy equipment in front of them? And if we can’t get people in safely, how do we engage when the fire comes out?”
Gage has spent 42 years fighting fire. In the last two or three years, he’s seen things that drain away the confidence he’s placed in his tactical handbooks. The reports from 2011’s Saddle and Salt fires in the southern Bitterroot Mountains told of beetle-killed stands on flat ground burning as if they were on steep hillsides or high winds. Colorado forests have seen more than 60 trees a minute blow down in winds of less than 15 mph.
“We’re always thinking about what-if?” Gage said. “If we’ve got an 80 percent chance of success, what does 20 percent failure look like?”
The impact of mountain pine beetles looks very different for environmentalists like Matthew Koehler of the Wild West Institute. Koehler recently circulated a February 2012 Fire Science Digest report on bark beetles, highlighting the following summary:
“Are the beetles setting the stage for larger, more severe wildfires? And are fires bringing on beetle epidemics? Contrary to popular opinion, the answer to both questions seems to be ‘no.’ ”
“We feel as if a lot of the conventional wisdom about bark beetles and wildfire is incorrect,” Koehler said. “The latest science and research coming out seems to support the notion wildfire and beetles are critically important to forest health. We would encourage forest managers and politicians to embrace these natural processes, instead of fear-based rhetoric that leads to justification for more logging or road-building or resource development.”
One of the biggest recent timber sales on the Helena National Forest involves creating a 300-foot safety zone along most secondary roads through Forest Service lands. That sale was predicated on the risk of beetle-killed trees burning or falling on the roads more than on its potential timber value.
Koehler said he understood the reasoning behind clearing trees that threaten campgrounds at Georgetown Lake. But he worried the same reasoning might be used for backcountry logging where the beetle-kill might provide improved wildlife habitat.
Whether the question is tactical – how best to deploy a Hot Shot crew on a fire front? – or managerial (how to justify a timber sale), the mountain pine beetle has chewed its way through mounds of what we used to call normal.
“When people look across a landscape like Lookout Pass and see a lot of red needles, they think they’re looking at a tinderbox,” said fire ecologist Robert Keane at the Missoula Fire Science Laboratory.
The factors he sees defy such simple assumptions.
Current research on beetle-killed trees depends a lot on time and space. Time-wise, it appears a lodgepole pine burns easier within three years of death by pine beetles – when its needles are still green or have turned red – than a live lodgepole. But it’s very hard to tell a dead-but-green “fader” tree from a live one, until it burns.
And Keane said dead trees with needles, regardless of color, appear to burst into dangerous crown fires much easier than live stands. And while firefighters used to simply measure the moisture content of dry wood to determine how fast it could catch fire, it turns out chemical factors like sugars are even more important.
Once the needles fall, after four or five years, the crown-fire hazard falls too. Except that around eight years after death, those “gray ghosts” start toppling. That’s the new problem incident commanders like Gage worry about. And it’s not just trees falling on firefighter’s heads. It’s the difference between having one ton of dry needles per acre on the ground or 100 tons of dry firewood.
“The issue is resistance to control.” Gage said. “When you have a lot of fuel on the ground, it’s like having many logs in your fireplace instead of one. It puts out more heat on the ground. It exponentially adds to the number of people you need. It takes more water. You need more saws to clear paths. It changes where you can put your safety zones.”
Space-wise, the question is where? Keane said a lot of research in fire behavior in Yellowstone National Park doesn’t apply elsewhere, because almost no other place has Yellowstone’s combination of high altitude and volcanic soils.
And those toppling trees? Keane said in parts of British Columbia, foresters have found whole stands of beetle-kill that collapsed into pick-up sticks just three years after infestation. You can’t cut and paste a study in one part of the Rocky Mountains to another and expect identical results.
Once the needles have fallen, sunlight and rain can foster low-growing shrubs. In some places, that provides new ladder fuels which can ignite the dead trees. In others, the moist shrubs lower the chance of a fire getting going.
Fire Sciences Laboratory program manager Colin Hardy said pine beetles have upended whole shelves of assumptions his researchers have depended on for decades.
“The models everybody uses on an operational basis were developed in 1972,” Hardy said. “They were designed for firefighter safety and fire suppression of surface fires.”
Those models don’t account for crown fires, climate change, population changes, backcountry subdivisions – let alone mountain pine beetle infestations.
Current studies of beetle effects have been running for 15 years, and they may need 15 more to reveal conclusive answers. It’s like being asked how many ears of corn will come from the kernel you planted yesterday.
And that’s just the beetle questions involving lodgepole pine. Conditions are different for ponderosa pine, or for stands of spruce and Douglas fir infested with spruce budworm. Then there are the new developments in physics that may explain why fires react to different wind conditions or terrain features.
In the corner of Hardy’s conference room stands a refrigerator-sized box with a label that reads “Unisys ES-7000.” It’s a mainframe computer with a once-whopping 32 gigabytes of memory. When it was installed, it chewed through fire behavior models that used to take 38 days of computing in just 17 hours.
“Now our new Cray supercomputer is two orders of magnitude faster,” Hardy said. “It can run that model in about an hour. It’s still not enough.”