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Fire officials in a tri-county area said they’re seeing extreme fire behavior in areas with trees killed by the mountain pine beetle.

Sonny Stiger, a fire behavior analyst, told a group gathered in Helena Wednesday for a forum on the impact of the rice-size beetles, that he’s seeing flame lengths of 200 to 300 feet in places they wouldn’t expect it; they’re experiencing unusual embers being thrown farther ahead of fires and groups of treetops torching; and ponderosa pines’ low-hanging dead branches are creating ladder fuels that allow blazes to spread more rapidly than in the past.

“The kind of things we’re dealing with is one fire grew to three acres in two minutes, 10 to 15 acres in the next eight minutes — that’s moving — and over 100 acres in the first hour,” Stiger said. “So we are experiencing unusual, extreme fire behavior now.”

During the past decade, mountain pine beetles have devoured about 9 million acres of forest in the Rocky Mountains from Colorado to Montana, and about 40 million acres in British Columbia. They kill mainly lodgepole and ponderosa pine trees by burrowing into them to lay eggs; when the eggs hatch, the young “girdle” the tree by eating around it in horizontal circles, cutting off the flow of nutrients, before they fly to new trees and re-create the deadly cycle.

In Montana, the 980,000-acre Helena National Forest has been particularly hard hit by the beetles, with dead or dying trees on 550,000 acres.

Brad McBratney, the fire management officer for the Helena and Lewis and Clark national forests, added they’re also seeing wildfires rage when they typically wouldn’t expect it. He said they used to use the 80-20-20 rule: that fires won’t transition to out-of-control burns if the temperatures are lower than 80 degrees, the relative humidity is more than 20 percent, with winds less than 20 mph.

But the Davis fire, which started out as a controlled burn last year near Canyon Creek and exploded into a multi-million-acre wildfire before it was extinguished, transitioned when temperatures were in the 70s and winds were only 7 to 9 mph in the area.

“We don’t have models that can make predictions anymore,” McBratney said. “Our old rules don’t work anymore. We need more research and still need the media and the Pat McKelveys of the world (who helps homeowners create defensible spaces) to make sure the public is informed and makes good choices on the landscape.”

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Greg Archie with the state Department of Natural Resources ticked off a list of 13 fires fought during the past three years in Lewis and Clark, Jefferson and Broadwater counties, during a time he said most people considered “slow” fire seasons.

His biggest fear with the changing fire activity involves firefighter safety. Archie said they’re experiencing ponderosa pine trees 16 inches in diameter snapping in half 20 feet above the ground, surprising those on the ground. He noted that firefighters have to be even more vigilant in watching their escape routes, in case falling trees cut those off, and have to realize that the potential for fires to grow large, quickly, seems to be greater.

“We are scratching our heads trying to figure out how to tame this beast,” Archie said. “We need to build these science-based hypothetical pictures until we get enough experience to get that slide show (of how a fire will behave) established in our minds.”

Reporter Eve Byron: 447-4076 or eve.byron@helenair.com

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