The falling forest

The falling forest

15 January 2006

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United States — Nearly four years after the Missionary Ridge Fire burned more than 70,000 acres, the trees it killed and left standing are increasingly likely to fall, posing a potential danger to motorists and forestusers.

Mike Johnson with the U.S. Forest Service in Durango inspects a pine tree near Vallecito Reservoir. The tree was burned by the 2002 Missionary Ridge Fire.

The fire left many trees standing with weak root systems, according to Philip Kemp, a forester with Dolores Public Lands. Trees may look OK but have little holding them up. And those at the lowest elevations are most susceptible to falling.

“The most unstable species are those at the lower elevations of the burned area, where visitors or property are concentrated,” Supervisory Forester Steve Hartvigsen wrote in a letter prepared at a citizen’s request.

Ponderosa pine, a tree species particularly likely to fall this year and next, line heavily traveled roads in the fire area. Mike Johnson, a U.S. Forest Service forester, said that an unsuspecting driver could run into a fallen tree.

“Our concerns are particularly where the fire got close to the roads and common-use areas,” he said.

Numerous dead ponderosa pines line County Road 250 and County Road 501 near Vallecito.

Research conducted by the U.S. Forest Service in the Northern Rockies found that ponderosa pines fall in increasing frequency four to five years after a forest fire. The annual fall rate for ponderosa pines rises 20 percent above normal four years after a fire and 53 percent five years after a fire.
“These trees that are fire-killed and don’t have any needles are going to be falling over with a greater frequency,” Johnson said.

Homeowners and government agencies have removed many hazardous trees, but some remain. Foresters worry that because much of the fire damage has been fixed, people could falsely believe that the danger from falling trees has passed.

“The public, in general, could be lulled into believing that the dangers of the fire and post-fire era are diminishing,” Hartvigsen wrote. “Yet, the dangers of tree-fall are likely to continue for many years to come.”

The only death during the Missionary Ridge Fire came from a falling tree. Alan Wyatt, a 51-year-old father and husband from Oregon, was killed while trying to knock down another tree to make the area less dangerous for firefighters.

Strat Stepan, a concerned citizen who lives in the burned area, wants the county and landowners to remove the remaining dangerous trees. But the county has received an opinion from Dan Ochocki of the Colorado Forest Service noting the difficulty of knowing which trees pose a danger and when and how they might fall, according to Commissioner Sheryl Ayers.

“We have not decided that there’s any action on our part needed,” Ayers said.

Nevertheless, hikers, hunters and others who play in the forest should exercise caution in burned areas, Johnson said.

“If it’s a windy day, you may want to postpone your trip,” he said. “Folks need to be careful.”


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