Author and ecologist George Wuerthner will present a free lecture in Helena Thursday on wildfires and bark beetles, and the ecological value of dead trees.

Wuerthner has long argued that dead trees are critical to a healthy forest ecosystem and don’t necessarily need to be removed from a forest to lessen the danger of catastrophic wildfires.

He was in Mexico last week, but in an e-mail interview Wuerthner said he visited Helena this summer and is aware of the discussions taking place regarding the thousands of trees killed by mountain pine beetles on Mount Helena, Mount Ascension and in the nearby Helena and Beaverhead-Deerlodge national forests.

The Helena City Commission recently set aside $100,000 to remove dead or hazardous trees on the urban-wildland interface along the mountainsides surrounding the city. In the nearby forests, both green and dead trees are being logged at popular campgrounds like Park Lake, at trailheads and along travel corridors in an effort to keep them from falling onto people and vehicles.

Wuerthner said logging as a preventive measure might slow down the infestation, but research shows that anywhere from 50 to 80 percent of the trees need to be removed if conditions are ripe for a major attack.

“So you have to ask yourself, what’s the point? That is the Vietnam approach to forestry — kill all the trees so you can ‘save’ them,” Wuerthner wrote, adding that logging isn’t benign and is expensive. “So you further have to ask whether the costs in terms of ecosystem impacts (the spread of weeds on logging roads for instance) are worth the presumed benefits.”

He also questions logging as a solution to the current beetle infestation because not every tree will be threatened by them, and no one can say for sure if foresters will pick the right trees to remove.

The same holds true for logging to prevent wildfires, Wuerthner said.

“... fires do not burn all trees, nor do they occur every year. So you might log an area in anticipation of a fire, but that place will never burn because the conditions for a fire do not occur,” Wuerthner wrote.

And Wuerthner argues that just because trees are dead doesn’t necessarily mean that they are more likely to burn than live trees.

“Live trees have resins in their needles and branches that make them very flammable,” Wuerthner wrote, adding that these are the “flashy” fuels that are the dominant fuel in a fire. “So once a tree is killed by pine beetles, its flammability is high for a year or two, but once the needles and small branches fall off in winter, these trees are actually less flammable. ... Then there is a lull of 15-30 years when the likelihood of a fire goes way down.”

The fire danger rises for a decade or so, Wuerthner said, not because of dead trees. Rather, the small trees growing in the forest create a ladder to the remaining live trees. Once the canopy closes, he adds, the flammability goes down again for many more decades.

Wuerthner’s lecture is from 7 to 9 p.m. Thursday at the University of Montana-Helena, 1115 N. Roberts, in Room 125.

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