The New York Times has an article about the effect of bark beetles on fire. Here is an excerpt:
DENVER — Summer fire seasons in the great forests of the West have always hinged on elements of chance: a heat wave in August, a random lightning strike, a passing storm front that whips a small fire into an inferno or dampens it with cooling rain.
But tiny bark beetles, munching and killing pine trees by the millions from Colorado to Canada, are now increasingly adding their own new dynamic. As the height of summer fire season approaches, more than seven million acres of forest in the United States have been declared all but dead, throwing a swath of land bigger than Massachusetts into a kind of fire-cycle purgatory that forestry officials admit they do not yet have a good handle on for fire prediction or assessment.
Dead trees, depending on how recently they died, may be much more flammable than living trees, or slightly more flammable, or even for a certain period less flammable. The only certainties are that dead forests are growing in size and scale —22 million more acres are expected to die over the next 15 years — and that foresters, like the fire-tower lookouts of old, are keeping their eyes peeled and their fingers crossed.
“There’s just a lot more fuel in those dead forests available to burn,” said Bob Harrington, the Montana state forester, who is focusing additional resources this summer on a three-million-acre zone of beetle-infested forest from Butte to Helena.
More than 100,000 people live in that area, and Mr. Harrington said that although fire forecasts for Montana, as in most of the West, called for only an average fire season, dead forests do not play by the rules. They can dry out much faster in heat, without living tree tissue to hold water.
Other beetle watchers say the nightmare of a severe fire season concentrated in the dead-forest zone running along the spine of the Rocky Mountains has, so far, been averted. In Colorado, a combination of deep snows last winter followed by a wet spring has kept fire danger low. But scientists say that recent winters have also lacked the stretches of deep cold — 20 to 40 degrees below zero — that can check the insects’ spread.
“Right now, in our neck of the woods, we’re really wet,” said Mary Ann Chambers, a spokeswoman for the federal Forest Service’s bark beetle incident management team for a five-state region that includes Colorado. “We seem to have dodged the bullet — again.”
The government’s four-month fire forecast issued in June called for a potentially more active fire season in central Washington and Northern California. But most of the rest of the region, like the country, is expecting normal or below-normal conditions.
The Forest Service proposed a tree-thinning program of fire protection just outside Helena, for example, in 1997, when the forest was green and healthy. The project was stalled by litigation for 12 years until earlier this year, when a federal appeals court in San Francisco finally ruled for the Forest Service that the thinning plan could proceed.
“In the interim, the bark beetle entered the picture,” said Duane Harp, a district ranger in the Helena National Forest. “Now 90 percent of the trees when we started the project are dead.”
Government lawyers said the Forest Service could be sued again if it went ahead with the old plan on a now fundamentally altered forest, Mr. Harp said, so foresters are reassessing the impact of thinning in a dead forest.