Beetles take big bite out of forests

Jim Erickson, Rocky Mountain News

Published November 29, 2006 at midnight

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The number of Colorado lodgepole pines killed by bark beetles jumped nearly fivefold in 2006 as the explosive, decadelong bug epidemic continues to gain steam.

About 4.8 million lodgepoles were killed this year, up from roughly 1 million trees last year, according to Bob Cain, an entomologist with the U.S. Forest Service in Golden.

The lodgepole acreage under attack by mountain pine beetles jumped about 50 percent this year to 644,840 acres, up from 430,526 acres last year.

The new numbers, which are considered preliminary, come from aerial tree-damage surveys conducted this summer.

"We had a significant increase in both acres and even more so in intensity - meaning that on the acres impacted, a lot more trees died," Cain said.

"They're not slowing down at all," he said. "There's nothing really stopping these beetles."

Colorado's lodgepole pines are found mainly in the state's north- central mountains, at elevations between 6,000 and 11,000 feet. Many of the stands are more than a century old, with trees up to 80 feet tall.

The state's ponderosa pines are also under attack by mountain pine beetles, but "the big outbreaks are all in the lodgepole," Cain said.

Colorado has about 1.5 million acres of lodgepole-dominated forest, and about 43 percent of it is now infested.

A weeklong streak of bitterly cold weather might be able to stop the beetle plague. But a trend toward warmer Colorado winters - especially in the north-central mountains - makes that prospect seem unlikely.

"In the absence of some sort of extreme weather event, there's no reason for this infestation to stop until it's just run out of food," said Jan Burke, silviculturist for the White River National Forest, one of the state's hardest-hit regions.

The forest includes the Vail, Keystone, Arapahoe Basin, Breckenridge, Copper Mountain, Beaver Creek and Aspen ski resorts.

"We're going to see a virtual loss of mature lodgepole pine in the state of Colorado," Burke said. "There's going to be a very different look to our forests, and it is happening now."

The current mountain pine beetle epidemic began in the mid-1990s and exploded during the recent multi-year drought.

In a report issued Tuesday, a research team headed by Colorado State University's William Romme said the drought, combined with relatively mild winters and lots of old, densely packed trees, created a "perfect storm" for beetle outbreaks across much of Colorado.

In addition to the bark beetle problem in lodgepole and ponderosa pines, southwestern Colorado lost more than 9 million piñon pines to the piñon ips beetle in an outbreak that peaked two years ago.

Western bark beetles and root diseases killed more than 600,000 sub-alpine fir trees in the state last year. Spruce beetles infested 1.2 million Colorado trees in 2005 and appear poised to launch the next big bark beetle epidemic, according to the Colorado Forestry Advisory Board.

In the new report, Romme and his colleagues argue that the outbreaks now ravaging Colorado's forests are "similar in intensity and ecological effects to previously documented events in the Rocky Mountains."

In addition, the widely held belief that insect outbreaks set the stage for extreme wildfires "is not well supported, and may in fact be incorrect," Romme and his colleagues conclude in the 24-page report, titled "Recent Forest Insect Outbreaks and Fire Risk in Colorado Forests: A Brief Synthesis of Relevant Research."

The report is posted at www.cfri .colostate.edu/docs/cfri_insect.pdf.

Stopping a mountain pine beetle epidemic in its tracks requires a cold snap with temperatures hitting 30 to 35 degrees below zero for several days to a week, said forester Andy Cadenhead of Routt National Forest.

North-central Colorado used to experience that kind of biting cold "on a pretty regular basis," but such events are becoming increasingly rare, said University of Colorado climatologist Klaus Wolter.

Wolter just completed an analysis of Colorado temperature trends during the past 50 years. During that time, the state's average annual high temperature increased by about 1 degree Fahrenheit, while the average low temperature rose by 2 degrees.

North-central Colorado warmed faster than any other part of the state during the past 50 years.

There, the average annual high temperature rose 2 degrees, and the average low temperature shot up more than 4 degrees, Wolter said.

"The fact that the minimum temperatures have gone up so much makes it much less likely that you're going to get the cold needed to stop a big (insect) outbreak," he said.

Mountain pine beetle attack

• Number of Colorado lodgepole pine trees killed by mountain pine beetles

4.8 million in 2006

1 million in 2005

• Colorado lodgepole pine acres under attack by mountain pine beetles

644,840 in 2006

430,526 in 2005

• Acres of lodgepole-dominated forest in Colorado:

1.5 million

43 percent of lodgepole forest infested by mountain pine beetles

ericksonj@RockyMountainNews.com or 303-954-5129

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