From the Summit County Citizens Voice (Bob Berwyn):
Tree mortality was reported across 6.4 million acres in 2011, down by nearly half from the 12-million acre peak in 2009, but still significantly higher than during the 1990s, when tree mortality stayed under 1 million acres per year between 1990 and 2001. Acres of forests with dead trees due to the mountain pine beetle declined from 6.8 million acres in 2010 to 3.8 million acres in 2011 in western states, according to a report released by the U.S. Forest Service last week. Mountain pine beetles accounted for about 59 percent of the total damage, the agency said.
This marks the second straight year with reduced mortality rates after steady increases between 2006 and 2009. Although Forest Service surveyors attribute some of the reductions to fewer available lodgepole pines, ponderosa pine and high-elevation white bark pine are still at risk. “Native insects and diseases run in cycles, and right now we are grateful the trend is downward,” said U.S. Forest Service Chief Tom Tidwell. “While the news is good, we are certain to continue to face challenges, such as the effects of climate change and the introduction of invasive species.”
Despite the decline, pine beetles still resulted in more than 3.8 million acres of mortality in 2011, with the biggest affected areas in Colorado, Montana, Idaho and Wyoming.
The most widespread pine beetles damage was in Montana, at nearly 1 million acres, with Colorado, Idaho and Wyoming all reporting between 700,000 and 800,ooo acres of pine beetle mortality in 2011.
In Colorado, mountain pine beetles continued to cause damage, with most of the mortality now reported east of the Continental Divide, including ornamental plantings in downtown Denver. The Forest Service said the insects are spreading readily into lower elevation ponderosa pine forests in Bouler and Larimer counties. West of the Continental Divide, mortality continues to spread around Aspen and Vail. The bugs area also starting to attack limber pines and Rocky Mountain bristlecone pines.
Forest experts said drought-induced stress and wind-downed trees helped fuel the surge in spruce beetles in the region. Spruce beetle outbreaks in Colorado include the Grand Mesa, the Wet Mountains and especially the eastern San Juans, where the bugs have marched into the headwaters of the Rio Grande and continued into the southern portions of the Gunnison National Forest.