Vail, CO Colorado

SUMMIT COUNTY - A distinct rise in temperatures during the last 100 years is probably the single biggest factor in the recent outbreak of mountain pine beetles and other tree-killing insects across the West, a Colorado State University forest researcher said during Thursday's meeting of the Summit Pine Beetle Task Force.

"It's quite startling and unsettling to be living through this," said Tania Schoennagel, adding that the severe drought of 2002 seemed to coincide with an intensification of current beetle epidemic.

Schoennagel showed a graph from the National Oceanic and Atmospheric Administration's historical climate network that showed a clear rise in temperatures as measured at the Dillon station during the past century.

For some reason, that warming trend is more pronounced in north-central Colorado than in any other part of the state, Schoennagel said.

The cold snap at the end of November wasn't nearly cold enough or long enough to significantly slow the spread of the bugs. At least a week with temps dropping to minus-40 degrees each night is needed to freeze the larvae, she explained.

Schoennagel said there hasn't been much research to see if mountain pine outbreaks in the past have coincided with other periods of relatively warmer temperatures. She said there were more western bark beetles during a 1980s dry spell than there are now.

What is clear from some recent research is that intensive, long-term and widespread logging of pine forests in parts of British Columbia have not had any effect on the spread of pine beetles . Those findings may call into question the assumption that Colorado can log its way back to healthy forests.

Schoennagel also tackled the widely held conventional wisdom that past fire suppression is a significant factor in the current beetle outbreak.

"I can say with pretty good certainty that this is not an artifact of fire suppression. These forests were dense 100 years ago, they were dense 500 years ago," she said.

Longer intervals between fire may actually result in less dense forests, as individual trees die from various causes, she said.

A cycle of extreme drought in the late 1800s was followed by large fires, which led to the current forest that's once again at the age where it's ripe for insect invasions, she explained.

Schoennagel said fire risk increases significantly during the relatively short span when trees are full of dead, red needles.

"You still need extreme drought conditions to coincide with that," she said.

Once the needles fall off. Leaving standing gray snags, the fire risk actually goes down, even below the level of live green trees, she explained. Then it gradually increases again as the trees fall and brush grows.

The key point forest and fire researchers have been trying to make in recent months is that it's an over-simplification to simply say that beetle-killed trees equal overwhelming fire danger, said Ross Wilmore, of the U.S. Forest Service.

"I don't want people to walk away from this thinking we don't have a problem," Wilmore said.

After the presentation, Colorado Timber Industry Association president Carl Spaulding said he found Schoennagel's views to be biased.

"I think it was aimed at finding any way in the world not to utilize the material that's growing out there," Spaulding said. "My feeling is they're not explaining what we can do to manage these results."