Beetle Damage Primes Colorado Forests For Intense Wildfires

Feb 12, 2018

Bark beetle devastation has been an ongoing issue in Colorado's forests for years and remains a concern into 2018. The latest Colorado State Forest Service report says more than 200,000 acres of active infestations were observed in high-elevation spruce-fir forests in Colorado.

Dan West, an entomologist with the service, says drought conditions have contributed to conditions that encourage tree-killing bark beetles to reproduce.

“When you have widespread contiguous forest that are all in a susceptible size class, and growing dense with reduced defenses, it just sets the stage for beetle outbreaks like we’ve seen in the past few years,” he said.

This map depicts the statewide spruce beetle outbreak and the contiguous Engelmann spruce in between the outbreak in Rocky Mountain National Park and the outbreak moving north into the Vail Valley.
Credit Dr. Dan West / Colorado State Forest Service

Those outbreaks lead large swaths of dead, standing trees, greatly increasing the chances of destructive wildfires. In healthy forests, it takes a lot of fuel for a fire to jump to a forest’s canopy, West said.

But "when bark beetles come through ... (fuels) are no longer up in the canopies in those trees,” said West. “The needles have dropped to the forest floor.”

West said problems from massive beetle outbreaks can last for years.

“If it’s just shortly after the bark-beetle outbreak, it’s just needles and small twigs that have dropped to the forest floor,” said West, “but several years after the outbreak, we see the entire tree comes down, and when those wildfires come through, it becomes incredibly hot. So, the intensity if those fires becomes a challenge.”

While funding for clearing out the debris and brush responsible for more intense has historically been hard to come by, some are finding another purpose for beetle-killed trees.

An adult spruce beetle
Credit Dr. Dan West / Colorado State Forest Service

Colorado has an estimated 100 saw mills throughout the state and nearly one-third of them use beetle-killed trees as part of their wood supply. In Grand County, for instance, an estimated 30,000 acres worth of beetle killed trees were sustainably harvested in 2017.

But most of Colorado’s mills are smaller operations, and the state lacks the capacity to fully address the needs of forest management.

Additional highlights from the 2017 Report on the Health of Colorado’s Forests:

  • Spruce beetle was Colorado’s most widespread and damaging forest insect pest for the sixth consecutive year. A total of 206,000 acres with active infestations were observed in high-elevation Engelmann spruce forests.
  • Mature Douglas-fir trees continued to be attacked and killed by Douglas-fir beetle, impacting a total of 14,000 acres in the central and southern portions of the state.
  • Several programs and methods currently are being employed to deal with these bark beetles in the hard-hit Gunnison Basin, including the Western Bark Beetle Program, the use of pheromone treatments to repel beetle attacks, and use of the Good Neighbor Authority to allow state contracting procedures for management efforts on federal lands.