Drive over just about any mountain pass in northwest Colorado and you may notice stands of dead trees with a red tinge. These trees are likely subalpine fir, killed by a combination of the western balsam bark beetle (Dryocoetes confusus) and fungi that cause root decay.
Subalpine fir trees continue to be killed across high-elevation forests. Prolonged drought and dry summers prior to 2022 have weakened defenses in trees, leaving them susceptible to attack by bark beetles. It will take several years of adequate precipitation for subalpine fir to recover their defenses to fend off the western balsam bark beetle, which attacks young as well as mature trees.
Unlike other bark beetles, impacts from the western balsam bark beetle are generally less widespread within a stand of trees. Infestations of the beetle are patchy in a stand – dead trees with a reddish hue intermingle with live green trees. Along with mountain passes, groups of trees killed by western balsam bark beetle are visible near Steamboat Springs in Routt County and Aspen in Pitkin County.
Beetle-killed trees can fall and present hazards for hikers, hunters, bikers and others recreating in forests. Newly infested trees can be removed prior to the adult western balsam bark beetles emerging the following year to infest other trees. However, management is a challenge because of the low value of the wood to offset treatment costs, infestations that are spotty and unpredictable, and remote and steep terrain at high elevations that is difficult to access.
The mountain pine beetle epidemic that killed vast swaths of lodgepole pine forests in the early to mid-2000s in northwest Colorado subsided many years ago. Its impact, however, remains and presents one of the most concerning forest health issues in this part of the state.
Standing dead, gray trees are falling at an increasing rate, creating a labyrinth within emerging grasses, shrubs and young trees growing through the maze of fallen lodgepole pine. This has created a large amount of surface fuels in forests, which can contribute to extreme wildfire behavior and rapid growth of fires. The record-breaking East Troublesome and Cameron Peak wildfires in 2020 exemplify how this fuel arrangement can lead to massive fires under very dry and windy conditions.
This accumulation of down beetle-killed trees results in a myriad of concerns:
This combination of mountain pine beetle impacts and wildfires may ultimately alter the trajectory of these forests. Once-treed areas may have difficulty regenerating a new, healthier forest.
The Colorado State Forest Service continues to remove fuels from forests in targeted areas, especially around homes, communities and watersheds. The forest products industry has been a crucial partner in offsetting costs for these treatments. In addition, partnerships among local, state, federal and private entities remain critical to leveraging resources and addressing the challenges these fuel conditions create at a scale equal to the problem.
Douglas-fir beetle (Dendroctonus pseudotsugae) continues to cause significant mortality of Douglas-fir trees in parts of northwest Colorado. This beetle, a close relative of spruce beetle and mountain pine beetle, is a native insect that inhabits mature Douglas-fir forests across most of the West. Levels of tree mortality from Douglas-fir beetle vary widely and occur in pockets, from scattered trees in some areas to almost the total loss of mature stands in others.
Since 2020, drought conditions have stressed trees and left them vulnerable to attack by the Douglas-fir beetle. The beetle heavily affected forests in Eagle, Garfield, Mesa and Pitkin counties last year and has increased in activity in the Roaring Fork Valley since the Lake Christine Fire in 2018.
In an attempt to slow the spread and impact of Douglas-fir mortality, the Colorado State Forest Service teamed with the City of Aspen and its partners to deploy pheromones packets on Ute and Shadow mountains. The partners plan to continue this treatment until beetle populations decline and tree defenses fortify.
A $1.23 million donation kickstarted fundraising efforts to transform the Michigan River Camp at the Colorado State Forest into a facility that offers place-based learning, training and research.
Working with many partners and across boundaries on nearly 1800 acres, foresters in the Steamboat Springs Field Office have managed critical work that’s reduced wildfire risk and benefited the local economy.
Staff at the Colorado State Forest pooled funding to carry out a crucial forest health project on about 600 acres of State Trust Lands in southeast Jackson County.
