There are many pests, blights and diseases forest rangers monitor, but locally, spruce bark beetle has risen to the top of the list, munching through the landscape at an alarming rate.
U.S. Forest Service officials are evaluating potential strategies to combat the problem and may employ logging, reforestation and managed burning.
Kara Chadwick, San Juan National Forest supervisor, said the agency is working on an overall strategy to manage the infestation.
From 1996 through 2013, the beetle infested 183,000 acres in the San Juan National Forest, according to the most recent data available. In 2013 alone, the beetle invaded 53,000 acres, the biggest gain it has made in the forest in a single year.
Some of the most visible damage has been across Wolf Creek Pass and areas northeast and northwest of Vallecito Reservoir. Other areas have been identified through aerial monitoring. The Forest Service will be doing more on-the-ground surveys in the spring and summer, said Steve Hartvigsen, a supervisory forester.
The naturally occurring beetles live in Engelmann spruce. The epidemic levels have been fed by windy spring weather and drought. Then major snowstorms in 2005 and 2007 forced many old spruce to fall, providing the beetles with plenty of habitat. Dry subsequent years helped the beetles flourish in standing trees.
“All these conditions have added up to some very happy, successful spruce beetles,” Hartvigsen said.
Fighting the infestation
Proactively thinning the trees by logging can create an opportunity for young trees to sprout and create a stand of trees that are less susceptible to the beetles, he said. This kind of tree harvest creates a mosaic of old and new growth.
Managing fires lit by natural sources is part of a national effort to manage forests. However, managing fires in a spruce forest can be difficult because they are naturally more moist and cooler than the ponderosa pine forest at the lower elevations. When the spruce forest is dry enough to burn naturally, it is likely the ponderosa pine forest will be dangerously dry, Hartvigsen said.
However, naturally lit fires that are allowed to burn in the right location can be managed to protect human structures and even reduce smoke, he said.
San Juan National Forest officials plan to hold public meetings in February or March to talk about plans to address the problem.
“We’ll look at all the tools available,” Chadwick said.
An infested West
Beetle infestations have been a challenge for forests all across the Western U.S. after about 135 years of fire exclusion. During this time fires didn’t burn naturally because of human activity and about 20 years of unusually wet weather. This has led to forests populated by older trees and more conifers instead of aspens.
“Add all these factors with now a warming climate that’s being recognized – all that has led to higher incidents of bark beetles,” Hartvigsen said.
As a result, officials in some areas have called on sawmills and other wood consumers to help manage the problem. Starting in 1998, Grand County’s mountain pine-beetle problem began to grow exponentially, County Manager Lurline Underbrink-Curran said. The landscape, home to Granby, changed from green to red to gray as the trees were infested and died.
“We had the fastest growth and the most noticeable growth in that infestation compared to the other countries around us,” she said.
In the early days, the county and private landowners brought in loggers to combat the problem, and now, new growth is visible in those areas.
The epidemic levels subsided in 2008, leaving about 200,000 acres of impacted forest just in the Sulphur Ranger District.
“We’re absolutely still in the process of dealing with the aftermath,” District Ranger Craig Magwire said.
Selling timber is one of the most cost-effective ways to clear what could become fuel for a fire, he said.
After the housing-market crash, demand for wood from these infested forests is coming back strong, said Nancy Fishering, Colorado programs manager for the Intermountain Forest Association.
There now is demand from biomass power plants and wood-pellet mills that can use much lower-grade wood.
mshinn@durangoherald.com