April 10, 2002
Five years after a fierce storm caused a massive “blowdown” of four million trees in Routt National Forest in northern Colorado, the U.S. Forest Service has decided on action to combat a spruce bark beetle infestation resulting from the storm. The situation has been compounded by a separate and unrelated occurrence — a mountain pine beetle epidemic.
The two epidemics, according to the USFS, threaten to kill the majority of mature spruce and lodgepole pine trees in northern Colorado and southern Wyoming.
The USFS released a Bark Beetle Final Environmental Impact Statement describing five alternatives to address the beetle epidemic. After considering the bark beetle analysis and public input, Routt National Forest Supervisor Mary Peterson selected portions of Alternative D of the EIS to be implemented, and signed three Records of Decision, calling for:
- Watershed improvement projects in several drainages, and protective spraying to prevent infestations on the Steamboat Ski Area, campgrounds, scenic corridors and some urban areas before beetles arrive.
- Suppression activities within a 259,200-acre suppression zone, including burning or peeling infested trees to kill beetles before they can leave those trees and infest other nearby trees. In addition, the USFS will use trap trees and pheromones to attract beetles to trees which will later be peeled or burned to kill beetles, or remove infested trees from the forest as salvage logs.
- Preventive thinning of approximately 5,750 acres of spruce/lodgepole pine stands in the Coulton Creek, Floyd Peak and Red Creek areas to make the stands more vigorous and more resistant to beetle attacks.
“It’s uncertain exactly how the epidemics will progress, so we’re going to do monitoring every year to determine what the beetles are doing, and how our actions are effecting the beetles and the forest. We will use the results of the annual monitoring to determine future actions, and if additional analysis is needed,” Peterson said.
“We can’t prevent beetle epidemics, and we’re not trying to stop them,” she said. “We’re trying to limit impacts of the epidemics in a few high-value areas,” Peterson added.
According to the EIS Executive Summary, the adopted actions are meant to reduce the number of trees killed by bark beetles “where resource, social, or economic values are threatened as the epidemic continues.” Among the objectives are to limit the spread of an epidemic to private lands and maintain “healthy and aesthetically pleasing stands of trees” at Steamboat Ski Area.
The USFS is not addressing salvage and reforestation at this time, but expects to address the issues at a later date.
The spruce beetle is native to North America and has evolved with spruce trees over thousands of years. It is always present in small numbers in healthy forests. Beetles play a role in the natural recycling system of spruce forests as the primary, initial decayers of dead trees. When abundant host trees are present, such as after a blowdown, spruce beetle populations can become so large that they exhaust that food supply and move on to inhabit and kill live trees.
Beetles can kill live trees by breeding and laying eggs in the phloem (or vascular tissue) of trees, which conveys water and food to the tree. When beetle eggs hatch, the larvae feed in the phloem, thus cutting off food and water and effectively killing the tree.
The spruce beetle generally has a two-year life cycle. Adult beetles, about the size of a grain of rice, mate and lay eggs under the bark of trees. When the eggs hatch, they begin to feed in the first year. During the second year, the larvae become pupae, then “callow” adults, which overwinter and emerge the second spring to mate.
The Routt Divide blowdown provided beetles with huge amounts of breeding material and attracted spruce beetles from the surrounding forest. Populations of beetles were expected to become so large that they would need to move to live spruce trees for food.
Northwestern Colorado is also experiencing an increase in mountain pine beetles, which is part of a natural cycle of the insect, occurring every 20-30 years. Almost identical to the spruce beetle in appearance, the mountain pine beetle lives most of its life under the bark of mature lodgepole or ponderosa pine trees, which grow at lower elevations. It has the potential to kill large numbers of trees.
Together, the beetle epidemics could not only leave thousands of dead trees in the Routt National Forest, but also pose an extreme fire risk as the amount of fuel (or dead trees) increases
The Bark Beetle Analysis Final Impact Statement, an executive summary, and the Records of Decision can be found at www.fs.fed.us/r2/mbr.