Review of the Forest Service Perspective: The Bark Beetle Outbreak in Northern Colorado and Southern Wyoming

摘要

A mountain pine beetle outbreak in three national forests in the Rocky Mountain Region (Region 2) of the U.S. Forest Service--the Arapaho-Roosevelt, Medicine Bow-Routt and White River--was initially detected in 1996. By 2010 it had spread to about four million acres. This report examines the ecological conditions and historical land use that contributed to the outbreak, management response to the outbreak, suggested new and extended authorities for addressing the outbreak, and what we might expect as we look forward to the new forest. Bark beetles are a natural part of forest ecosystems throughout the world. However, bark beetles are killing trees in larger numbers, at faster rates, over longer time periods, and over larger areas compared to outbreaks recorded over the past century. Moreover, outbreaks are occurring in multiple forest types. Reasons for these changes are unclear, but they include a changing climate affecting both insect and host; previous management practices such as selective timber harvesting and wildfire suppression in some forest types; a maturing forest due in part to changing disturbance patterns; and prolonged drought, which can stress trees and make them more vulnerable to insect attacks.