Assessment and Response to Bark Beetle Outbreaks in the Rocky Mountain Area

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Bark beetles act as “agents of change” within the conifer forests of the Rocky Mountain area. They play a critical role in the development, senescence, and rebirth of Western forests. Bark beetle-caused tree mortality can be extensive, covering thousands of acres. This report is the Forest Service response to a Congressional direction in the FY2000 Interior and Related Agencies Appropriations Act asking for the causes, effects, and management options for native bark beetle outbreaks in the Rocky Mountain area. This report focuses on three principal species: mountain pine beetle, spruce beetle, and Douglas-fir beetle. Forest management practices subsequent to Euro- American colonization have significantly altered forest structure and diversity. Many forested landscapes in the Rocky Mountain area are composed of overstocked stands with decreased biodiversity. As a result, larger, more contiguous landscapes in these areas have become simultaneously susceptible to bark beetle outbreaks. A combination of biotic and abiotic factors often must occur before an outbreak develops. In some ecosystems (such as lodgepole pine), beetle outbreaks and subsequent fires are often stand-replacing events critical to maintaining the species over much of its distribution. Bark beetle-caused tree mortality also provides important habitat for some species of wildlife, provides coarse woody debris to streams, and contributes to nutrient recycling. Negative effects on wildlife include loss of hiding cover and older tree habitat crucial for some species of threatened and endangered wildlife. Outbreaks can severely affect resource objectives, particularly in high-value recreation areas, watersheds, and wildland/urban interface landscapes, and impact timber production sites. Effective management strategies for direct and indirect control of bark beetle populations include prevention, suppression, and restoration. Prevention strategies are designed to change forest conditions that render them susceptible to bark beetle. Suppression strategies are designed to suppress or control existing populations of the insect. Restoration strategies reestablish ecosystem’s ecological integrity to a degree to which the ecosystem’s components and their relationships are present, functioning, and capable of self-renewal. All three strategies are needed to formulate an effective bark beetle management policy. Formulation of an effective management strategy faces significant challenges resulting from conflicting objectives when combining ecological principles and social constraints. The Rocky Mountain area requires a comprehensive strategy that addresses multiple land-use objectives, specific bark beetle species, and site conditions. To develop this strategy and implement these activities, we must address a myriad of needs, including public education, research, technology transfer, early detection, and monitoring.


This item was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.