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Pine Beetle Suppression: Does Science Support Current Policy?

Conclusion: Gutting environmental laws to speed logging in national forests experiencing bark beetle outbreaks is not supported by scientific evidence. Virtual clearcutting removes nearly all beetle resistant trees making the forest more susceptible to future outbreaks and the impacts of climate disruption.

Key quotes:

  • There is a disturbing dearth of rigorous replicated empirical studies assessing the effects of various management strategies, particularly timber harvest treatments, for bark beetle outbreak suppression.

  • Tom Tidwell, Chief of the Forest Service, criticized recent bipartisan legislation because it would "shortchange the environmental review process, cut out public engagement and collaboration...and override roadless protections.

  • From a manager's perspective, outbreaks are often perceived as a symptom of poor "forest health", while ecologists more often view outbreaks as natural ecological processes integral to the maintenance and resilience of the forest.

  • ponderosa pines in the thinned stands exhibited lower water stress but also produced less resin. This, along with the thicker phloem (greater food resources) found in trees in thinned stands, indicates they might be not only more susceptible to attack but also a more productive resource for beetles.

  • While widely recommended, the efficacy of this treatment (thinning) is unknown; there are no published studies on its effects on bark beetles.

  • Many studies assessing the efficacy of thinning have been conducted under non-outbreak conditions. Their results do not reflect how stands perform during an outbreak.

  • [mountain pine beetle] act as a natural thinning agent and seldom removes all mature trees during outbreaks

  • beetles often leave sufficient numbers of large diameter trees to maintain a dominant overstory of pine. Beetles also leave substantial amounts of advanced regeneration to replace the mature trees that are killed.

  • when humans thin forests, trees are removed according to size, species, and density, without consideration of genetics. Thus, trees best adapted to surviving beetle outbreaks are as likely to be removed as those that are not.

  • Agencies often do not have strong incentives to conduct long-term monitoring: Monitoring is costly; external and internal political pressures focus on short time frames; and monitoring may produce information that conflicts with agency goals or missions.

  • there is significant uncertainty about whether the most commonly used beetle timber harvest treatments are, indeed, effective.

  • our position is that weakening or eliminating environmental laws to allow more beetle timber harvest treatments is the wrong choice for advancing forest health in the United States . . . we believe that the current structure of thoughtful, detailed environmental review for these projects is, in general, appropriate.

  • the push to "do something," uncertainty, and political pressures might lead us to act to respond to climate change before we understand the consequences of what we are doing, in the end producing more harm than good.


Lead author Diana L. Six is professor of Forest Entomology and Pathology at the University of Montana, Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT.

Here's the full article:

      Management for Mountain Pine Beetle Outbreak Suppression: Does Relevant Science Support Current Policy?