Native Bark Beetles in the Western United States: Who, Where, and Why

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1 Native Bark Beetles in the Western United States: Who, Where, and Why Barbara J. Bentz Rocky Mountain Research Station USDA Forest Service Logan, UT Photo Ryan Bracewell Forest and Woodland Ecosystem Research

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4 Native Western US Bark Beetle Species That Can Cause Landscape-Wide Tree Mortality Mountain pine beetle Dendroctonus ponderosae Western pine beetle D. brevicomis Spruce beetle D. rufipennis Douglas fir beetle D. pseudotsugae Roundheaded pine beetle D. adjunctus Jeffrey pine beetle D. jeffreyi Southern pine beetle D. frontalis Arizona fivespined ips Ips lecontei Pinyon ips Ips confusus Pine engraver Ips pini Western balsam bark beetle Droycoetes confusus

5 1925 Photo JM Miller Mountain pine beetle-killed lodgepole pine in Yosemite National Park, CA Photo M Furniss

6 Native bark beetles have affected > 63 million acres in the western US over the past decade (USDA Forest Health Protection) High elevation ecosystems

7 Bark Beetle-Caused Tree Mortality in 13 Western US States: 1999 to Alaska 3 3. Idaho 3 3. Montana 3 3. South Dakota Washington 3 3. Nevada 3 3. Wyoming Oregon 3 3. Utah 3 3. Colorado California 3 3. Arizona 3 3. New Mexico Data source: USDA Forest Service, Forest Health Protection, Aerial Detection Surveys

8 Whitebark pine Pinus albicaulis Cronartium ribicola White pine blister rust Photo Wally MacFarlane Mountain pine beetle Native Exotic Photo Diana Tomback Photo Diana Tomback Whitebark pine is currently being considered for Threatened or Endangered Status, USFWS

9 Multiple factors are influencing recent mountain pine beetle outbreak dynamics: Legacies of past management created large expanses of susceptible-aged & homogenous forests. lodgepole pine

10 Multiple factors are influencing recent mountain pine beetle outbreak dynamics: Legacies of past management created large expanses of susceptible-aged & homogenous forests. lodgepole pine Environmental Changes - precipitation temperature Source:

11 Thresholds and positive feedback processes at multiple scales contribute to the eruptive, outbreak nature of aggressive bark beetle populations. Raffa et al. 28, Bioscience

12 Future Predictions Probability of Survival Mountain pine beetle Cold Tolerance Normals, CRCM v IPPC A2 scenario Régnière & St-Amant. 27 Bentz et al. 21

13 Probability of Survival Mountain pine Beetle Cold Tolerance 21-23

14 Probability of Survival Mountain pine Beetle Cold Tolerance

15 What can be done? Tree protection in high value recreation areas and near homes is possible with: insecticides semiochemicals verbenone Bark beetle-killed tree removal in recreation areas and near power lines. Senator Mark Udall

16 What can be done? (cont.) Optimal management strategies for a forest and a wildland urban interface are not the same. Optimal management strategies will differ across ecosystems and geographic locations. Reducing tree mortality in forests after a bark beetle outbreak has started is not feasible. Silvicultural manipulations can be used to reduce susceptibility of some forest types to bark beetle attack prior to outbreak initiation. Create a diverse forest landscape through modifications to species and age classes at a regional scale. Forest management strategies should incorporate projections of climate-change on both forests and beetle population dynamics.

17 Do bark beetle outbreaks influence other forest disturbances such as wildfire? Research suggests there is NOT a direct correlation between bark beetle-caused tree mortality and large wildfire. The relationship is dynamic and an ignition source and fire weather are important drivers. Using Landsat satellite data, University of Wisconsin forest ecologist Phil Townsend and his team are discovering that pine beetle damage appears not to have a significant impact in the risk of large fires. In fact, it might even reduce fire risk in some instances. Source: www. nasa.gov

18 FIRE HAZARD high bark beetle outbreak forest dieback Surface Fire Canopy Fire low Live, water-stressed conifer forest Extensive tree mortality, dead needles still on trees Dead needles drop, Fine surface fuels, Surface fuels drier Dead trees start to fall. Herb and shrub and tree re-growth, Coarse woody surface fuels TIME From: Bentz et al. 21