WWETAC Projects

Project Title: Climate change and forest diseases in the West—An information synthesis

Principal Investigator: Susan Frankel, Pacific Southwest Research Station, Albany, CA


Collaborators: Charles G. Terry Shaw , Western  Wildland Environmental Threat Assessment Center, (Emeritus) Pacific Northwest Research Station, Prineville, OR;  Erica Fleishman, University of California, Davis;John T Kliejunas, (Retired), USDA Forest Service, Pacific Southwest Region, Forest Health Protection;  Brian W. Geils, USDA Forest Service, Rocky Mountain Research Station;   Jessie Micales Glaeser, USDA Forest Service, Forest Product Laboratory;  Ellen Michaels Goheen, USDA Forest Service, Pacific Northwest Region, Forest Health Protection;  Paul Hennon, USDA Forest Service, Pacific Northwest Research Station;  Harry Kope, B.C. Ministry of Forests; Jeff  Stone, Oregon State University; Rona Sturrock, Canadian Forest Service, Pacific Forestry Centre.

Key Issues/Problems Addressed:

Predicted climate effects on forest diseases in the Western United States are needed to inform managers, decision makers, scientists, and communities.

Setting and Approach:

Information concerning relevant climate, climate change, and forest diseases in the Western United States was compiled. The document summarizes what is known about environmental influence (primarily temperature and moisture) on forest fungi, bacteria, nematodes, other microbes, and extreme abiotic stresses. The following concepts were explored for their influence on forest pathogens: (1) phenological change (such as movement west of Spruce Budworm), (2) habitat changes—increased tree mortality in a specific tree size and species, favoring decay organisms, (3) climate changes that favor a disease agent ( i.e., El Nino and Sudden Oak Death, Phytopthora ramorum ), (4) warmer temperatures eliminating freezing conditions or snow pack (i.e., Alaska Yellow Cedar decline), and (5) weather extremes and pathogens—hurricane winds spreading the Citrus Canker pathogen.

Key findings:

  • Climate change will affect the geographical distribution of plant diseases, the losses they cause, and the efficacy of disease management strategies.
  • Climate change will alter the epidemiology of plant diseases.
  • Changes in interactions between biotic diseases and abiotic stressors may represent the most substantial effect of climate change on plant diseases.
  • If climate warms, overwintering survival of pathogens and disease severity are likely to increase.
  • Climate change will lead to reductions in tree health and will improve conditions for some highly damaging pathogens.
  • Climate change may facilitate invasion by new nonnative pathogens and new epidemics may occur as a result.


Management objectives for forest ecosystems as climate changes will require multiple approaches, including models, formal assessments, distributed learning networks, and adaptation policies that are responsive to a wide variety of environmental circumstances.


Sturrock, R. N., Frankel, S. J., Brown, A. V., Hennon, P. E., Kliejunas, J. T., Lewis, K. J., Worrall, J. J. and Woods, A. J. (2011), Climate change and forest diseases. Plant Pathology, 60: 133–149. doi: 10.1111/j.1365-3059.2010.02406.x (PDF, 487 KB)

Kliejunas, John T. 2011. A risk assessment of climate change and the impact of forest diseases on forest ecosystems in the Western United States and Canada. Gen. Tech. Rep. PSW-GTR-236. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 70 p. (PDF, 2.75 MB)

Kliejunas, John T. and 9 others. 2009. Review of literature on climate change and forest diseases of western North America.Gen. Tech. Rep. PSW-GTR-225.USDA Forest Service, Pacific Southwest Research Station, Albany, CA 54p. (PDF, 3.53 MB)

WWETAC Project ID: FY07TS32