Climate Change in the Pacific Region
Pacific Region


Fire Frequency & Intensity in Pacific Northwest Forested Systems

Wildfires will likely increase in all forest types in the coming decades.  Warmer and drier summers leave forests more vulnerable to fire, while wetter winters provide abundant fuel in the form of grasses and shrubs.  Differences in ecosystem-specific correlations between climate and wildfire area burned are highlighted by Littell et al. (2009).  For example, the authors find wildfire occurrence in mountainous ecoprovinces to be highly associated with year-of-fire low precipitation.  Also, snowpack losses and earlier snow melt at lower elevation forests (Mote et al., 2005, Pederson et al., 2013) are increasing fire risk in these areas.

Wildfire frequency in western forests has increased fourfold during the period 1987-2003 as compared to 1970-1986, while the total area burned increased six-fold (Westerling et al., 2006). This study demonstrated that earlier snowmelt dates correspond to increased wildfire frequency.  Trouet et al. (2006) confirm that these increases in area burned are tied to climate conditions despite forest suppression management practices such as thinning.  Prolonged dry and hot periods are generally required for large fires (Gedalof et al., 2005) and future conditions will likely make these periods, and resultant wildfires, more likely.

Other factors include current and past land use, including timber harvest, forest clearing, fire suppression, and fire exclusion through grazing which all affect the amount and structure of fuels in forests. (Vose et al., 2012

fire map

Projected percent increase in burned areas in the West for a 1°C increase in global average temperatures relative to the median area burned during 1950-2003 (National Research Council, 2011)


Learn more and read about the research that provided the information above by checking out the links below:

Allen, C.D.; Savage, M.; Falk, D.A. [et al.]. 2002. Ecological restoration of Southwestern ponderosa pine ecosystems: a broad perspective. Ecological Applications. 12: 1418–1433.

Gedalof, Z., D. L. Peterson, and N. J. Mantua, 2005, Atmospheric, climatic, and ecological controls on extreme wildfire years in the northwestern United States, Ecol. Appl., 15, 154– 174

Littell, J.S., McKenzie D., Peterson D.L., Westerling A.L.  2009b.  Climate and wildfire area burned in western U.S. ecoprovinces, 1916–2003.  Ecological Applications, 19(4), 2009, pp. 1003–1021

Mote, P.W., Hamlet, A.F., Clark M.P., and Lettenmaier, D.P.. 2005. Declining mountain snowpack in western North America. Bulletin of the American Meteorological Society, Vol. 86(1), pp 39-49.

NRC, National Research Council. 2011. Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia. p. 180. Washington, DC: The National Academies Press

Pederson et al. 2013. Regional patterns and proximal causes of the recent snowpack decline in the Rocky Mountains, U.S. Geophysical Research Letters, Vol 40, Issue 8, Published Online 12 MAY 2013, DOI : 10.1002/grl.50424

Trouet, V., A. A. Taylor, A. M. Carleton, and C. M. Skinner. 2006. Fire-climate interactions in forests of the American Pacific coast. Geophysical Research Letters 33:L18704

Vose, James M.; Peterson, David L.; Patel-Weynand, Toral, eds. 2012. Effects of climatic variability and change on forest ecosystems: a comprehensive science synthesis for the U.S. forest sector. Gen. Tech. Rep. PNW-GTR-870. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 265 p.


Last updated: September 3, 2013

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