Climate and snowpack interactions regulate annual area burned across western North America

KITZBERGER, T.; FALK, D.; SWETNAM, T.W.; WESTERLING, T.L.

Santa Fe, Nueva Méjico

Conferencia; Southwest Fire Ecology Conference; 2012

Association for Fire Ecology

Warming temperatures have been identified as triggering factors for increased fire activity over certain regions of North America but a more complete geographic assessment of climate-modern fire influences is needed in order to make more informed predictions of future fire activity under climate change scenarios. Snowpack duration can influence fire activity and area burned directly by regulating the provision of water to soils and plants; conversely, earlier snowpack melt may simply manifest drier and warmer springs which desiccate fuels irrespective of snowpack. We analyzed area burned data for the western US and most of Canada for 1972-2004, and compared these with seasonal temperatures, precipitation, and snowpack duration. A strong increasing trend exists in annual area burned over the 34-year period of record. Snow cover duration has declined over most of North America during this period, particularly in the west. Seasonal temperatures are higher in all seasons analyzed (winter, spring, summer) across most of the continent. Trends in seasonal precipitation are more geographically variable. We used Path Analysis to segregate direct and indirect influences of seasonal temperature and precipitation, and snowpack duration on annual area burned in 2.5 degree grid cells. Spring temperature has an important effect on snow cover duration at high latitudes across boreal North America, whereas winter temperature and precipitation affects snow cover duration at mid latitudes and lower altitudes. We used the IPCC Fourth Assessment SRES Ensemble Scenario A1B to project future values of key drivers of snowpack and annual area burned to AD 2040.