HISTORIC AND FUTURE WILDFIRES IN THE SOUTHERN ROCKIES ECOREGION, USA

Wildfires play a necessary but formative role in the processes that have created the Southern Rockies Ecoregion (SRE). The threat of wildfires is influenced mainly by precipitation and temperature, which control fuel growth and fuel moisture. Climate change in the SRE has already been shown to increase temperatures, bringing warmer springs and summers with earlier spring runoff and longer fire seasons. It is critical to quantify likely changes in burned areas because increasing wildfire extent and intensity would affect safety, livelihoods, and landscapes in multiple ways. We summarized the historical wildfire record in the National Forests of the SRE from 1930 to 2006 and showed an order of magnitude increase in the annual number of fires recorded over the full time period and in the occurrence of large fires since 1970. Using temperature and precipitation variables, our model of percent burned area in the SRE accounts for 48% of the variability over the period 1970-2006. Applications of this model with data from two downscaled GCMs, for IPCC SRES climate scenarios A2 and B1, and for the time periods 2010 to 2040 and 2041 to 2070 generally show increasing trends in burned areas, with the most severe increases occurring during the second time period. The results provide important information to natural resource managers and planners to assist in wildfire management, land use planning, and water resource management.