Historic and future extent of wildfires in the Southern Rockies Ecoregion, USA

Abstract

Wildfires play a formative role in the processes that have created the ecosystems of the Southern Rockies Ecoregion (SRE). The extent of wildfires is influenced mainly by precipitation and temperature, which control biomass growth and fuel moisture. Forecasts of climate change in the SRE show an increase in temperatures, bringing warmer springs with earlier runoff and longer fire seasons. Increasing wildfire extent and intensity would affect human safety, livelihoods, and landscapes. Our summary of historical wildfire records from the national forests of the SRE from 1930 to 2006 revealed an order of magnitude increase in the annual number of fires recorded over the full time period and in the number of large fires since 1970. We developed a model of percent burned area in the SRE for the period 1970–2006 using temperature and precipitation variables (R2=0.51, p=1.7E-05). We applied this model to predict percent burned area using data from two downscaled global circulation models (GCMs), for the Intergovernmental Panel on Climate Change Special Report Emissions Scenarios A2 (projects high increases in temperature) and B1 (projects lower temperature increases), for the time period 2010–2070. The results showed increasing trends in median burned areas for all scenarios and GCM combinations with higher increases for the B1 scenario. The results suggest that precipitation increases could at least partially compensate for the effect of temperature increases on burned area but the strength of this ameliorating effect of precipitation will remain uncertain until the GCMs are further developed.