Multidecadal trends in area burned with high severity in the Selway-Bitterroot Wilderness Area 1880-2012

Abstract

Multidecadal trends in areas burned with high severity shape ecological effects of fires, but most assessments are limited to ∼30 years of satellite data. We analysed the proportion of area burned with high severity, the annual area burned with high severity, the probability areas burned with high severity and also the area reburned (all severities and high burn severity only) over 133 years across 346265ha within the Selway-Bitterroot Wilderness (SBW) Area in Idaho, United States. We used burn severity class inferred from digitised aerial photography (1880-2000) and satellite imagery (1973-2012). Over this long record, the proportion burned with high severity did not increase, despite extensive area burned in recent decades. Much greater area burned with high severity during the Early (1880-1934) and Late (1975-2012) periods than during the Middle period (1935-1974), paralleling trends in area burned. Little area reburned with high severity, and fires in the Early period limited the extent of fires burning decades later in the Late period. Our results suggest that long-term data across large areas provides useful context on recent trends, and that projections for the extent and severity of future fires must consider prior fires and fire management.