Rethinking the focus on forest fires in federal wildland fire management: Landscape patterns and trends of non-forest and forest burned area

For most of the 20th century and beyond, national wildland fire policies concerning fire suppression and fuels management have primarily focused on forested lands. Using summary statistics and landscape metrics, wildfire spatial patterns and trends for non-forest and forest burned area over the past two decades were examined across the U.S, and federal agency jurisdictions. This study found that wildfires burned more area of non-forest lands than forest lands at the scale of the conterminous and western U.S. and the Department of Interior (DOI). In an agency comparison, 74% of DOI burned area occurred on non-forest lands and 78% of U.S. Forest Service burned area occurred on forested lands. Landscape metrics revealed key differences between forest and non-forest fire patterns and trends in total burned area, burned patch size, distribution, and aggregation over time across the western U.S. Opposite fire patterns emerged between non-forest and forest burns when analyzed at the scale of federal agency jurisdictions. In addition, a fire regime departure analysis comparing current large fire probability with historic fire trends identified certain vegetation types and locations experiencing more fire than historically. These patterns were especially pronounced for cold desert shrublands, such as sagebrush where increases in annual area burned, and fire frequency, size, and juxtaposition have resulted in substantial losses over a twenty-year period. The emerging non-forest fire patterns are primarily due to the rapid expansion of non-native invasive grasses that increase fuel connectivity and fire spread. These invasions promote uncharacteristic frequent fire and loss of native ecosystems at large-scales, accelerating the need to place greater focus on managing invasive species in wildland fire management. Results can be used to inform wildfire management and policy aimed at reducing uncharacteristic wildfire processes and patterns for both non-forest and forest ecosystems as well as identify differing management strategies needed to address the unique wildfire issues each federal agency faces.