Assistant Professor California State University Channel Islands, United States
Megafires, defined as fires with burn areas greater than 100,000 acres (404.7 square kilometers), are partially the result of increasingly short wet seasons coupled with hotter, drier summers, year after year and partially the result of historical forest management decisions. Though megafires historically were rare, they have become increasingly common in recent years. In this study, we demonstrate that beaver-dammed riverscapes (n=1537 beaver dams) have significantly reduced burn severity compared to riverscapes without beaver dams and to areas outside of the riverscape during three megafires that burned in the Rocky Mountain Region in 2020. Additionally, when riverscapes are classified according to their modeled beaver dam capacities (a metric closely linked to riparian habitat quality), beaver-dammed areas had consistently lower burn intensities than those without beaver dams. The impact of beaver damming on burn severity reduction is most pronounced in riverscapes where beaver damming is predicted to be "occasional." Riverscapes in this category also exhibit the largest degree of beaver dam capacity reduction compared to their historic, pre-Euro-American settlement conditions, which suggests they have high potential for restoration via beaver ecosystem engineering. Satellite-derived quantitative normalized difference burn ratio (dNBR) burn severity data from the Cameron Peak (Colorado), East Troublesome (Colorado), and Mullen (Wyoming) fires are included in these analyses, as well as false color mapping and visual inspection of aerial imagery and field photographs as qualitative lines of evidence. Our results indicate that riverscapes with a high degree of landscape manipulation by beavers have robust resistance to burning during wildfire, which may provide valuable secondary benefits in ecosystem health, water quality, and biodiversity post-fire as well.
