Beaver-Modified Riverscapes Resist Burning During Megafires

Year: 2023
Presenter/s: Emily Fairfax
Symposium Session: 2023 - 08 - Restoration as Risk Reduction: Wildfire
Topics covered: beavers, california, climate change, colorado, idaho, mountain west, risk and resilience, and wildfire


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. Though megafires historically were rare, they have become increasingly common in recent years. These fires pose unique challenges – they have exceptionally fast rates of spread, generate their own self-sustaining weather systems, and can easily cause secondary ignitions in the surrounding landscape via ember spotting and lightning strikes from pyrocumulus clouds. This culminates in an environment where the fire perimeter expands rapidly, posing significant risks to both humans and ecosystems. Large rivers already are utilized as fire breaks in small to medium-sized fires – fire management plans take advantage of the fact that water doesn’t easily burn. Riverscapes, however, include far more than just the river channel itself – they include the floodplains, the wetlands, the wet meadows, the side channels, the subsurface hyporheic zone, and the shallow groundwater systems historically created and maintained by widespread native beaver activity across most river valley bottoms. Beavers, and their innate ecosystem engineering behaviors, are uniquely capable of restoring and rewetting riverscapes even under highly modified and simplified modern stream and river conditions. In this study, we demonstrate that beaver-dammed riverscapes have significantly reduced burn severity compared to both riverscapes without beaver and to the landscape as a whole. Satellite-derived quantitative dNBR burn severity data are included in these analyses, as well as false color mapping and visual inspection of aerial imagery and on-ground 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.