This study examines the positive effects of beaver damming on the resistance of landscapes to wildfire damage. The authors find that in riparian corridors (areas along rivers), the presence of beavers and their dams can create refuges that withstand blazes that consume surrounding vegetation.
Beavers play an important role in wetland habitats and are known as ecosystem engineers for the way they can shape landscapes with their activities. Beaver dams slow down water moving across a landscape, holding it in place for longer and allowing water to infiltrate into the soil, which raises water tables.
The combination of building flow obstructions (dams), accumulating water (ponds), and spreading that water out in the landscape (channels) gives beavers the unique potential to modulate environmental extremes such as flood and drought. When it comes to water, beavers slow it, spread it, and store it.
Due to the fact that beaver channels and dams spread water out in the landscape and store it broadly in adjacent soils, the vegetation near beaver ponds doesn’t experience as much reduced water availability during drought. Drought-stricken vegetation burns more easily than lush, green vegetation, so it follows that the vegetation around beaver ponds would be more difficult to burn than vegetation around undammed creeks [Fairfax and Whittle 2020: 1].
Fairfax and Whittle observed the effects of beaver dams on preventing fire spread to the areas where they had built dams, examples of which are shown in satellite imagery below.
The authors quantify the effects of beaver activity in fireproofing areas by examining the Normalized Difference Vegetation Index (NDVI) observed in satellite imagery before, during, and after wildfire years in the American West. They found that while vegetation is able to reestablish itself a year after fire damage regardless of beaver activity due to its own resilience to fire, areas in beaver dammed zones maintained vegetation even during wildfires, demonstrating actual resistance to blazes, not just the ability to recover after damage. They note how vital this is for those ecosystems and the life within them.
These ribbons of fire-resistant riparian corridor may be particularly important for species that are unable to physically escape wildfire. They can provide temporary habitat for fish, amphibians, reptiles, small mammals, wild and domestic ungulates, and birds that are unable to outrun/outfly the spread of flames. While we found that beaver activity does play a significant role in maintaining vegetation greenness during wildfires, it does not appear to play a significant role in the ability for a riparian corridor to rebound in the year following fire. Riparian vegetation NDVI rebounded in the year following the fire regardless of proximity to beaver activity. Thus, we would describe beaver activity as creating refugia during wildfire, but not necessarily changing the long-term landscape outcomes [Fairfax and Whittle 2020: 7].
The survival of wildlife is crucial to these ecosystems, and beaver activity uniquely contributes to the creation of refuge areas that resist burning and can provide shelter for animals during these destructive events. The authors conclude,
As it stands today, wetland habitat is very limited and beavers can create and maintain wetland habitat that persists through flood, drought, and, as we have shown in this study, fire. This has immediate relevance to scientists and practitioners across North America and Eurasia, particularly in places with increasing wildfire risk and existing or planned beaver populations. Perhaps instead of relying solely on human engineering and management to create and maintain fire-resistant landscape patches, we could benefit from beavers’ ecosystem engineering to achieve the same goals at a lower cost [Fairfax and Whittle 2020: 7].
Fairfax, Emily & Whittle, Andrew, 2020, Smokey the Beaver: beaver‐dammed riparian corridors stay green during wildfire throughout the western United States, Ecological Applications 30(8), https://doi.org/10.1002/eap.2225.