Smokey the Beaver: beaver‐dammed riparian corridors stay green during wildfire throughout the western United States

Abstract

Beaver dams are gaining popularity as a low-tech, low-cost strategy to build climate resiliency at the landscape scale. They slow and store water that can be accessed by riparian vegetation during dry periods, effectively protecting riparian ecosystems from droughts. Whether or not this protection extends to wildfire has been discussed anecdotally but has not been examined in a scientific context. We used remotely sensed Normalized Difference Vegetation Index (NDVI) data to compare riparian vegetation greenness in areas with and without beaver damming during wildfire. We include data from five large wildfires of varying burn severity and dominant landcover settings in the western United States in our analysis. We found that beaver-dammed riparian corridors are relatively unaffected by wildfire when compared to similar riparian corridors without beaver damming. On average, the decrease in NDVI during fire in areas without beaver is 3.05 times as large as it is in areas with beaver. However, plant greenness rebounded in the year after wildfire regardless of beaver activity. Thus, we conclude that, while beaver activity does not necessarily play a role in riparian vegetation post-fire resilience, it does play a significant role in riparian vegetation fire resistance and refugia creation.

Beaver dams attenuate flow: A multi‐site study

“…This study focuses on high flow periods, but it is worth noting that reduced flashiness observed supports research indicating the slowed release of water from leaky dams may maintain or elevate stream baseflows (Nyssen et al, 2011) during dry periods (Majerova et al, 2015; Puttock et al, 2017; Woo & Waddington, 1990). There is a need for further research into baseflow maintenance, with an increase in hydrological extremes predicted globally (Dadson et al, 2017; Larsen et al, 2009; Romanowicz et al, 2016) both attenuating stormflow and maintaining flow and wetness during drought periods (Fairfax & Small, 2018; Gibson et al, 2015) or even fire episodes (Fairfax & Whittle, 2020) which could have major ecological and societal benefits.…”

Rediscovering, Reevaluating, and Restoring Lost River-Wetland Corridors

“…In a fully functional river-wetland corridor, this intrinsic, geomorphic resilience to disturbance is further enhanced by riverine biota. Beaver modifications of the river corridor increase resilience to drought (Hood and Bayley, 2008) and wildfire (Fairfax and Whittle, 2020). The dense vegetation of river-wetland corridors can enhance the resistance of these systems to flood-induced erosion and deposition (Heffernan, 2008).…”

“…Resilience is the persistence of relationships within a system and is a measure of the ability of the system to absorb changes of state and driving variables (Holling, 1973). River-wetland corridors are generally more resistant to drought and wildfire because of the elevated water table and relative abundance of standing water (e.g., Hood and Bayley, 2008;Fairfax and Whittle, 2020). Sediment pulses that can severely damage dysfunctional channels in the aftermath of wildfire are instead distributed and attenuated across functional river-wetland corridors, resulting in less significant impacts.…”

Beaver: Nature's ecosystem engineers

“…This in turn can increase the duration of the rising limb of the flood hydrograph which can reduce the peak discharge of floods (Burns & McDonnell, 1998; Green & Westbrook, 2009; Nyssen, Pontzeele, & Billi, 2011). Additionally, water stored in beaver ponds is released slowly as the porous dams gently leak both during and following rainfall, elevating stream base flows even during prolonged dry periods (Majerova, Neilson, Schmadel, Wheaton, & Snow, 2015; Puttock et al, 2017; Woo & Waddington, 1990), increasing environmental resilience to risks including drought and fire (Fairfax & Whittle, 2020).…”