https://doi.org/10.1002/eap.2225 Corresponding Editor: Nancy F. Glenn.
Ecological Applications, Volume 30, Issue 8
“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.
“Beavers are native to North America (Castor canadensis) and to Eurasia (Castor fiber; Naiman et al. 1988, Wróbel 2020). They occupy a variety of landscapes, including mountain streams, lowland valleys, coastal estuaries, deserts, arctic tundra, and temperate forests. (Naiman et al. 1988, Leidholt‐Bruner et al. 1992, Pilliod et al. 2017, Tape et al. 2018). Beavers are well known ecosystems engineers; they build channel‐spanning dams from wood, stone, and mud that ultimately create the broad ponds and wetlands that beavers thrive in (Hammerson 1994). Beavers also excavate mud from the pond bottom and dig channels (also referred to as canals) radiating from the pond out into the surrounding landscape, which fill with water and increase their area of influence (Gurnell 1998). 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 (Hood and Bayley 2008, Pilliod et al. 2017, Fairfax and Small 2018, Westbrook et al. 2020). 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 (Fig. 1, top), the vegetation near beaver ponds doesn’t experience as much reduced water availability during drought (Macfarlane et al. 2016, Pilliod et al. 2017, Fairfax and Small 2018; Fig. 1, middle). Drought‐stricken vegetation burns more easily than lush, green vegetation (Liu et al. 2010), so it follows that the vegetation around beaver ponds would be more difficult to burn than vegetation around undammed creeks (Fig. 1, bottom). Although this concept has been observed, discussed, and documented in photographs (Fig. 2), the potential difference in vegetation health during wildfire in areas with and without beaver has not yet been quantified (Foster et al. 2020). In this study, we use satellite‐derived Normalized Difference Vegetation Index (NDVI) data from the year before, year of, and year after a major wildfire to examine the vegetation changes of riparian corridors with and without beaver. We include data from five large wildfires located in five different western U.S. states, Colorado, California, Oregon, Idaho, and Wyoming, to quantify the extent to which, if any, vegetation in beaver‐dammed riparian areas can stay green during wildfire…”
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