International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 217-228 http://ecoevopublisher.com/index.php/ijmec 21 9 Figure1 Examples of dam construction and channel avulsion resulting from beaver dam construction from the River Otter catchment, England (Adopted from Brazier et al., 2021) Image caption: (a) shows an example where a divergent flow path has re-entered the main channel resulting in head-cut erosion. Panel (b) shows the type of multi-thread channel form that occurs downstream of dams in wide, low gradient floodplains. Panel (c) shows a beaver dam on a 4th order stretch of river (Adopted from Brazier et al., 2021) Beavers' feeding and gnawing on trees along riverbanks can also significantly alter the structure of forests. After being gnawed, trees leave behind a large number of fallen logs and stumps. These wooden remnants provide shelter for decaying wood invertebrates such as beetles, and also become ideal habitats for birds such as woodpeckers and small mammals (Brazier et al., 2021). Studies have shown that in the area where beavers are active, the canopy gap increases, the number of fallen trees rises, the understory vegetation prospers accordingly, and plant diversity is enhanced (Orazi et al., 2022). In addition, beaver projects have strengthened the coupling between land and water: they transport timber by excavating channels and gullies and channel river water into woodlands, making the connection between rivers and floodplains closer (Grudzinski et al., 2022). In the long term, these activities have promoted vegetation succession and the reshaping of ecosystems (Fairfax and Westbrook, 2024). 2.3 The spatiotemporal scale and persistence of beaver engineering Beavers' environmental transformation has a unique spatial range and temporal dynamics. Spatially, the activities of individual beaver families typically extend several hundred to several thousand meters along streams, and their dam-building effects are mostly confined to the lower reaches of small watersheds (Halley et al., 2021). However, in regions rich in water resources, when multiple families are distributed along the river, their engineering effects will superimpose and then extend to the entire basin (Wrobel, 2020). Take the Northern Slope of Alaska as an example. In recent decades, beavers have moved into the tundra. Satellite images show that tens of thousands of new DAMS have been built locally and the number of ponds has almost doubled, causing significant disturbances
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