Fall Semester 2024

The impact of beavers on blue-green ecosystems
Valentin Moser

Beavers influencing bat presence. Beaver influence bat activity directly and indirectly through the change of the environment, leading to an increased habitat heterogeneity and changed arthropod community © Valentin Moser

As ecosystem engineers, beavers (Castor fiber) modify aquatic (blue) and terrestrial (green) ecosystems through building dams and felling trees. The resulting elevated water level and open canopy can benefit different species groups and communities. However, compared to aquatic taxa, the impacts of beaver-engineering on terrestrial taxa and across the blue-green gradient are poorly understood. In my PhD, we sampled biodiversity together with ecosystem properties like soil and water chemistry, as well as ecosystem functions like decomposition rates in 16 systems across Switzerland to better understand how beavers change ecosystems. For bats, our results show correlations between beaver activities and a higher bat presence in these systems. Beaver engineering changes habitat heterogeneity and arthropod abundance, correlated with higher bat species richness, bat activity, and feeding activity. The volume of standing deadwood, a critical resource for bat roosting and foraging, had the strongest correlations with bat presence. Our findings suggest that beavers create heterogeneous landscapes that offer highly diverse ecological niches. By creating environments rich in resources and complexity, beavers may act as natural restoration agents, supporting diverse populations of bats and other species groups. Our results could underscore the importance of integrating beaver management into conservation strategies to restore and enhance aquatic and riparian ecosystems.

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