Date of Award:

5-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Robert Al-Chokhachy

Committee

Robert Al-Chokhachy

Committee

Nicolaas Bouwes

Committee

Hayley Glassic

Committee

Trisha Atwood

Abstract

Networks of rivers and their floodplains (i.e., low-lying areas adjacent to rivers and streams that could plausibly flood) have been degraded, reducing the availability of freshwater and habitat for people and wildlife. Therefore, land managers are pursuing cost-effective restoration strategies, including partnering with beavers (Castor canadensis), to promote the health of these ecosystems and associated benefits. However, our understanding of beaver-mediated restoration benefits remains incomplete. Here, we compared locations along streams with and without beaver dams to measure the benefits of beavers in the Great Basin of the Western United States. We measured the effects of beaver dams on i) stream depths and depth variability, interactions between the stream and surrounding floodplains, and water movement as ecosystem health indicators; and ii) number of unique species, diversity, and activity levels for various fish, bat, and bird taxa as biodiversity indicators. We further investigated how the benefits of beavers varied by dam status (i.e., actively maintained or abandoned), and across valley settings, from steep and narrow valleys to low-gradient and wide valleys. Our results showed deeper and more variable stream habitats, stronger connections between streams and floodplains, and slower-moving water in stream segments with beaver dams than in segments without. Importantly, we found that the benefits of beaver activity are influenced by valley setting and that many benefits persisted even after dam abandonment. Although we found little difference in biodiversity indicators, the benefits of beaver dams to other components of ecosystem health likely contribute to diverse habitats that benefit biodiversity beyond individual stream segments. As interest in nature-based restoration grows, understanding the variable effects that beavers have on ecosystem processes within and across regions can inform the feasibility, potential effectiveness, and benefits of beaver-mediated ecosystem health restoration.

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