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Beaver in tidal habitat: Examples from the Pacific Northwest
1Skagit River System Cooperative, Burlington, Washington, United States of America.
Plos One
|July 8, 2026
Summary
Beaver are adapting to tidal estuaries, building dams that significantly alter these coastal wetlands. Their presence and dam structures suggest a comparable ecosystem engineering role to freshwater systems.
Area of Science:
- Ecology
- Environmental Science
- Wildlife Biology
Background:
- Beaver (Castor canadensis) are recognized as keystone ecosystem engineers, primarily in fluvial and lacustrine environments.
- Their dams transform lotic (flowing) habitats into lentic (still) ones, profoundly impacting ecosystem structure and function.
- This study investigates beaver adaptability and ecological role in previously underappreciated tidal wetland habitats.
Purpose of the Study:
- To document the widespread presence and habitat use of beaver in Pacific Northwest tidal river deltas and estuaries.
- To quantify the characteristics of beaver dams and associated pools in tidal systems.
- To assess the potential ecosystem significance of beaver in estuarine environments.
Main Methods:
- Field observations and channel profile surveys using real-time kinematic (RTK)-GPS in tidal wetlands.
- Analysis of Google Earth aerial imagery dating back to 1990 to determine dam persistence.
- Comparative analysis of dam and pool metrics against existing fluvial and lacustrine beaver data.
Main Results:
- Beaver dams are prevalent in oligohaline to fresh tidal systems with significant tidal ranges (1.5–5.0 m).
- Tidal beaver dam density exceeded fluvial records, with dams impounding water primarily at low tide.
- Dam and pool dimensions (head, height, depth, area) were comparable to fluvial systems, suggesting significant ecological impact.
Conclusions:
- Beaver demonstrate remarkable adaptability, colonizing and engineering tidal estuarine habitats.
- Tidal beaver dams can persist for decades, indicating long-term ecosystem modification.
- Understanding beaver distribution and impact in tidal wetlands is crucial for effective estuarine habitat restoration, benefiting species like salmon.
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