Event Title

Roads to ruin: the threats of urbanization to conservation of a sentinel species

Presentation Abstract

Since the late 1990s, coho salmon adults returning to their natal urban streams in Puget Sound experience high rates (e.g., 40-90% across a total run) of spawner mortality syndrome. Evidence to date suggests that toxic urban stormwater runoff is the likely causative agent and that this high mortality may threaten wild coho populations, particularly in urbanizing basins. The ability to identify basins currently at risk for this syndrome is critical to conservation efforts. We looked at the relationship between the mortality syndrome (time series of coho spawner survey data from 51 streams distributed across an urban gradient in the Puget Lowlands) and basin scale habitat conditions (time series of nationally available geospatial data, including seasonal precipitation) to better understand the landscape characteristics most associated with the syndrome and to generate predictive maps of mortality rates in unmonitored basins. Structural equation modeling revealed a latent urbanization gradient that was associated with road density and traffic intensity, among other variables, and positively related to mortality, which is consistent with other studies that suggest motor vehicles are the likely source of a chemical mixture that washes off urban landscapes into coho spawning streams. Across years within sites, mortality increased with summer and fall precipitation, but the effect of rainfall was strongest in the least developed areas and was essentially neutral in the most urbanized streams. We used the best-supported structural equation model to generate a predictive mortality risk map for the entire Puget Sound Basin. The predictive mortality map identified likely hotspots for coho spawner die-offs in unmonitored basins across the gradient of urbanization in Puget Sound. Our analyses improve our understanding of the interplay between urbanization and climatic drivers of the mortality syndrome, are easily transferable to other regions, and can be used for siting green stormwater infrastructure in the current built environment and in future development scenarios.

Session Title

Biological Indicators of Stormwater Impacts and Mitigation Effectiveness in the Salish Sea

Conference Track

SSE3: Fate, Transport, and Toxicity of Chemicals

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE3-478

Start Date

6-4-2018 8:30 AM

End Date

6-4-2018 8:45 AM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 6th, 8:30 AM Apr 6th, 8:45 AM

Roads to ruin: the threats of urbanization to conservation of a sentinel species

Since the late 1990s, coho salmon adults returning to their natal urban streams in Puget Sound experience high rates (e.g., 40-90% across a total run) of spawner mortality syndrome. Evidence to date suggests that toxic urban stormwater runoff is the likely causative agent and that this high mortality may threaten wild coho populations, particularly in urbanizing basins. The ability to identify basins currently at risk for this syndrome is critical to conservation efforts. We looked at the relationship between the mortality syndrome (time series of coho spawner survey data from 51 streams distributed across an urban gradient in the Puget Lowlands) and basin scale habitat conditions (time series of nationally available geospatial data, including seasonal precipitation) to better understand the landscape characteristics most associated with the syndrome and to generate predictive maps of mortality rates in unmonitored basins. Structural equation modeling revealed a latent urbanization gradient that was associated with road density and traffic intensity, among other variables, and positively related to mortality, which is consistent with other studies that suggest motor vehicles are the likely source of a chemical mixture that washes off urban landscapes into coho spawning streams. Across years within sites, mortality increased with summer and fall precipitation, but the effect of rainfall was strongest in the least developed areas and was essentially neutral in the most urbanized streams. We used the best-supported structural equation model to generate a predictive mortality risk map for the entire Puget Sound Basin. The predictive mortality map identified likely hotspots for coho spawner die-offs in unmonitored basins across the gradient of urbanization in Puget Sound. Our analyses improve our understanding of the interplay between urbanization and climatic drivers of the mortality syndrome, are easily transferable to other regions, and can be used for siting green stormwater infrastructure in the current built environment and in future development scenarios.