Program on the Environment

Eelgrass (Zostera marina) provides critical ecosystem services in shallow coastal waters, including marine habitat, erosion control, carbon sequestration, and water filtration. Since the 2000–2008 baseline, eelgrass populations in the San Juan Archipelago have declined significantly, with recreational boating identified as a key pressure alongside disease and ocean warming. This study developed a replicable, data-driven framework for measuring potential recreational boating pressure on eelgrass habitat using Automatic Identification System (AIS) data across six bays in the San Juan Islands from 2018 to 2024. Conducted through a research internship at Friday Harbor Laboratories (FHL) at the University of Washington, the project translated raw AIS data into quantifiable boating variables — including vessel speed, vessel classification, and anchoring frequency — to assess spatial and temporal patterns of boating activity. These variables were integrated into a stressor metric to generate comparable risk scores across bays, while GIS mapping overlaid eelgrass transect and bathymetry data to visualize overlap between boating pressure and optimal eelgrass growth zones. Results revealed a sharp increase in boating activity during 2020–2021, likely driven by pandemic-related shifts in outdoor recreation, with stressor scores in some bays more than doubling. These findings provide a scalable foundation for targeted coastal policy and conservation planning across the Puget Sound region. By identifying which bays face the greatest boating-induced stress, this framework can support resource managers in prioritizing protection efforts, informing site-specific regulations, and guiding future eelgrass restoration in areas where habitat recovery is possible.