Geography Theses and Dissertations

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High Resolution Remote Sensing of Eelgrass (Zostera marina) in South Slough, Oregon
(University of Oregon, 2020-09-24) Anderson, Riley; Fonstad, Mark
Eelgrass (Zostera marina) supports aquatic biodiversity, carbon sequestration, aquaculture, and water quality. Eelgrass has been undergoing global decline for more than three decades. Lack of spatially extensive, long-term monitoring data is limiting eelgrass conservation and restoration projects, which have low success rates in the Pacific Northwest. This study compares pixel- and object-based image classification techniques on high spatial resolution drone and aerial imagery of eelgrass in South Slough, Oregon. It also quantifies change in spatial distribution and geometry over a three-year period. I find that low-cost imagery can recognize low eelgrass coverage in Pacific Northwest tidal marshes with moderate success. Both classification algorithms overestimated coverage by misidentifying algae as eelgrass and neither consistently performed best for eelgrass mapping. I detected a 44.8% net loss in coverage between 2016 and 2019. Increasing patch shape complexity and fragmentation in areas of decline suggest that disturbances are affecting landscape and patch-level eelgrass factors.