Long-term Trends in Eelgrass Distribution and Coastal Development of the Salish Sea

In the Salish Sea, eelgrass meadows provide structurally complex habitat for a myriad of fish and invertebrate species, supporting marine ecosystems and stabilizing coastal sediments. Seagrasses of all species however, are in worldwide decline as increasing coastal development threatens the function and diversity of nearshore marine ecosystems. Long-term studies of the spatio-temporal dynamics of eelgrass in the Salish Sea are an important step in identifying contributing factors to eelgrass decline, and developing effective conservation and restoration strategies. One such dynamic to quantify are the impacts of coastal development on the distribution and trends of eelgrass ecosystems. Utilizing a historic aerial photography dataset covering the Southern Gulf Islands, BC over the years of 1932 to 2014, eelgrass beds were mapped using digital image classification methods for selected sites within the region. Through the application of a GIS change analysis, trends in eelgrass distribution were characterized and compared to changes in shoreline development and land use change in adjacent catchment areas. The results of this analysis can be applied to education, conservation, and restoration practices to prevent further eelgrass decline in the Salish Sea and beyond