COS 110-3 - Projecting impacts of future sea level rise on intertidal habitat for migratory shorebirds in the Fraser River estuary, British Columbia, Canada

Background/Question/Methods

Climate change is one of the most pervasive threats to the persistence of coastal marine biodiversity, and climate change-associated sea level rise (SLR) poses serious risks to nearshore ecosystems. Tidal flats, which serve as critical habitat for migratory shorebirds along the world’s major flyways, are particularly at risk. The Fraser River estuary (FRE) in British Columbia, Canada is a key stopover site on the Pacific Flyway and an area of global significance for over 1 million shorebirds, which use the site to refuel during spring and fall migration. Although the impacts of SLR have been examined for other key sites along the flyway—with the projected loss of 18–70% of intertidal habitat along the western coast of the United States by 2100—the effects of SLR on coastal habitat in the FRE remain largely unknown. Here, we modelled changes in the availability of intertidal habitat in the FRE resulting from projected rates of regional SLR. We used local habitat maps to identify tidal flats within the southern FRE (Boundary Bay, Roberts Bank, and Sturgeon Bank), then integrated this information with tidal data and a high-resolution digital elevation model to project changes in habitat availability with 1 m of SLR.

Results/Conclusions

We found that an increase in sea level of 1 m by 2100 may lead to the loss of 54.96 km² of intertidal habitat (30.83% of current extent) in the FRE. Over half of the projected losses (-29.15 km²) occurred at Roberts Bank, a hotspot for migrating Western sandpiper, suggesting that losses in key areas may disproportionately affect certain species. In addition, the potential for habitat migration with SLR is likely to be extremely limited throughout the region due to the presence of dykes along much of the estuary shoreline. The substantial loss of tidal flat habitat in key areas of the FRE will likely impair the ability of this site to continue to host large numbers of migratory shorebirds, with serious implications for the stability of the intercontinental Pacific Flyway.