Losing tidal wetlands in the midpoint of East Asian-Australasian Flyway in the pasting 100 years

Abstract

Abstract Migratory shorebirds rely on tidal flats as stopover sites for refueling and wintering. Taiwan is in the middle of the East Asian–Australasian Flyway, where the sandy/muddy shores on the western coast support thousands of migratory birds with important stopover habitats. Among these habitats, tidal flats are the most crucial habitats for shorebird survival. However, in the last century, the landscape has been largely altered for agriculture, aquaculture, and industrial development. To assess the current status of shorebird habitats, we evaluated landscape changes between the 1920s and 2020s based on historical topographic map data, Landsat Archive images, and the Normalized Difference Water Index. Our analysis showed that the area of tidal flats increased before the 1950s but has decreased since the 1980s. The area dropped rapidly from 459.72 km2 to 194.05 km2, and almost 60% of the tidal flat coverage has been lost in the last 60 years. These results indicate that the tidal wetlands in western Taiwan have reached an endangered status, as per the International Union for Conservation of Nature Red List of Ecosystems criteria. Although the decrease in speed seems to have slowed in recent decades, energy and industrial development still threaten tidal wetlands.