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Introduction
Tidal flats play important economic and ecological roles in coastal ecosystems (Costanza et al. 1997), such as filtering organic wastes (Widdows et al. 2004), and provide abundant nutrients that support microbenthic organisms, fish, birds, and even humans (Levin et al. 2001, Wall et al. 2001). In particular, tidal flats on the west coast of South Korea are prominent staging sites for migratory shorebirds that use the East Asian-Australasian (EAA) Flyway (Barter 2002, Hua et al. 2015). Several hundreds of thousands of shorebirds, including several endangered and threatened species, use the EAA Flyway to migrate thousands of kilometres, often travelling from as far as Australia to Siberia and back again. Many of these migrants use tidal flats on the west coast of Korea as stop-over sites for the replenishment of energy stores necessary for continuation of their journey (Barter 2002, Moores 2006, Rogers et al. 2006, Buehler and Piersma 2008, Warnock 2010). However, many staging sites in South Korea have been greatly reduced in size owing to land-reclamation projects, with grave implications for many of the migratory shorebird species that travel along the EAA Flyway.
Whereas reclamation projects in north-western Europe must adhere to strict guidelines and restrictions designed to minimise potentially harmful effects (Piersma 2009), large-scale reclamation projects in Korea are conducted under laws that date back to 1962, and consequently many ecologically important tidal flats have vanished over the past several decades owing to reclamation. The Saemangeum, a bay-shaped tidal flat, has long been used as a staging ground by hundreds of thousands of migrating shorebirds (Moores 2006, Rogers et al. 2006); however, the Saemangeum Seawall Project, in which a 33-km sea wall was constructed to isolate the tidal flat from the Yellow Sea, was completed in 2006, with construction of an accompanying sluice gate system to control the water levels in Saemangeum continuing until 2010. As of 2014, ∼400 km2 of the estuarine tidal flats were isolated from the sea, with ∼160 km2 of the flats reclaimed.
Several studies have highlighted the adverse impacts that coastal reclamation has had on ecosystems and the organisms they support, and consequently on humans as well (Laursen et al. 1981, Goss-Custard and Yates 1992, Li 2010, Yang et al. 2011, Wang et al....