A climate adaptation strategy for Mai Po Inner Deep Bay Ramsar site: Steppingstone to climate proofing the East Asian-Australasian Flyway

flooded marshes inside the nature reserve will also be inundated even with an 8 mm/yr accre- tion rate and less (Table 2). Under a 2 m SLR scenario, during high tide over 77% of the tidal flats and about half of the mangroves and marshes will be inundated even with a 15 mm accre- tion rate (Table 2). If the accretion decreases to 4 mm/yr or less, most of the marshes, man- groves, and tidal flats will be underwater. Discussion Long distance animal migrations are some of Nature’s more wondrous phenomenon. But across the world these migrations are threatened by habitat loss, barriers that constrain or pre- vent movement, hunting [38], and now, climate change [11]. The EAAF is one of nine major long-distance corridors for migratory waterbirds that covers a swath over East, Southeast and eastern parts of South Asia to include 22 countries from Arctic Russia and USA (Alaska) to Australia and New Zealand [39]. The wetlands that lie scattered through this vast landscape, especially along the coastal areas, represent steppingstones where the waterbirds, which com- prise a large group of the migrants, can rest, refuel, and continue on their journey, or provide winter habitats [40]. But the ecological functionality of the flyways that have evolved over millennia are now threatened [6, 8, 9, 41, 42]. Asia’s coastal areas are among the most densely populated areas, and urban and industrial infrastructure is rapidly expanding at the expense of the natural eco- systems disregarding the importance of the ecosystem services these wetlands provide and the

longer term economic and social consequences of losing them [5, 8, 43–46]. Over 80% of East and Southeast Asia’s wetlands are now classified as threatened and nearly half of all tidal flats have already been lost [4]. Thus, many of the migratory waterbirds that depend on the wet- lands along the EAAF are now facing population declines as important and strategic stopover and winter sites continue to disappear [1, 4, 8, 35]. While over 5 million individuals from 58 species of shorebirds are known to use the EAAF, it now has the highest number of threatened species and declining populations [47]. Analyses have shown that less than 10% of the wetlands that support waterbirds are protected, and many important yet unprotected areas are vulnera- ble to anthropogenic threats [3, 34, 48]. Thus, given the rapid loss of wetlands, inadequate pro- tection and conservation management and consequent erosion of ecological connectivity and functionality of the flyway, it is important to secure the remaining wetlands to ensure that the migrations persist [35]. In addition to protection to prevent anthropogenic conversion, the wetlands and the flyway also require a ‘climate-smart’ conservation paradigm [49–51]. As transitional ecosystems between terrestrial and marine systems, coastal wetlands are vulnerable to SLR and the severe storms and associated strong wave surges expected from climate change on one side, and con- tinued land conversion in the terrestrial realm [52, 53]. With SLR, coastal wetlands could

migrate further inland [48, 54]. But if the adjacent terrestrial areas are converted to anthropo- genic land uses this migration will be constrained and the wetlands will be lost due to coastal squeeze [48, 55]. As strategic wetlands along the flyway are lost to development and climate change and consequent environmental impacts, the functionality of the flyway will become degraded, and the migration phenomenon could eventually cease. Climate smarting the wetlands: The case of the Mai Po Inner Deep Bay Ramsar site As an important steppingstone and wintering wetland for waterbirds along the EAAF, Mai Po represents a case study of how a climate adaptation strategy can be integrated into conserva- tion management. The results from our climate model shows that over 230 ha of tidal flats, PLOS ONE Climate adaptation strategy for Mai Po Inner Deep Bay Ramsar site PLOS ONE | https://doi.org/10.1371/journal.pone.0239945 October 21, 2020 10 / 16