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

RESEARCH ARTICLE A climate adaptation strategy for Mai Po Inner Deep Bay Ramsar site: Steppingstone to climate proofing the East Asian-Australasian Flyway Eric WikramanayakeID1*, Carmen Or1, Felipe Costa2, Xianji Wen1, Fion Cheung1, Aure´lie ShapiroID2,3 1 WWF Hong-Kong, Hong Kong, Hong Kong SAR, 2 WWF-Germany Space+Science, Berlin, Germany, 3 Here+There Mapping Solutions, Berlin, Germany * ericw@wwf.org.hk Abstract The ecological functionality of the East Asian-Australasian Flyway is threatened by the loss of wetlands which provide staging and wintering sites for migrating waterbirds. The disap- pearance of wetland ecosystems due to coastal development prevents birds from complet- ing their migrations, resulting in population declines, and even an eventual collapse of the migration phenomenon. Coastal wetlands are also under threat from global climate change and its consequences, notably sea level rise (SLR), extreme storm events, and accompa- nying wave and tidal surges. The impacts of SLR are compounded by coastal subsidence and decreasing sedimentation, which can result from coastal development. Thus, important wetlands along the flyway should be assessed for the impacts of climate change and coastal subsidence to plan and implement proactive climate adaptation strategies that include habi- tat migration and possibility of coastal squeeze. We modelled the impacts of climate change and decreasing sedimentation rates on important bird habitats in the Mai Po Inner Deep Bay Ramsar site to support a climate adaptation strategy that will continue to host migratory

birds. Located in the Inner Deep Bay of the Pearl River estuary, Mai Po’s tidal flats, coastal mangroves, marshes, and fishponds provide habitat for over 80,000 wintering and passage waterbirds. We applied the Sea Level Affecting Marshes Model (SLAMM) to simulate habitat conversion under two SLR scenarios (1.5m and 2.0m) for 2050, 2075, and 2100 for four accretion rates (2mm/yr, 4 mm/yr, 8 mm/yr, 15 mm/yr). The results showed no discernible impact to habitats until after 2075, but projections for 2100 show that the mangroves, marshes and tidal flats could be impacted in almost all scenarios of SLR and accretion. Under a 1.5m SLR scenario, even at low tide, if accretion levels decrease to 4 mm/yr, the tidal flats will be inundated and with a 2 mm/yr accretion the mangroves will also be inun- dated. Thus, important shorebird habitats will be lost. During high tide the ponds inside the nature reserve, which are intensively managed to provide high tide roosting sites and other habitats for waterbirds, will also be inundated. Thus, with a 1.5m SLR and declining sedi- mentation the migratory shorebirds will lose habitat, including the high tide roosting habitats inside the nature reserve. The model also indicates that the fishponds further inland in the PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0239945 October 21, 2020 1 / 16 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Wikramanayake E, Or C, Costa F, Wen X, Cheung F, Shapiro A (2020) A climate adaptation strategy for Mai Po Inner Deep Bay Ramsar site:

Steppingstone to climate proofing the East Asian- Australasian Flyway. PLoS ONE 15(10): e0239945. https://doi.org/10.1371/journal.pone.0239945 Editor: Yong Zhang, Nanjing Forestry University, CHINA Received: April 29, 2020 Accepted: September 15, 2020 Published: October 21, 2020 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0239945 Copyright: © 2020 Wikramanayake et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: The land use data in Fig 1 are prepared by WWF Hong Kong, and was also used to derive the model outputs in Figs 2 and 3. The data are available here: https://globil-panda.