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

based on the approval of the Town Planning Board. Thus, there is an imminent danger of the fishponds being converted into hard infrastructure, including high rise buildings. Such devel- opment will result in loss of potential habitat and conservation opportunities, and also create hard, impervious surfaces that effectively cause flooding elsewhere, and will be more difficult and economically unviable to restore back to wetlands in the future. An analysis of coastal squeeze in the Yellow River Delta has shown that farmlands, including those claimed from wetlands, allowed the potential for wetland migration and restoration because they are more pervious, relative to wetlands that had been converted to hard infrastructure [58]. Ecosystems as climate proofing solutions for Hong Kong and the Greater Bay Area Coastal wetlands are among the most productive and important ecosystems in the world [59]. In addition to supporting high biodiversity, they also provide a variety of ecosystem goods and services, including reducing flooding, protecting shorelines from wave and tidal surges expected from the more severe weather events due to climate change [3, 6, 14]. Thus, climate- smart land use strategies that prevent the conversion of wetlands can increase coastal resilience and diminish the vulnerability of coastal communities and infrastructure from the conse- quences of SLR and storms that make landfall [6, 60, 61]. According to the ADB [62] the economic losses from floods in the Asia-Pacific region

could increase from the $6 billion per year in 2005 to $52 billion by 2050, and 13 of the top 20 cities with the largest predicted increase in annual losses will be in the Greater Bay Area. This area is also recognized as the main landfall area of tropical cyclones and typhoons from the Northwest Pacific and the South China Sea, with the typhoons being stronger and more intense, and accompanied by stronger storm surges [63]. Records from 1991 and 2005 show that storm surges, in effect, created a SLR of between 1.9 and 2.6 m in the Pearl River Delta [64], while severe typhoons can create surges that are as high as 4 m [22]. Thus, much of the Pearl River Delta and Greater Bay Area could be vulnerable to extreme weather events exacer- bated by climate change, including SLR, floods caused by wave surges, saltwater intrusion, and an increase in the severity of storms [21, 22]. Coastal wetlands also buffer and attenuate storm surges and reduce property damage and loss of lives along the coastlines [65–69]. However, rapid economic development and popula- tion growth over the past four decades have resulted in widespread conversion and fragmenta- tion of natural coastal habitats in the Greater Bay Area, making it more prone and vulnerable to these natural disasters, especially floods [70]. Removal of infrastructure to restore wetlands as climate buffers will be very expensive [71, 72]. Thus, forward-looking, proactive land-use planning for coastal areas that include climate impact analyses and nature-based solutions will

be far more cost effective; the costs of failing to do so could be greater [14, 44, 73–77]. Conserv- ing the existing coastal wetlands and preventing further conversion as an integrated climate response is an obvious choice. Climate proofing the flyway The application of the SLAMM demonstrates the conservation opportunities for a climate adaptation strategy to ensure that Mai Po will continue to host migratory birds in the future. However, Mai Po is only one steppingstone along this vast corridor that is the EAAF, with hundreds of other such steppingstone wetlands that are also threatened by encroaching infra- structure and climate change [78]. The flyway needs all, or several strategically placed step- pingstones to be functional to support the migration phenomenon [3, 43, 51]. Therefore, we recommend that this analysis be applied to the other wetlands that serve as strategic staging or 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 12 / 16