The biodiversity of migratory waders and ecosystem services of tidal flat along the East Asian-Australasian migratory bird flyway under current and future climate and development scenarios

Abstract

The East Asian-Australasian Flyway (EAAF) is one of the nine major flyways in the world. The millions of migratory birds are fast declining due to habitat loss and other threats. This thesis provides broad-scale spatial planning input for conservation management of the EAAF, focusing on improving understanding of distribution of wader biodiversity hotspots at the flyway scale; predicting how these might change due to climate change and coastal development; and, making an initial assessment of the ecosystem services that waders and tidal flats provide.

I used species-distribution modelling (MaxEnt) to develop temporally explicit individual range maps for 57 migratory wader species across their annual cycle, and to generate biodiversity hotspot maps of these birds along the EAAF. The results indicated a higher and spatially different species-richness pattern compared to a wader biodiversity hotspot map based on BirdLife International range maps, indicating that the richness of the EAAF may have been underestimated and certain hotspots (e.g. around the Yellow Sea) overlooked. Less than 10% of the inland and coastal areas which support waders are protected and, only 5% of areas with the top 10% of species richness is protected. The results underscore the need to increase the coverage of the current protected-area network to achieve Aichi Biodiversity Target 11 for flyway countries, especially around the identified hotspots, and giving stronger consideration to the temporal dynamics of wader migration.

Comparing the current wader distribution across the EAAF with two climate-change scenarios (RCP 4.5 and RCP 8.5, both including a 1 m sea-level rise by 2070), there was an evident northward range shift of wader distributions. Breeding grounds in Alaska and Siberia were projected to have a higher richness, whereas Mongolia, parts of northern China, and the lower Mekong basin will undergo significant losses. Sea-level rise and coastal development will limit wader habitat, while species richness inland is also projected to decline, particularly in the lower Mekong basin. To mitigate these effects, coastal-zone management along the EAAF must prioritize protection of natural shoreline and enhance management of habitat inland, such as wet agricultural areas, which will help maintain connectivity along the flyway.

A database on studies of ecosystem-services valuation of tidal flats across the EAAF was constructed, containing 122 value estimates; the median value was 935 USD/ha/yr. Multiple-regression analysis revealed the key determinants of ecosystem services values (ESV) of tidal flats along EAAF. Socioeconomic variables (i.e. night-time light, a proxy of economic development, and per capita GDP) were significant contributors to ESV, while biophysical variables (including biodiversity) had limited influence. Based on these results, an illustrative assessment of ESV of EAAF tidal flats was conducted using benefit transfer. Tidal flats in regions with more intense economic development had higher ESV: for instance, the Pearl River Delta near Hong Kong and Shenzhen, or Republic of Korea close to Seoul. Some areas with high biodiversity and ecological significance for the EAAF were not among those identified having high ESV, highlighting the spatial misalignment between ecosystem-services provision and biodiversity richness at some sites.