Ecosystem services assessment based on emergy accounting in Chongming Island, Eastern China

Chongming Island, the largest alluvial island in the world, is an ecologically sensitive area. Due to its green space, farmland, estuaries and coastal wetlands and its proximity to the city of Shanghai (45 km, home to 24.2 million people), the island supports important agricultural and fisheries economies. This paper carries out an evaluation of the ecosystem services (ES) on Chongming Island, Shanghai, based on the emergy analysis method, identifying the service supply and flow between ecosystems and urban area. Results show that from the ecosystem-type perspective, the tidal wetland ecosystem provides the most service to Chongming Island, accounting for 45.2% ES emergy in 2012, followed by the agricultural ecosystem (34.5%) and the freshwater wetland ecosystem (6.3%). From ecosystem service-type perspective, water supply, flood storage and aquatic product supply are the main emergy outputs of the wetland ecosystem and account for 51.1%, 17.6% and 25.2% of the emergy, respectively. Food supply is the main emergy of the cropland ecosystem output and accounts for 58% of the emergy. Organic matter production and water retention are the main services provided by the forest ecosystem, accounting for 33.6% and 30.0% of the total emergy respectively. Based on the systematic emergy dynamic analysis, on the one hand, the wetland and forest ecosystems played more significant roles in water supply and retention while the cropland ecosystem had a less important role in food supply from 2002 to 2012. On the other hand, the urban ecosystem has gradually transformed from a positive to a passive participant in the role of supplier and user for ecosystem services. Finally, policy options are proposed to promote land use planning and restore/maintain ecosystem services.