The Effect Of Agricultural And Aquaculture Areas On Waterbirds In The Reclaimed Coastal Wetland Of Pudong Dongtan,Shanghai

Wetland ecosystem is known as the "kidney of the earth", providing rich biodiversity and ecosystem service of high value. As the vital part of wetland, the tidal flats have complex landform characteristics and potentially economic profits. In order to meet the needs of land utilization, tidal flat reclamation shows the significant importance in regional economy of Shanghai, that recently undergoing a rapid development.Pudong Dongtan, a coastal wetland of the Yangtze River Estuary, is not only an international vital bird stopover site for migratory birds, but also key area available to sustainable reclamation. The reclaimed coastal wetland is used for a variety of land development and utilization, including aquaculture and agricultural areas. In order to explore the effects of agricultural and aquaculture areas to waterbirds in Pudong Dongtan wetland, three study areas (natural tidal flats, aquaculture and agricultural areas) were selected to investigate the waterbird community diversity.Waterbird surveys as well as habitat investigations were carried out in2012(in spring and autumn) and2013(in winter) to compare differences in the waterbird diversity between agricultural and aquaculture areas, and then the waterbird distributions among different habitats in agricultural area.The main results of this study are as follows:1. Waterbird community structureA total of54bird species corresponding to10families and5orders, were recorded in Pudong Dongtan during migratory seasons, in2012. In natural tidal flat,30species were recorded, belonging to6families and3orders (Podicipediformes, Ciconiiformes and Charadriiformes). In aquaculture area,31species were recorded, belonging to9families and5orders (Podicipediformes, Ciconiiformes, Anseriformes, Gruiformes and Charadriiformes). In agricultural area,15species were recorded, belonging to6families and3orders (Ciconiiformes, Anseriformes, and Charadriiformes).A total of21species corresponding to8families and6orders were recorded in the winter,2013. In aquaculture area,20species were recorded, belonging to7families and6orders (Podicipediformes, Pelecaniformes, Ciconiiformes, Anseriformes, Gruiformes and Charadriiformes). In agricultural area,9species were recorded, belonging to4families and4orders (Podicipediformes, Ciconiiformes, Anseriformes, and Charadriiformes).2. Waterbird diversities in different sites in migratory seasonsIn migratory seasons (spring and autumn), shorebirds with small groups were found in the natural tidal flat and bare land in agricultural area. However, herons were recorded in various habitats. Significant difference was only observed in waterbird density among research sites during spring (x2=16.761. p<0.01) and autumn (x2=7.867, p<0.05), but not observed in waterbird species, diversity and evenness.3. Waterbird community diversities in different sites in winterPudong Dongtan is a wintering area for Anatidae birds. Compared to agricultural area, waterbird species, density, diversity and evenness tended to be higher in aquaculture area, but significant differences in their species, density, diversity and evenness were not observed between agricultural and aquaculture areas in winter. In agricultural area, waterbird species, density, diversity and evenness were highest in planting area (all p<0.01) than in aqueducts and watercourse.4. Waterbird distribution patterns in various habitats of agricultural areaDuring migratory seasons (spring and autumn), most waterbird species were noted in aqueducts. Most waterbirds observed in bare land were shorebirds, while some herons were also observed. However, only herons were observed in planting area in agricultural area and watercourse. Significant differences in frequencies of waterbird populations were observed among various habitats (x1=521.53, df=45, p<0.01). Relationship between shorebird populations (species, density, H and J) and their habitat factors (the average water level, the average height of the vegetation, vegetation cover and bare land area) were analyzed in autumn in agricultural area. Results indicated that the shorebird density was positively correlated with bare land area in autumn, whereas significant correlation was not observed with other environmental factors. Shorebird species, density, diversity and evenness were negatively correlated with the average water level, the average height of the vegetation and vegetation cover, indicating that shorebirds would be noted in the area with low water level, low height of vegetation and low vegetation cover. Shorebird species and diversity were negatively correlated with bare land area in planting area. According to present results, if planting area in the agricultural area was planned and managed rationally, it would play an important role for waterbird conservation. According to the demands of migratory waterbirds for habitat factors, shallow water in aqueducts and a certain area of bared mudflats can be maintained in spring, and appropriate bare land patches can be configured in planting area in autumn. These habitats would be served as shorebird suitable habitats to compensate for their natural habitat loss.