Waterbird Population Changes in the Wetlands at Chongming Dongtan in the Yangtze River Estuary, China

Coastal Ecosystems Research Station of Yangtze River Estuary, Institute of Biodiversity Science, Fudan University, Shanghai, People's Republic of China.
Environmental Management (Impact Factor: 1.72). 02/2009; 43(6):1187-200. DOI: 10.1007/s00267-008-9247-7
Source: PubMed


We studied the changes in wetland habitats and waterbird communities between the 1980s and the 2000s at Chongming Dongtan, a Ramsar site in the Yangtze River estuary, an ecologically important region. This region is an important stopover site for shorebirds along the East Asian-Australasian flyway and is extensively used by waterfowl. A net loss of 11% of the wetland area was estimated during study periods at Chongming Dongtan. The change was dependent on wetland types: while the area of artificial habitats such as paddy fields and aquacultural ponds more than doubled, more than 65% of natural habitats including sea bulrush (Scirpus mariqueter) and common reed (Phragmites australis) marshes were lost over the two decades. An exotic plant species introduced from North America, smooth cordgrass (Spartina alterniflora), occupied 30% of the vegetated intertidal zone by the 2000s. Although waterbird species richness did not change between the 1980s (110) and the 2000s (111), 13 species found in 1980s were replaced by 14 newly recorded species. Moreover, there were more species with declining trends (58) than with increasing trends (19). The population trends of species were affected by residential status and habitat types. Transients, wintering migrants, and habitat specialists were more likely to show declining trends compared to those breeding at Dongtan (including year-round and summer residents) and habitat generalists. Furthermore, species associated mainly with natural wetlands were more likely to decline than those associated mainly with artificial wetlands. These patterns suggest that the loss and change of wetland habitats at Chongming Dongtan adversely affected local population dynamics and might have contributed to the global decline of some waterbird species. Because Chongming Dongtan provides stopover and wintering habitats for many migratory waterbirds, protection and restoration of natural wetlands at Chongming Dongtan are urgently needed.

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    • "The invasion of S. alterniflora has also caused a decline in the species richness and biomass of macrobenthic communities (Wang et al., 2010). As a consequence, the shorebird populations in the coastal wetlands could be seriously threatened (Ma et al., 2009). Therefore, control of this invasive plant Spartina alterniflora , especially in wetland nature reserves, is both important and necessary for successful biodiversity conservation. "

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    • "The human-related destruction of these habitats and rising global temperatures have become the principal contributors to the loss of fifty per cent of all the world's wetlands since 1900 (Finlayson and Davidson 1999). Similarly, partially as a consequence of habitat loss, the global waterbird population has decreased by 44 % in the few past years alone (Delany et al. 2010) and numerous studies have reported notable declines in waterbirds on a local scale (Crowe et al. 2008; Ma et al. 2009; Sandilyan et al. 2010). However, very little is known about the part played by invasive species in this decline, with the exception of the well-documented role of predatory alien mammals such as, for instance, the American mink Neovison vison (Nordström et al. 2002; Brzezin´ski et al. 2012) or the raccoon Procyon lotor (Ellis et al. 2007). "
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    • "Since its intentional introduction to China in 1979 for erosion control and seawall protection, cordgrass has spread along the coasts through natural dispersal and intentional introductions. Occupying a total area of 34 500 ha as of 2007, cordgrass is a dominant plant in the salt marsh in east China (Wang et al. 2006; Ma et al. 2009). By replacing native plants and forming a dense monoculture and reed–cordgrass mixture, cordgrass has altered the habitat structure and food resources for birds, leading to a decrease in bird diversity in the invaded areas (Gan et al. 2009, 2010; Ma et al. 2011). "
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