Coastal Wetlands in the Changjiang Estuary

Abstract

The enormous quantities of sediment produced by the Changjiang (Yangtze River) have created extensive coastal wetlands in the estuarine region, which have been colonized by various types of salt marsh vegetation. As the Changjiang Estuary is located adjacent to the megacity of Shanghai, human activities exert substantial pressures on the coastal wetlands and cause coastal ecosystem degeneration and consequent decreases or loss in ecosystem services. The major stresses from human activities on the coastal wetlands in the Changjiang Estuary include urbanization, reclamation, the introduction of invasive species, overfishing, and environmental pollution. In this chapter, the succession of plant communities in the coastal wetlands of the Changjiang Estuary is described. The spatial and temporal variation of plant communities on salt marshes are analyzed on the basis of remote sensing (RS) and mapping, combined with field inventories of sampling plots. The population expansion of an exotic species, Spartina alterniflora, after its introduction to the coastal wetlands in the Changjiang Estuary in the 1990s, is described and analyzed. The impacts of the invasion of S. alterniflara on benthic communities are examined along intertidal salt marsh gradients, and the invasion history is described. A cellular automaton (CA) model was developed to simulate the expansion of S. alterniflora and to study the interactions between the spatial pattern of expansion and salt marsh vegetation ecosystems. Field experiments and a demonstration project were carried out to control the invasion of S. alterniflora. Finally, this chapter discusses the future development, management, and conservation of coastal wetlands and biodiversity in the Changjiang Estuary.