| Shanghai, with the huge amount of the silt brought by the Yangtze River, is blessed with plentiful coastal tidal marshes, which are the potential land resources for economical development. The tidal marshes could also provide ecological service and environmental value, such as improving water quality, mitigating climate change and conserving biodiversity. The results of this research on the developmental dynamics of the tidal marshes in Shanghai provide a sound basis for resource management and planning, preservation of biodiversity, sustainable development and utility of wetlands in the region.Remote sensing analysis with Landsat TM/ETM+data as well as field surveys were carried out in this study to explore the developmental dynamics of the tidal marshes in the past 20 years. The author evaluated the tidal marshes ecosystem services value dynamically, analyzed the sensitivity and the health of the tidal marshes, discussed the influencing factors of the Yangtze estuary tidal changes, and put forward the strategies for the management of tidal marshes. The results of this study showed:(1) The tidal marshes are silting up on the whole, but they are growing more slowly in the recent years, however, Jiuduansha Shoal's shape remains stable. The main silting up areas are the mainland, the east of the islands, the north and the shoal. Nevertheless, the tidal marshes are not expanded year by year. The various types of tidal marshes are declining except for S. alterniflora. In the last 20 years, the tidal marshes were relatively seriously enclosed, with a cumulative enclosure of 653.54 km2, and the main enclosed areas are:Chongming Dongtan and Chongming Beitan, Nanhui Dongtan, Hengsha Dongtan, Changxing island west bank.(2) Overall, in recent 20 years, Shanghai tidal marshes ecosystem service value displays an obvious downward trend, and the various types of the tidal marshes ecosystem service value showed a marked decline apart from S. alterniflora. This is because various types of tidal marshes are tending to decline. From the point of view of all kinds of tidal marshes ecosystem service value, Guangtan service functions most efficiently, followed by P. australis and Scirpus mariqueter, and S. alterniflora has soared, from scratch fast. From the regional perspective, the tidal marshes ecosystem service value showed a reduced tendency, except Jiuduansha Shoal, Chongming Xitan, Dongfengxisha Shoal and Qingcaosha Shoal. S. alterniflora intrusion and the tidal marshes'slow growth in recent years are the main reasons for reducing the 2009 ecosystem service value.(3) Chongming Dongtan, Jiuduansha Shoal, and Nanhui Dongtan are the highest ecological sensitive areas, Dongfengxisha Shoal, Qingcaosha Shoal, Zhongyangsha Shoal, Baoshan beach and Chongming Beitan are the higher ecological ecological sensitive areas, and the ecological sensitivity of HengSha Dongtan, Chongming Beitan, Pudong beach, Hangzhou bay beach is relatively weak. Caused by over-development and the absence of effective management and protection, the tidal marshes in mainland are suffering from severe degeneration and poor health state. Scientific management and conservation of islands and Shoal in Yangtze estuary is enhanced under appropriate development, therefore, the tidal marshes in good health.(4) The tidal marshes are facing many threats, such as enclosure, economic activity, biological invasion, pollution, upstream, large-scale water conservancy projects and climate change. Therefore better management and protection are needed. The author suggested a principle of the integration of the dynamic protection and dynamic development; a goal to retrieve the migratory birds'populations; a bottom line with the area of the tidal marshes not reduced due to the human factors. What's more, the author suggested that the monitoring of the ecological environmental quality be strengthened with high-quality legal system construction and mechanism construction; and the control and management of the biological intrusion be reinforced, and consequently, the tidal marshes exploitation and utilization be on the path of the sustainable development.
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