Rapid Loss of Tidal Flats in the Yangtze River Delta since 1974

Xing Li, Xin Zhang, Chuanyin Qiu, Yuanqiang Duan, Shu’an Liu, Dan Chen, Lianpeng Zhang and Changming Zhu
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Xing Li: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
Xin Zhang: State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China
Chuanyin Qiu: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
Yuanqiang Duan: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
Shu’an Liu: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
Dan Chen: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
Lianpeng Zhang: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China
Changming Zhu: School of Geography, Geomatics and Planning, Jiangsu Normal University, Xuzhou 221116, China

IJERPH, 2020, vol. 17, issue 5, 1-20

Abstract: As the home to national nature reserves and a Ramsar wetland, the tidal flats of the Yangtze River Delta are of great significance for ecological security, at both the local and global scales. However, a comprehensive understanding of the spatiotemporal conditions of the tidal flats in the Yangtze River Delta remains lacking. Here, we propose using remote sensing to obtain a detailed spatiotemporal profile of the tidal flats, using all available Landsat images from 1974 to 2018 with the help of the Google Earth Engine cloud platform. In addition, reclamation data were manually extracted from time series Landsat images for the same period. We found that approximately 40.0% (34.9–43.1%) of the tidal flats in the study area have been lost since 1980, the year in which the tidal flat area was maximal. The change in the tidal flat areas was consistent with the change in the riverine sediment supply. We also found that the cumulative reclamation areas totaled 816.6 km 2 and 431.9 km 2 in the Yangtze estuary zone and along the Jiangsu coast, respectively, between 1974 and 2018. Because of reclamation, some areas (e.g., the Hengsha eastern shoal and Pudong bank), which used to be quite rich, have lost most of their tidal flats. Currently, almost 70% of the remaining tidal flats are located in the shrinking branch (North Branch) and the two National Nature Reserves (Chongming Dongtan and Jiuduansha) in the Yangtze estuary zone. Consequently, the large-scale loss of tidal flats observed was primarily associated with reduced sediment supply and land reclamation at the time scale of the study. Because increasing demand for land and rising sea levels are expected in the future, immediate steps should be taken to prevent the further deterioration of this valuable ecosystem.

Keywords: Yangtze River Delta; tidal flat; remote sensing; Landsat; reclamation; sediment supply (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
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