Dynamic changes of wetland landscape in the coastal zone of Yancheng from 1990 to 2020 based on remote sensing images

Abstract:

Based on Landsat series satellite images, Google earth satellite images and object-oriented supervised classification method, the changes of coastal wetland landscape in Yancheng City, Jiangsu Province from 1990 to 2020 were analyzed on the basis of two-level classification of landscape. The results showed that:The total area of natural wetland landscape in Yancheng coastal zone showed a downward trend in the past 30 years, and the proportion of constructed wetland and non-wetland landscape area increased. The change trend of natural wetland area proportion in the study area was consistent with that in the partition, showing a trend of ‘decline-accelerated decline-slightly uplift’, and the change rate of intertidal mud beach was the highest. The proportion of intertidal saline marshes in the northern and southern Yancheng wetlands was 8.77% and 17.64%, respectively. The overall trend of coastal zone was ‘natural wetland-constructed wetland-non-wetland’. The wetland loss rate was the most significant from 2000 to 2010. The total area of wetland decreased by 360.27 km², and the average annual loss rate was as high as 1.29%. There were differences in the landscape transfer characteristics of Yancheng coastal zone in different periods. During 1990-2000, the landscape transfer directions of each wetland were relatively dispersed, and most of them were transferred within natural wetland or non-wetland. During 2000-2010, the transformation from tidal flat to aquaculture waters was dominant. During 2010-2020, cultivated land, rivers, woodlands and shallow waters all showed a trend of transformation to intertidal mud beaches. The most intense transformation trend of intertidal mud beaches, intertidal salt marsh waters and aquaculture waters was construction land. It is suggested that the main functions of natural wetlands in Yancheng coastal zone should be maintained with reasonable layout, planning and control of scale during the period of economic development.