Human negative, positive, and net influences on an estuarine area with intensive human activity based on land covers and ecological indices: An empirical study in Chongming Island, China

Human activities have widely spread over nearly every corner of the world and been remarkably influencing the natural ecosystem since the 20th century. Identifying and quantifying the negative and positive influences of human activities are important for providing a solid basis for reasonable exploitation and effective conservation. This study focused on the negative and positive influences of human activities on five “macro to micro” aspects of an estuarine ecosystem, including island geomorphology, landscape pattern, plant community, physical quality, and chemical environment. An evaluation model was established using spatiotemporal ecological information from remote sensing, and three new indices, namely, human damage index (HDI), human regulation index (HRI), and human net influence index (HNII), were established to quantify the negative, positive, and net influences of human activities, respectively. Chongming Island in the Yangtze River Estuary of China was used as the study area, and four scenes of remote sensing images in 1988, 1995, 2007, and 2017 served as the data source. Results indicated that HDI initially increased and then decreased, HRI showed generally increasing characteristics, and HNII initially decreased and then increased in the entire study area from 1988 to 2017. Although the net influence was negative, ecological conservation and management since the 21 st century have clearly increased the HNII. Wetland vegetation, mudflat, and woodland had positive HNII; farmland, water area, and pond had HNII close to zero; and building, traffic, and industrial lands possessed negative HNII. The model was proven to greatly contribute to judging the ecological efficiencies of different types of land uses and optimizing the spatial configuration of human activities in estuarine areas.