Centennial-scale study on the spatial-temporal evolution of riparian wetlands in the Yangtze River of China

Abstract

• A classification system for riparian wetlands in the Yangtze River was build. • Spatial-temporal changes of riparian wetlands at centennial-scale was analyzed. • Riparian wetlands in the Yangtze River generally showed a decreasing trend. • Spatial-temporal changes of riparian wetlands can be divided into three stages. • Wetland protection policies have significant impacts, especially since 1998. Wetlands play a crucial role in maintaining the ecosystem function and ecological security of the Yangtze River. This study collected multi-source remote sensing image data, including historical topographic maps, Landsat, and Gaofen-2, and established a set of classification and interpretation standards for riparian wetlands in the Yangtze River. The artificial visual interpretation was used to reconstruct the spatial–temporal evolution process of riparian wetlands in the Yangtze River over the past century, clarified its characteristics, and analyzed the impact of climate change, damming, and land development and wetland policies. The results showed that: (1) Riparian wetlands in the Yangtze River generally showed a decreasing trend. Among them, those in the upper reaches showed a decreasing trend, those in the middle reaches increased during 1930–1980 s and decreased since the 1980 s, and those in the lower reaches fluctuated. (2) The spatial–temporal evolution can be divided into three characteristic areas. In the estuary (Shanghai and the coastal), riparian wetlands first decreased and then increased, and changed significantly. The three provinces in the downstream (Jiangsu, Anhui, and Jiangxi) and Chongqing showed a decreasing trend with great changes. The three provinces in the middle and upstream first increased and then decreased with little change. (3) The impact of wetland exploitation and protection policies can be divided into three stages: no wetland protection policies (before 1986), wetland protection policy development (1986–1998), and strict protection (1998–present). This study provides an important scientific foundation for the implementation of coordinated protection of the Yangtze River.