Wetland changes before and after Baiyangdian ecological restoration project based on multi-source data and multi-feature combination

Objective Baiyangdian wetland is the largest wetland ecosystem in the North China Plain, and plays an important role in improving and regulating the climate and ecological environment of Xiong’an New Area and even the whole Beijing Tianjin Hebei Region. Exploring the changing characteristics of Baiyangdian wetland underlying surface before and after ecological restoration aims to provide theoretical reference for the subsequent ecological restoration project.

Method Sentinel-1 SAR images and Sentinel-2 multi-spectral images before and after ecological restoration (2017 and 2022) were selected to extract spectral index features, SAR index features and texture features. Combined with random forest method, the Baiyangdian wetland was classified, and the changes of Baiyangdian wetland before and after ecological restoration were analyzed from the changes of underlying surface type, area and landscape pattern index.

Result (1) The overall accuracy of classification using spectral index features, SAR index features and texture features was the highest. The importance contribution rates of spectral index features, SAR index features, and texture features were 40.713%, 27.269%, and 32.018%, respectively. (2) From 2017 to 2022, the area of cultivated land decreased significantly, while the area of wetland increased significantly. The increase of wetland area mainly comes from the conversion of cultivated land. (3) After ecological restoration, the fragmentation degree of forest land and water body in 2022 had a decreasing trend, and the aggregation degree and connectivity of water, emergent plants and forest had been improved to varying degrees, among which the most obvious was forest.

Conclusion The landscape of Baiyangdian wetland tends to be fragmented before the ecological restoration, while after ecological restoration, the connectivity and aggregation of water bodies, emergent plants, and forest land have been improved, which shows that the projects of returning farmland to lake, ecological dredging and water replenishment have increased the area of Baiyangdian wetland and improved the connectivity of water body.