Assessing wetland ecological quality and protection effectiveness in the Qilihai Wetland using long-term multi-source remote sensing data

Understanding the long-term evolution of wetland ecological quality is crucial for assessing the effectiveness of protection strategies. In this study, multi-source remote sensing data were used to evaluate the ecological quality and protection effectiveness in the Qilihai Wetland in China. First, Landsat data spanning from 1984 to 2023 were employed to calculate the Remote Sensing Ecological Index (RSEI) to assess wetland ecological quality during three distinct periods: natural state, development, and conservation. Prior to 2011, RSEI exhibited notable fluctuations, indicating that ecological quality changed significantly. RSEI values declined significantly from 2012, reaching 0.74 by 2017. The implementation of wetland conservation measures in 2017 led to a significant improvement in ecological quality. Furthermore, a dual-temporal land cover classification method was developed using GF and ZY3 satellite imagery from 2016 to 2023, enabling a detailed examination of land cover dynamics under conservation efforts. The results indicated a significant increase in vegetation diversity, evidenced by the large-scale emergence of Typha orientalis, Nelumbo nucifera Gaertn, and Nymphoides peltata. And the total vegetation area expanding from 24.47 km2 in 2016 to 30.71 km2 in 2023. Furthermore, the analysis of wetland vegetation area, water body area, and RSEI changes demonstrated the effectiveness of vegetation replanting in improving ecological quality. The optimal water body area for sustaining the best ecological quality was determined to be 8–10 km2. Based on these findings, we provided recommendations for future vegetation replanting aimed at improving ecological quality and minimizing conservation costs. These methods provide a significant reference for other wetlands globally and contribute to the development of effective wetland protection strategies.