Evaluating the spatiotemporal land ecological changes in the Yangtze-to-Huaihe Water Diversion Project area

As a fundamental component of human existence, land is inextricably linked to human development, and its ecological functions are closely associated with multiple sustainable development goals. This paper presents a framework for constructing and optimizing ecological function space, with the Yangtze-to-Huaihe Water Diversion Project area serving as a case study. A comprehensive land ecological index system is established, encompassing natural foundation, land degradation, land production, ecological structure, and ecological protection. An identity-discrepancy-contrary connection method is employed to investigate changes in regional land ecological functions before (2013) and during (2017, 2020, and 2022) the project's construction based on remote sensing data. The results indicated that the mean values of the land ecological index for each period were 0.1883, 0.1981, 0.2253, and 0.1370, respectively. The study calculated the connection, differences, and contradictions in the land ecological impacts across the counties, revealing a gradual decrease in differences and a growing prominence of contradictions. The land ecology of the Yangtze-to-Huaihe Water Diversion Project area is affected by the project construction, particularly within the construction area, showing an overall improvement. Most counties exhibited a trend of ecological improvement compared to the land ecology before the project's construction. However, after the project implementation, most districts demonstrated a trend of ecological deterioration. As the distance from the construction canal increases, the characteristics of each section and stage vary, generally exhibiting an exponential decrease in the land ecological index. The study highlighted the significance of enhancing the land ecological pattern, improving water quality, increasing water supply along the project, and alleviating groundwater overexploitation. The study can serve as a reference for land ecological protection and restoration in water transfer areas and river basins worldwide.