Study on the Spatiotemporal Changes and Driving Factors of Habitat Quality in the Yarlung Zangbo River from 2000 to 2020

The Yarlung Zangbo River (YLZB), the world's highest-altitude and longest plateau river, its highly vulnerable to global climate change due to its delicate ecological environment. Understanding the changes in habitat quality and their driving factors in the YLZB is crucial for ecological conservation and sustainable development in the region. In this study, we analyze land use data from 2000 to 2020, using land use transfer matrix, habitat quality model, optimal parameter geographic detectors, correlation analysis, and partial least squares structural equation model(PLS-SEM) to explore the spatiotemporal changes in habitat quality in the YLZB from 2000 to 2020. It also quantitatively analyzes the mechanisms driving the differentiation in habitat quality. We also examined the relationships between various driving factors affecting habitat quality differentiation within the basin. The results show that: 1) Forests, grasslands, and unused land cover 94.14% of the basin area. Significant land use changes occurred between 2005 and 2010, with an increase in unused land, forest land, and water bodies, while grasslands, permanent glaciers, and snowfields decreased continuously. 2) The average habitat quality in the YLZB declined from 0.59 to 0.54 between 2000 and 2020, indicating an overall downward trend. Habitat quality patches became more fragmented and diverse, with the most significant decline observed from 2005 to 2010. 3) Habitat quality is higher in the southeast and lower in the west of the study area. From 2000 to 2020, the degraded regions covered a significantly larger area compared to the improved regions. Improved regions, accounting for 17.78% of the area, were mainly concentrated in small basins such as Duoxiong Zangbu and Palong Zangbu. Degraded regions made up 20.48% of the area, and were primarily located in the middle and upper reaches of the YLZB, including counties like Zhongba and cities like Shigatse. 4) NDVI(Normalized Difference Vegetation Index), elevation, and annual average temperature are key factors affecting changes in habitat quality along the YLZB. Elevation indirectly impacts NDVI through its influence on climate conditions, which in turn leads to a decrease in habitat quality. Our study highlights the importance of considering land use changes, such as the conversion of grasslands and the loss of glaciers, in developing effective ecological protection strategies for the YLZB. These findings contribute to a better understanding of the ecological dynamics within the basin and provide valuable insights for sustainable management and conservation efforts.