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The key ecological functional zone plays a significant role in maintaining ecosystem security, water conservation function and environmental protection. However, owing to rapid industrialization and urbanization, some ecological functional zones have undergone great changes in land use, which has changed the landscape pattern characteristics and resulted in ecological risks, affecting the regional ecological environment and water security. In this study, the core water source area of the Middle Route of China’s South–to–North Water Diversion Project is selected as the case study. A regional landscape ecological risk index (ERI) was constructed to evaluate the landscape ecological risk driven by land use transformation. Moreover, the ERI's spatiotemporal characteristics were investigated using a combination of geographic information systems and geostatistical techniques, which reveal the dominant land use function types associated with ecological risks and their causes. We found that (1) there was not a notable shift in land use, and the level of ecological risk increased slightly from 2010 to 2015. The conversion of previously unproductive land into places for industrial production land and agricultural productive land played a significant role in this phenomenon. From 2015 to 2020, the Danjiangkou Reservoir officially started operation. Furthermore, the improvement of residents’ awareness of environmental protection and natural forest land significantly reduced the ecological risk. (2) The ecological risk has a strong positive autocorrelation, exhibiting a pattern of high in the east and center, low in the west and periphery. (3) An obvious corresponding relation exists between the impacts of topography, soil, and climate on patterns of land use and ecological risk. Additionally, the strict ecological protection policies implemented by the Chinese government have realized remarkable achievements in promoting the improvement of ecological risks. Our study can provide a decision–making basis for the local authorities to conduct ecological risk prevention activities and ensure the sustainable northward flow of clean water.

Plant DNA from sediments (sedDNA) are increasingly used to reconstruct the past vegetation composition, which contrasts with the few investigations on the relationship between the plant sedDNA signal and modern vegetation. Here, we applied broad-scale terrestrial plant sedDNA metabarcoding on surface sediments from 201 lakes in eastern and northern Asia to discuss the applicability as well as the limitations of using plant sedDNA metabarcoding for palaeovegetation studies. In total, 381 terrestrial plant taxa were determined with the universal plant primers of trnL g and h. Overall, plant sedDNA approach is able to retrieve major vegetation signals. The composition of plant sedDNA reflect well the vegetation types and related climate characteristics, and it also signals which are the dominant taxa in the vegetation. Our results indicate that plant sedDNA metabarcoding could be a reliable proxy of vegetation composition at a sub-continental scale and along large environmental gradients. But certain drawbacks such as limited taxonomic resolution, biases in the relative abundance of taxa, and a generally high variability of samples from similar vegetation types need to be solved before it can be widely applied to reconstruct palaeofloras.