[Ecological Environment of the Haihe River Basin in Response to Meteorological Drought and Human Activities]

With the intensification of climate change and the implementation of ecological engineering， it is crucial to study how the ecological environment responds to meteorological drought and human activities. Currently， relevant research is largely limited to single-element indicators such as the normalized difference vegetation index （NDVI） and gross primary productivity （GPP）. However， the ecological environment consists of multiple elements， and there is still a lack of further research on the response differences between the improved remote sensing ecological index （IRSEI） that integrates multiple elements and other indices. Therefore， the Haihe River Basin， a typical region， has been selected as the study area. First， the Sen+Mann-Kendall trend analysis method was employed to analyze the changing trends of ecological environment assessment indicators such as NDVI， GPP， and IRSEI from 2001 to 2020. Then， combined with data such as the standardized precipitation evapotranspiration index （SPEI）， Pearson correlation analysis and the NRBO-XGBoost model were used to explore the responses of different ecological environment assessment indices to meteorological drought and human activities. The results indicated that： ① Compared to the traditional RSEI， IRSEI had clear advantages in the Haihe River Basin， effectively comparing interannual differences and highlighting changes in the ecological environment over long periods. ② NDVI， GPP， and IRSEI showed upward trends in 85.72%， 94.32%， and 78.77% of the areas， respectively， with many located in the western and northern mountainous regions of the basin and in the plateaus in the northwest. ③ The ecological environment showed significant differences in response to meteorological drought across different seasons， with the most obvious positive and negative responses in summer and winter， respectively； the response to spring and autumn meteorological droughts was relatively weak. ④ The impact of human activities on ecological environment changes was significant， with the degree of improvement from human activities ranked as follows： grasslands > forests > shrubs > cropland > impermeable surfaces， in which impermeable surfaces exhibited both improvement and degradation characteristics. The research findings can provide decision-making references for the ecological environment protection and sustainable development of the Haihe River Basin.