Exploring the ecological quality and its drivers based on annual remote sensing ecological index and multisource data in Northeast China

The remote sensing ecological index (RSEI) has been established as a comprehensive indicator to evaluating long-term ecological quality (EQ) changes. However, previous studies mostly focused on EQ change analysis at discrete time points and ignored the continuous process. This study aims to construct an annual EQ collection from 2000 to 2019 to reveal the spatial and temporal changes in EQ under the combined action of multiple factors. We developed annual RSEI in Northeast China based on Google Earth Engine and described the patterns of EQ changes from 2000 to 2019 using trend analysis. Furthermore, we quantified the contributions of natural and anthropogenic driving factors and their interactions on EQ changes utilizing the geographical detector model. The results showed that the EQ of Northeast China improved from Moderate to Good over 2000-2019, with RSEI increasing from 0.54 to 0.67. The pixel-based trend analysis suggested that the regions with stable and improved EQ accounted for 52.57% and 46.73%, respectively. EQ improvements were mostly found in cropland, grassland, and woodland. EQ deterioration areas only accounted for 0.70% and mainly occurred in urban, coastal, and sandy areas. Among the nine driving factors, elevation, land use intensity, and slope were the primary factors for EQ improvement, with contributions of 20%, 16%, and 13% in Northeast China, respectively, while the eco-engineering area explained 32% of the negative effect on EQ deterioration. Compared with the contribution of a single factor, the multi-factor interactions significantly enhanced those factors' explanatory power for EQ variations. The results of this study will provide significant information and important reference for decision-makers to make more targeted efforts on environmental protection and ecological restoration.