Modified remote sensing ecological index (MRSEI) reveals spatiotemporal coupling of eco-environmental quality with traditional villages in Red River Basin

The Red River Basin (RRB) in Southwest China serves as a critical transboundary ecological barrier and a hotspot for multi-ethnic cultural heritage. Monitoring the spatiotemporal dynamics of eco-environmental quality (EEQ) is essential for regional sustainability. However, conventional remote sensing indices often suffer from spectral saturation and soil background interference in high-sediment basins and dry-hot valleys. To address these limitations, we developed a modified remote sensing ecological index (MRSEI) specifically tailored to the RRB. The MRSEI integrates the Soil-adjusted vegetation index (SAVI) and desertification monitoring index (DMI) to mitigate background radiation and capture surface sand exposure. Using Landsat time-series imagery from 2000 to 2025, combined with Sen's slope, Mann-Kendall trends tests, and OPGD, we quantified the long-term evolution of EEQ and analyzed its spatial coupling with 131 national-level traditional villages in the basin. Our results reveal three main findings. First, EEQ followed a V-shaped evolution trajectory, with the mean MRSEI declining from 0.45 (2000) to 0.42 (2010) before recovering to 0.58 (2025). driven by the transition from intensive agricultural expansion to ecological restoration policies. Second, we observed a significant spatial coupling exists between high-density village clusters and superior ecological zones (MRSEI >0.6), supporting the concept of “habitat-optimized” site selection rooted in traditional ecological knowledge. Third, natural factors, specifically slope and precipitation (q > 0.3), defined the ecological baseline, whereas the synergistic interaction between urbanization and gross domestic product (GDP; q = 0.43) emerged as the dominant anthropogenic stressor. Collectively, these findings clarify the biophysical basis of vernacular settlement adaptation and offer a quantitative framework for the integrated preservation of ecological security and cultural heritage in complex river systems worldwide.