Three-Dimensional Coupling Assessment of Eco-Geological Environment in Alpine Gorge Areas Integrating the Remote Sensing Ecological Index, Ecosystem Services, and Geological Environment Carrying Capacity

Alpine gorge areas are typical regions where ecological fragility and geological hazard risk overlap strongly. Existing eco-geological assessments remain largely single- or dual-dimensional: remotely sensed indices describe surface status, ecosystem-service indices describe functional supply, and geological models are usually applied separately from ecological assessment, so each approach misses the information carried by the others. To close this gap, this study proposes a three-dimensional coupling framework for Eco-Geological Environment Carrying Capacity (EGECC) that integrates the Remote Sensing Ecological Index (RSEI), the Ecosystem Services Index (ESI) and the Geological Environmental Carrying Capacity (GECC), and applies it in Lixian County, Sichuan Province. The three indices were coupled at pixel level, and their coupling and vertical differentiation were analysed along an altitudinal gradient. Three findings are highlighted. (1) RSEI and ESI are only moderately correlated, and their altitudinal peaks are separated, so neither can substitute for the other. (2) GECC contributes the largest share of the variation in EGECC, indicating that the geological dimension carries information that is not a linear combination of the two ecological dimensions. (3) Consequently, the geological dimension cannot be reproduced from the ecological ones: degrading the framework to RSEI + ESI places part of the area in a lower class that the two-dimensional scheme would label as safe. A five-tier management strategy is outlined accordingly. The study provides a transferable basis for eco-geological zoning in alpine gorge counties.