Optimal scale landscape ecological risk evaluation based on the SI-ERI model: A case study of Leshan City, Southwest China

Scale effects and evaluation models are crucial to the accuracy of landscape ecological risk evaluation. However, most studies conduct these evaluations at a single scale or with a single model, ignoring potential scale effects and changes in landscape patterns. To address this, we took the Leshan City in Sichuan Province of China as a study case. We determined that the optimal spatial granularity for the study area is 150 m by analyzing the sensitivities of eight landscape pattern indices such as landscape fragmentation, landscape spreading, and Shannon’s diversity at different spatial granularities, and employing the inflection point identification method. Building on this, we constructed a landscape pattern index model (ERI model) and a landscape pattern index model coupled with the ecological process of soil erosion (SI-ERI model) by incorporating the natural geographic factors of the study area. We used the ERI and SI-ERI models to evaluate the landscape ecological risk of Leshan City across multiple scales, including ecological, administrative, and sample scales. After conducting overlay and spatial autocorrelation analyses of the multi-scale evaluation results, we determined that the administrative scale is optimal for evaluating landscape ecological risk in the study area. At this scale, we verified the accuracy and reliability of the two models’ evaluation results against the actual ecological environment in typical areas within the study area. The findings indicated that the SI-ERI model provided more precise and accurate spatial characterization, effectively reflecting the actual landscape ecological risk of Leshan City. According to the SI-ERI model’s evaluation results at the administrative scale, Leshan City’s overall risk level is relatively low, with good ecological environmental quality. Low-risk areas constitute 56.16% and medium-low-risk areas make up 23.81%, aligning closely with the city’s actual situation. This study thus offers a scientific basis and theoretical reference for managing ecological risks and planning urban development in Leshan City.