Comprehensive evaluation of natural landscapes before and after earthquake based on GST-FAHP-GIS analytical method: A case study of Jiuzhaigou Nature Reserve, China

The Jiuzhaigou earthquake caused severe damage to its natural landscape. The seismic-induced changes in landscapes represent a complex and diverse process. In order to creatively assess the extent of earthquake-induced landscape destruction and study the focal points of landscape restoration, this study proposes a comprehensive framework system that integrates multiple indicators and methods to evaluate the impact of earthquakes on the Jiuzhaigou scenic area. In comparison to previous single-method studies, our framework system offers a more holistic explanation and predictive capacity regarding the trends and characteristics of post-earthquake landscape changes. Within this approach, we amalgamate Grey Statistical Technique (GST), Fuzzy Analytic Hierarchy Process (FAHP), Delphi Technique, and Geographic Information System (GIS). By selecting 24 landscape evaluation indicators, we establish five levels of landscape assessment, ranging from broad to fine-grained. Areas with higher visibility sensitivity are categorized as high visual sensitivity regions, indicating the need for focused restoration efforts. Based on the degree of landscape visual sensitivity, we introduce four visual sensitivity evaluation factors: slope gradient, slope aspect, relative distance, and vegetation coverage. The result demonstrates that the overall landscape grade of Jiuzhaigou decreased by 15% after the earthquake; the aesthetic indicator of the landscape within geological hazard experienced the greatest decline, decreasing by 73.3%, while the landscape's resilience indicator showed relatively minor changes. Notably, regions with high visual sensitivity exhibit a distinctive "Y"-shaped distribution pattern, with 56.8% of environmental hazard points possessing the highest visual sensitivity. The study also underscores the concentrated presence of geological hazard points and high visual sensitivity between the Nuorilang Waterfall and the scenic area entrance, necessitating prioritized restoration efforts in this zone. This research innovatively provides a method for assessing the damage caused by earthquakes to natural landscapes, and it holds significant guiding implications for relevant national decision-making bodies in policy formulation and implementation.