## 3 Results
### Spatiotemporal Change Analysis of Landscape Ecological Risk in Sichuan Province
#### 3.2.2 Spatial Changes in Landscape Ecological Risk  
During the designated study period, landscape ecological risk in Sichuan Province revealed a pattern characterized by high risk in the western region and low risk in the eastern region (Figure 4). Compared to 2005, there was a slight increase in medium-risk, higher-risk, and highest-risk areas in 2010; furthermore, the area of lowest risk transformed into a lower-risk area and the medium-risk area became larger, while the area of medium risk transformed into a higher-risk area, and the risk was developing towards an increasing trend. Compared to 2010, there was an increase in medium-risk, higher-risk, and highest-risk areas in the original region in 2015. The risk shows a steady growth trend; only a few lower-risk areas were converted to medium-risk areas. Compared to 2015, the landscape ecological risk situation in 2018 increased significantly, especially in the transformation of medium-risk areas into higher-risk and highest-risk areas, which was primarily observed in the Ngawa Tibetan and Qiang Autonomous Prefecture, the Ganze Tibetan Autonomous Prefecture, and the central urban area of Chengdu. These findings emphasize the rapid expansion of landscape ecological risk areas and a heightened severity of risk distribution during this period, posing a substantial threat to the ecological security of Western Sichuan and the Chengdu Plain. Figure 5: The risk area and proportion of each level in Sichuan Province from 2005 to 2018. The displacement of the risk center of gravity serves as a valuable indicator for understanding the spatial distribution, direction, and potential trajectory of risk. When attempting to intuitively depict the spatial characteristics and trends of elements, the utilization of the standard deviation ellipse is highly effective [29]. In this study, we employed landscape ecological risk grades as the focus of analysis and conducted an investigation utilizing the standard deviation ellipse tool available in ArcGIS 10.2, allowing us to obtain the results regarding the center-of-gravity migration characteristics shown in Figure 7.  
During the process of each risk grade's center-of-gravity migration, a distinct pattern of high-grade risk emergence from west to east was exhibited. Analyzing the spatial trajectory of the center-of-gravity movement during four periods, it can be noted that the center of gravity of the lowest risk grade was primarily concentrated on the boundary between Chengdu and Ziyang; it shifted towards the southwest, then proceeded to the north, and finally relocated to the southwest again. The center of gravity of lower risk predominantly resided in the western region of Chengdu and the northwestern region of Ya'an. It followed a trajectory of northeastward movement initially; then, it moved to the east and ultimately moved to the west. The center of gravity of medium risk was concentrated around the boundary of Ganze Tibetan Autonomous Prefecture and Ngawa Tibetan and Qiang Autonomous Prefecture, moving to the east at first, then moving to the west, and finally moving to the east. The center of gravity of higher risk was concentrated in Ganze Tibetan Autonomous Prefecture, moving to the west at first and then moving to the east. The center of gravity of highest risk was predominantly located in Ganze  
Figure 6: Changes in risk transfer at different levels from 2005 to 2018. Tibetan Autonomous Prefecture and Chengdu, with a consistent westward trajectory of risk migration. From the perspective of azimuth angle change during the four periods, it can be noted that the lowest-risk area exhibits a'southwest-northeast' pattern. Additionally, the azimuth angle demonstrated a continuous increase, indicating the gradual stabilization of the'southwest-northeast' directional pattern. Conversely, the pattern for the lower-risk area underwent more drastic changes.