## 3 Results
### Dynamic Change in Ecological Environmental Quality in Jincheng City

Table 7: Monitoring changes in the level of the remote sensing ecological index in resource-based cities in 1990–2022. Figure 9: Images of the RCEI change monitoring in Jincheng. During 1990-1996, 81.6% of the regional ecological environmental quality in Jincheng City improved, primarily concentrated in the urban built-up area, the built-up area of Zezhou County, and the coal mining regions of Fenghuangshan, Ancient Mining, and Chengzhuang, which are located in the southern center of Jincheng City and displayed a concentrated area of improvement. From 1996 to 2002, the area of improved ecological quality decreased by 40%, while the total area of ecological degradation increased by 16.4%. From 2002 to 2006, the ecological quality improved significantly, and the percentage of ecologically restored area recovered to the level of 1990-1996, while the degraded area accounted for only 1.6%. From 2008 to 2013 and 2013 to 2018, the area of ecological improvement consecutively decreased, and the degraded area continued to rise, primarily concentrated in the northeastern part of Jincheng City. Feature classification showed that most of the ecologically degraded area comprised cropland and fallow land, as well as small- and medium-sized coal mine areas in and around the urban built-up area of Gaoping County. During 2013-2018, the area with no ecological change (level 0) accounted for the highest proportion of ecological change over the five-year period, reaching 69%. Between 2018 and 2022, Jincheng City witnessed a significant increase in ecological environmental quality, with 60.6% of the study area exhibiting mild improvement (level 1) and 2.7% achieving significant enhancement. The implementation of comprehensive ecological policies catalyzed substantial improvements in the ecological quality of urban built-up areas, coal mine production zones, and residential sectors across Jincheng City and its five counties and districts, attaining a significant level of improvement (+2 level). Conversely, the remaining 3.4% of areas experiencing ecological decline were primarily situated in Zezhou County, Yangcheng County, and Qinshui County, coinciding with the operational commencement of new coal mines. Over the seven analyzed periods, the proportion of areas undergoing ecological improvement exhibited a W-shaped pattern of fluctuation, while the proportion of degraded areas presented a contrasting M-shaped trend. The share of areas remaining unchanged was more volatile, displaying an inverted V shape, and experienced a sharp decline post-peak during the 2013-2022 interval, with variations ranging from 8.4% to 69%. Specifically, these unchanged areas were predominantly situated between degradation zones (depicted as red zones in Figure 9) and buffer zones surrounding improved green patches. They were centered around urban built-up locales, agricultural lands associated with coal mine production and habitation, fallow lands, and grassland regions. Throughout the entire study period (1990-2022), the proportions of improved, unchanged, and degraded areas were 86.3%, 4.7%, and 9%, respectively. Notably, areas that underwent significant degradation were mainly coal mining and built-up areas prior to 2018. Post-2018, the overall ecological quality showed marked improvement following the decommissioning of certain built-up and coal mining areas proximal to the city. In summary, the ecological quality of Jincheng City has displayed a pronounced upward trend.