Due to the swift urban development and resulting human impact, a range of ecological and environmental issues have arisen, including forest land degradation, worsening living conditions, and destruction of the natural environment. Quantitative monitoring and comprehensive evaluation of regional ecological environment quality are crucial for assessing the sustainable development of cities(Ren et al,2017 and Xu,2013). Remote sensing technology facilitates rapid and accurate acquisition of natural elements that characterize the regional ecological environment, such as mountains, waters, and forests(Xie et al,2022 and Zhang et al,2020). Using remote sensing technology to assess the comprehensive environmental quality of Jiyuan City, the results of this evaluation offer a data reference for investigating and preserving urban ecological changes. Furthermore, these findings hold significant practical and decision-making value for the advancement of urban ecological civilization(Yan,2009).
Xu Hanqiu and colleagues developed the Remote Sensing Ecological Index (RSEI) for visualizing, analyzing, modeling, and predicting ecological conditions at a regional level(Xu,2013 and Xu,2013). Various types of RSEI have been proposed by researchers to cater to diverse geographical environments and ensure applicability. For instance, the Enhanced Remote Sensing Ecological Index (ERSEI) was developed to capture the unique features of arid zones. It encompasses a thorough analysis of the land surface characteristics and gradual shifts in water network influence(Zhang et al,2023, Sun et al,2023 and Hou et al,2016). For the Modified Remote Sensing Ecological Distance Index (MRSEDI) developed for the features of karst desertification, the Rocky Desertification Index (RI) is selected as a replacement for the heat index(Wang et al,2021 and Sun et al,2019). To avoid non-uniqueness in the eigenvector direction of the RSEI model, the causal analysis was performed using the Google Earth Engine platform(GEE) and Geographic detector(Feng et al,2022, Nong et al,2021, Wang et al,2023, Zheng et al,2022 and Jiang et al,2021).
However, in these remotely sensed ecological indices, the dryness index is selected as the mean of the sum of the Index-based Build-up Index(IBI) and the Soil Index(SI), which makes it difficult to highlight the impact of human activities. Changes in the SI depend on whether major geologic hazards or widespread anthropogenic impacts have occurred in the study area, whereas changes in the IBI focus on human changes in the size of building complexes. Comparing the two, the range of change of the IBI is much larger than that of the SI over the same period, and there may be a year in which the IBI is much larger than the SI, so the two indexes with different ranges of change should not be combined into a single index. In the process of evaluating the quality of ecological environment, human activities are a factor that cannot be ignored, and the influence becomes more and more obvious with the process of urbanization(Wang and Xu,2021). Therefore, this study tries to improve the original remote sensing ecological index and establish a separate sub-indicator to reflect human activities. One of the effects of urban development and human activities is the growth of building area, so the IBI was chosen to represent the dryness inde, and the Improved Remote Sensing Based Ecological Index (IRSEI) was used to evaluate and analyze the ecological environment of Jiyuan City from 2002 to 2021.The quality of Jiyuan City from 2002 to 2021 by using the IRSEI, which provides help and reference for future urban planning and ecological protection in Jiyuan City.