## 4 Discussion
### Limitations and Future Research Prospects  
The spatiotemporal distribution of ecological quality obtained in our study aligns with previous research [119], establishing a reliable method for assessing changes in Ecological Quality Index (EQI) within the three major urban agglomerations. This study reveals significant spatial heterogeneity in ecological environmental quality and identifies ecological hotspots that need protection and monitoring within the context of urban expansion. Despite these findings, it is important to acknowledge the limitations of our research. Firstly, changes in ecological quality are influenced by various factors, making  
Figure 12: LISA cluster map of EQI in three urban agglomerations in 2001 and 2020. (**a–c**) Clustering patterns of EQI in 2001 of BTH, CYRD, and PRD, respectively. (**d–f**) Clustering patterns of EQI in 2020 of BTH, CYRD, and PRD, respectively.  
it challenging to provide a comprehensive explanation of ecological quality distribution and influence pathways using limited indicators [120]. Especially for complex systems like cities, it would be more reasonable to quantify the relationship between urban scale and ecological quality changes by considering factors such as population size, land expansion, and management policies [88]. Secondly, the study focused on EQI for two specific years, 2001 and 2020. However, a more refined analysis of the temporal distribution would enhance our understanding of the driving factors behind EQI changes by introducing panel regression analysis after constructing a long panel [121]. Even strong seasonal variations in climate and vegetation factors should be considered, because vegetation activities and phenological changes can also affect local climate by regulating the surface energy budget [122]. Additionally, we can explore the excellent performance of spatial econometric models such as Spatial Durbin Model (SDM) to analyze variables' influence on ecological quality and estimate their trend.  
Therefore, future studies should aim to investigate shorter time interval data to capture the dynamics of ecological quality over time, even on a seasonal scale utilizing some spatial econometric models. Moreover, incorporating more comprehensive indicators that encompass both human activities and natural factors may be a more scientific solution to evaluating ecological quality in cities. Despite these limitations, the proposed \"FIPS\" framework has shown stable and good performance in large-scale ecological quality tasks, and the introduction of multi-level and more scientific indicators also provides a foundation for the popularization and promotion of the framework. More importantly, this study provides a feasible method to maintain the balance between ecological and economic development in urban areas and establishes an ecological quality monitoring network. Simultaneously, by combining the distribution of protected areas, ecological redline and ecosystem services, it is possible to analyze existing imbalances in urban planning and ecological management to provide targeted and sustainable management recommendations for improving regional ecological quality [123].