# Historical Eco-Environmental Quality Mapping in China with Multi-Source Data Fusion
## 3 Results
### EEQ of Major Cities  
Beijing, Shanghai, Guangzhou and Nanjing are important cities in China. Beijing is the capital of China and the political, cultural and diplomatic center of the country. Shanghai is the economic center of China and the frontier of reform and opening up [52]. Nanjing is the capital city of Jiangsu Province, known as the ancient capital of the Six Dynasties and an important national transportation hub [53]. Guangzhou is the capital city of Guangdong Province, a national mega-city, an important port for foreign exchanges, and a center of gravity for international trade [54]. The rapid economic and social development of the four major cities has also driven the development of the surrounding cities, and the Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta regions are all using these four cities to maintain linkage development. Since the twenty-first century, ecological and environmental problems in the Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta regions have been a hot topic [55], and it has become particularly important to use scientific and objective methods to study the EEQ of these regions in a long time series, which is very important for the governments in the region to formulate ecological protection. Based on the 2000, 2008 and 2017 M-RSEQI indices, 30m impervious surface data from Tsinghua University and Google historical images, the coupling pattern between EEQ and impervious surface was investigated in Beijing, Shanghai, Guangzhou, and Nanjing. In Figures 11-14, it can be seen that Guangzhou had the best overall EEQ, followed by Beijing, and Nanjing and Shanghai have poorer EEQ. Specifically, the EEQ of Shanghai was the worst. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Level** & **Area (10,000 \(\times\) km\({}^{2}\))** & **Percentage (\%)** \\ \hline M-RSEQI Reduced & 1.00 & 0.86 \\ M-RSEQI Unchanged & 87.94 & 74.80 \\ M-RSEQI Improvement & 28.61 & 24.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Change area of M-RSEQI in the Yellow River Basin from 2000 to 2017. Figure 10: Change map of M-RSEQI in the Yellow River Basin from 2000 to 2017. Beijing, Shanghai, Guangzhou, and Nanjing are significant cities in China. Beijing serves as the capital and acts as the political, cultural, and diplomatic center of the country. Shanghai holds the role of China's economic hub and stands at the forefront of reform and opening up policies [51]. Nanjing, known as the ancient capital of the Six Dynasties, serves as the capital city of Jiangsu Province and plays a crucial role as a national transportation hub [52]. Similarly, Guangzhou, the capital city of Guangdong Province, holds the status of a national mega-city, serves as a prominent port for foreign exchanges, and acts as a center for international trade [53]. The rapid economic and social development of these four major cities has had a significant impact on the surrounding areas. The Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta regions all utilize these cities to drive and maintain interconnected development. Ecological and environmental issues in these regions have become a prominent topic since the 21 st century [54]. Therefore, it is crucial to understand the role of the city in the country. Figure 11: M-RSEQI, impervious area (ISA) and Google historical images of Beijing in 2000, 2008 and 2017.  
to employ scientific and objective methods to study the long-term EEQ trends in these regions. This research is of great importance for regional governments in formulating effective ecological protection strategies. Using the 2000, 2008, and 2017 M-RSEQI indices, coupled with 30 m impervious surface data from Tsinghua University and historical images from Google, the relationship between EEQ and impervious surface was examined in Beijing, Shanghai, Guangzhou, and Nanjing. Figures 11-14 illustrate that Guangzhou exhibited the highest overall EEQ, followed by Beijing, while Nanjing and Shanghai had relatively poorer EEQ. Specifically, Shanghai had the lowest EEQ rating.