# Historical Eco-Environmental Quality Mapping in China with Multi-Source Data Fusion
## 3 Results
### Spatial and Temporal Changes in China's EEQ  
The spatial variations of the M-RSEQI trends in China from 2000 to 2017 are depicted in Figure 5 and Table 4. It is evident that the trends exhibit considerable diversity across different regions. The percentage of area where the M-RSEQI decreased and improved were 39.7% and 60.3%, respectively, indicating an overall improvement in EEG across most regions of China over the past eighteen years. Notably, regions experiencing a faster improvement in the M-RSEQI accounted for 9.19% of China's total area (slope \(\geq 2\times 10^{-3}\)a\({}^{-1}\)). These regions primarily include the Loess Plateau, Qinghai Province, Ningxia Hui Autonomous Region, and areas surrounding Sichuan Province. Conversely, the regions where the M-RSEQI decreased encompassed the Tarim Basin in Xinjiang, northwest Inner Mongolia, parts of southern Tibet, Yunnan Province, and the coastal areas of the Yangtze River Delta and Pearl River Delta. These regions exhibited a slow declining trend. Among the 35 provinces in China, including municipalities directly under the Central Government and Taiwan Province, 17 provinces displayed an increasing trend in the M-RSEQI, while 18 provinces exhibited a decreasing trend. Notably, the Ningxia Hui Autonomous Region had the fastest increasing speed (slope = 0.99 \(\times\) 10\({}^{-3}\)a\({}^{-1}\)), whereas the Hong Kong Special Administrative Region had the fastest decreasing speed (slope = \(-\)0.74 \(\times\) 10\({}^{-3}\)a\({}^{-1}\)). At the national level, the M-RSEQI showed a gradual improvement trend, albeit at a slow pace (slope = 0.18 \(\times\) 10\({}^{-3}\)a\({}^{-1}\)). In Figure 6, it can be seen that China's EEQ did not change much during 2000-2017, and the overall EEQ was low, with the average value of M-RSEQI below 0.3 in all years. The best EEQ in China during 2000-2017 was in 2007, when several policy documents were introduced to prepare for the Olympics [44]. For example, regulations such as the \"Opinions of the State Environmental Protection Administration on Further Strengthening Ecological Protection\" and \"Opinions on Strengthening Environmental Protection in Rural Areas\" were introduced. Local governments organized environmental protection efforts to strengthen the fight against ecological and environmental violations. Heilongjiang Province also increased the intensity of law enforcement inspections of straw burning, greatly reducing traffic congestion, air pollution and forest fires caused by straw burning  
Figure 3: Area (km\({}^{2}\)) of different EEG categories in China from 2000 to 2017.  
and other accidents [45]. In addition, the worst EEQ in China was in 2001 and 2015. In 2001, during the golden period of China's economic and social development, the provinces experienced rapid economic growth. At the same time, many EEQ problems arose. Severe acid rain pollution existed in southeastern China. Acid rain occurs in more than 90% of the 188 cities that fall within the acid rain control area [46]. In the report released by the National People's Congress on the completion of environmental protection in 2015, it was pointed out that the problems of heavy environmental pollution, high environmental risks and ecological damage were particularly prominent in the country this year, thus showing that the ecological and environmental situation in China was particularly severe in 2015. Figure 4: Spatial distribution pattern of M-RSEQI in China from 2000 to 2017. Figure 6 illustrates the stability of China's EEQ during the period 2000-2017, with a consistently low overall EEQ, indicated by the M-RSEQI average value remaining below 0.3 throughout the years. The highest EEQ in China was observed in 2007, coinciding with the implementation of various policy measures in preparation for the Olympics [44].