## 3 Results Analysis
### Net Ecosystem Services Value  
From Table 8, we can see that the ESV in Ningde City demonstrated a downward trend, from CNY 85.07 \(\times\) 10\({}^{8}\) in 20 years, a decrease of 7.69%, which indicated that the ecosystem structure of Ningde is fragile. It is worth noting that the dominant land-use types in Ningde's ESV are forest land, water bodies, and orchard land, and the proportion of ESV in the total value fluctuates between 94.76% and 96.35%, indicating that these three land-use types play an extremely vital role in the ecological function of Ningde City. Among them, forest land provides the highest value of ecosystem services of all land-use types and has been in a leading position during the whole research period; however, its ESV has generally decreased over the past 20 years from CNY 890.95 \(\times\) 10\({}^{8}\) in 2000 to CNY 786.70 \(\times\) 10\({}^{8}\) in 2020, with a decrease of 11.7%. On the other hand, the ESV of grassland decreased gradually from 2000 to 2020, mainly due to its decreasing area. Additionally, the percentage of ESV in orchard land and water bodies increased continuously, while the percentage of ESV for unutilized land was the smallest, which indicated that the change in ESV of unutilized land had little influence on the total ESV. It can also be observed from Table 8 that ESV in Ningde City showed different trends in different stages. From 2000 to 2010, with the exception of unutilized land, the ESV of cultivated land and forest land changed greatly, while that of orchard land changed the least. Contrary to the previous stage, the ESV of all land-types illustrated a positive change from 2010 to 2020, but the overall increase was not large, with a range of less than 3%. In general, forest land and water bodies contributed the most to total ESV, followed by grassland and cultivated land, which indicated that the evolution of land-use pattern in Ningde City has a direct and significant influence on ESV. It was observed that the sub-type of ESV in Ningde City displayed a downward trend in the fluctuation during 2000-2020 (Table 9). Among them, food production's ESV descended at the fastest rate, with a declining rate of 14.99%; followed by the maintaining nutrient cycle, with the change rate of \(-\)13.23%, which was mainly due to the direct \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **Year** & **Cultivated Land** & **Forest Land** & **Orchard Land** & **Grassland** & **Water Bodies** & **Unutilized Land** & **Total** \\ \hline \multirow{3}{*}{ESV/10\({}^{8}\)} & 2000 & 26.13 & 890.95 & 74.65 & 31.74 & 82.05 & 0.02 & 1105.54 \\  & 2010 & 21.14 & 739.73 & 64.43 & 21.57 & 85.09 & 0.04 & 932.00 \\ \cline{1-1}  & 2020 & 18.70 & 786.70 & 71.19 & 18.50 & 125.32 & 0.07 & 1020.47 \\ \hline \multirow{3}{*}{Change rate/\%} & 2000–2010 & \(-\)0.19 & \(-\)0.17 & \(-\)0.14 & \(-\)0.32 & 0.04 & 0.67 & \(-\)0.16 \\  & 2010–2020 & \(-\)0.12 & 0.06 & 0.10 & \(-\)0.14 & 0.47 & 0.82 & 0.09 \\ \cline{1-1}  & 2000–2020 & \(-\)0.28 & \(-\)0.12 & \(-\)0.05 & \(-\)0.42 & 0.53 & 2.05 & \(-\)0.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Ecosystem services value in Ningde City from 2000 to 2020.  
relationship between the reduction in forest land area with a larger value coefficient. The decreasing trends of the ESV for aesthetic landscape, climate regulation, and biodiversity were relatively slow, while purifying the environment was the slowest of all ecological services, with a decline of \(-9.83\%\). Furthermore, climate regulation, hydrological regulation, and soil conservation were the main parts of ecosystem services in Ningde City, accounting for more than 61.53% of the total value; however, the ESV of the water supply only accounted for 0.78% of the total ESV.