## 3 Results
### Ecosystem Services Value Change  
#### 3.3.1 Temporal Variation Characteristics  
The ESV of the study area showed an overall negative growth trend during the period over the 20-year period, decreasing from CNY 383.085 billion in 2000 to CNY 359.295 billion in 2020, with a total reduction of CNY 23.790 billion (Table 7). Notably, between 2015 and 2020, the ESV experienced a significant decrease, amounting to approximately CNY 23.627 billion, which accounts for 99.32% of the total reduction. There was a steady decline in the ESV for both arable and forest lands across the two-decade timeframe. Specifically, the ESV of farmland decreased by a total of CNY 13.236 billion, accounting for 55.64% of the total reduction, with a change rate of \(-\)17.72%. The continuous decline in the ESV of farmland indicates a trend of reduced farmland area and weakened ES functions of farmland. This is due to rapid urbanization and industrialization, which have led to the conversion of large amounts of farmland into built-up land, resulting in the erosion of agricultural production and related ES functions. The ESV of forest land decreased by a total of CNY 2.637 billion, representing 11.08% of the total reduction, with a change rate of \(-\)18.47%. Particularly after 2005, the decline became more significant due to the reduction in forest area, degradation of forest quality, and the conversion of some forest land into other land types, leading to a decline in forest ecosystem functions. The ESV of water bodies and grasslands initially rose before experiencing a subsequent decline. Overall, the ESV of water bodies and grassland decreased by CNY 7.91 billion and 0.008 billion. Notably, the reduction in the ESV of water bodies constituted 33.25% of the total reduction, with a change rate of \(-\)2.69%. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multicolumn{6}{c}{**Ku**} \\ \cline{2-8}  & **Farmland** & **Foresland** & **Grassland** & **Water Area** & **Unused** & **Built-Up** & **Lc** \\  & & & & & **Land** & **Land** & \\ \hline
2000–2010 & \(-\)1.36\% & \(-\)0.71\% & 70.42\% & 0.84\% & 24.80\% & 8.31\% & 1.88\% \\
2010–2020 & \(-\)0.47\% & \(-\)1.23\% & \(-\)9.68\% & \(-\)1.02\% & 0.41\% & 3.20\% & 1.10\% \\
2000–2020 & \(-\)0.89\% & \(-\)0.92\% & \(-\)3.72\% & \(-\)0.13\% & 13.12\% & 7.08\% & 1.33\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Land use dynamics degree. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Land Use**} & \multicolumn{6}{c}{**ESV (Billion CNY)**} & \multicolumn{3}{c}{**The Change in ESV**} & **Rate of** \\ \cline{2-7}  & **2000** & **2005** & **2010** & **2015** & **2020** & **2020(/Billion CNY)** & **Change/\%** \\ \hline Farmland & 74.698917 & 69.179083 & 64.504841 & 61.658279 & 61.462791 & \(-\)132.36126 & \(-\)17.72\% \\ Forest land & 14.276785 & 13.361057 & 13.267764 & 11.723055 & 11.64019 & \(-\)26.36595 & \(-\)18.47\% \\ Grass land & 0.01054 & 0.039086 & 0.084732 & 0.012539 & 0.002706 & \(-\)0.07834 & \(-\)74.33\% \\ Unused land & 0.00005 & 0.000016 & 0.000019 & 0.000022 & 0.00002 & 0.00015 & 300.00\% \\ Water area & 294.099019 & 314.635661 & 318.677126 & 309.529571 & 286.189093 & \(-\)79.09926 & \(-\)2.69\% \\ Sum & 383.085263 & 397.214904 & 396.534482 & 382.923466 & 359.2948 & \(-\)237.90463 & \(-\)6.21\% \\ \hline \hline \end{tabular}
\end{table} 
Table 7: ESV of the study area from 2000 to 2020. The temporal variation characteristics of ESV can be bifurcated into two distinct phases. The first phase spans from 2000 to 2005; this phase showed an improvement in ES functions, which may be related to regional ecological protection policies and the expansion of water bodies, where the total amount of ESV is on the rise. The second phase extends from 2005 to 2020, with the total amount of ESV showed a decreasing trend. The ESV change in water bodies over the 20-year period indicates that this trend is largely influenced by changes in water body area.