## 3 Results
### ESV Analysis  
#### 3.2.1 Time Variation Analysis of the ESV  
The total ESV in Shaanxi Province increased initially and then decreased during the research period (Table 5). The total value rose from USD 3802.82 billion in 1990 to USD 3814.90 billion in 2000, rose further to USD 3836.20 billion in 2010, and then declined to USD 3806.50 billion in 2020. Before the implementation of the project, the total ESV in Shaanxi Province increased by 0.32%; the growth rate slowed after the implementation of  
Figure 3: Spatial distribution of land-use in Shaanxi Province from 1990 to 2020. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**1990**} & \multicolumn{6}{c}{**2000**} \\ \cline{2-7}  & **Farmland** & **Foresland** & **Grassland** & **Water Areas** & **Built-Up Land** & **Barren Land** \\ \hline Farmland & 7,122,855.87 & 5980.59 & 55,325.07 & 8615.43 & 42.48 & 3296.16 \\ Forestland & 11,240.01 & 4,592,455.74 & 25,334.28 & 108.36 & 2.07 & 6763.77 \\ Grassland & 5923.44 & 15,703.47 & 7,623,471.69 & 3338.91 & 7.11 & 129,499.57 \\ Water areas & 3624.03 & 156.24 & 2483.64 & 174,302.19 & 0.36 & 841.41 \\ Built-up land & 35,707.32 & 1859.94 & 852.21 & 28.35 & 276,464.70 & 298.26 \\ Barren land & 3543.75 & 231.84 & 8134.66 & 293.04 & 0.27 & 474,849.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Land-use transfer matrix of Shaanxi Province from 1990 to 2000.  
the project, with a growth rate of 0.10% throughout the study period. The main reason for this is that the built-up area increased, and the ESV provided by built-up land is negative. Grassland had the highest ESV, followed by forestland and farmland. The ESV of farmland reached its maximum level in 2000, and the ESV given after the project's implementation continued to decline. The forestland ESV grew over the analyzed period. Although the ESV provided by grassland decreased in the later period, it also exhibits an increasing trend in general. The ESVs of water areas, built-up land, and barren land all fell in varying degrees, owing mainly to the continuous reductions of water areas and barren land. Although the total area of built-up land increased, the ESV provided by built-up land is negative, so the value decreased, and the change was most apparent. Based on the changes in ESV in Shaanxi Province from 1990 to 2020 (Table 6), the proportion of each single ESV was relatively stable, in the following order: hydrological regulation > climate regulation > glimate regulation > gas regulation > biodiversity maintenance > environment purification > environment purification > aesthetic landscape > raw materials > nutrient-cycle maintenance > water supply. Before the implementation of the GGP, aside from the decreasing trends in water supply services and environmental purification services, all kinds of services exhibited increasing trends. Food production, hydrological regulation, and nutrient-cycle maintenance services showed a decreasing trend to different degrees after project implementation. After the implementation of the project, the ESV showed varying degrees and different directions. Over the whole research period, the ESV increased for raw materials, gas regulation, climate regulation, soil conservation, biodiversity maintenances, and aesthetic landscape, among which aesthetic landscape showed the greatest increase. ESV decreases were observed for food production, water supply, environmental purification, hydrological regulation, and nutrient-cycle maintenance, among which the greatest decrease was for water supply.