## 3 Results
### Evolution Characteristics of the ESV in Different Landform Types  
#### 3.2.1 Temporal and Spatial Variation in the ESV in Different Landform Types  
Formula (1) was used to calculate the ESV of different karst areas (Table 4). At the same time, due to the different areas of each landform type, the ESV per unit area was used for comparative analysis (Figure 5). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Landform Type** & **1985** & **1990** & **1995** & **2000** & **2005** & **2010** & **2015** & **2020** \\ \hline
**Pure-karst** & 16,813.80 & 16,843.23 & 16,788.89 & 16,718.96 & 16,433.59 & 16,348.35 & 16,328.07 & 16,691.97 \\
**Semi-karst** & 7457.10 & 7435.42 & 7430.28 & 7473.36 & 7404.59 & 7397.36 & 7527.33 & 7824.02 \\
**Non-karst** & 18,477.01 & 18,543.43 & 18,644.94 & 18,642.87 & 18,257.30 & 18,459.58 & 18,417.84 & 18,617.27 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Total ESV of different karst landform types, 1985–2020 (unit: USD million). Figure 5: ESV per unit area in different karst landform types from 1985 to 2020. As can be seen from Table 4, the total ESV in each period in the past 35 years was as follows: non-karst areas > pure-karst areas > semi-karst areas. The total ESV in the pure-karst areas was USD 16.814 billion in 1985 and USD 16.692 billion in 2020, a decline of USD 122 million over the past 35 years, with an average annual decline of USD 4 million, or a reduction rate of 0.72%. From 2000 to 2005, the ESV declined the fastest, with an average annual decrease of USD 57 million. From 2015 to 2020, the ESV increased the fastest with an average annual increase of USD 73 million. The total ESV increased to varying degrees in the semi-karst and non-karst areas. The total ESV increased by USD 367 million in the semi-karst area, with an average annual increase of more than USD 0.01 billion. From 2000 to 2005, the ESV declined the fastest, with an average annual decrease of USD 14 million. From 2015 to 2020, the ESV increased the fastest at USD 59 million/year. The total ESV in the non-karst area increased by USD 140 million, and an average annual increase of USD 4 million, with a growth rate accounting for approximately 0.76%, comparable to the rate of decrease in the pure-karst area. The fastest rate of decrease and the fastest rate of increase in the non-karst areas were in the same time period as the pure-karst and semi-karst areas. From 2000 to 2005, the ESV decreased at an average annual rate of USD 77 million, while from 2015 to 2020, the ESV increased at an average annual rate of USD 40 million. From the ESV per unit area in different karst-landform-type areas (Figure 5), the results were as follows: non-karst areas > pure-karst areas > semi-karst areas. The ESV per unit area in all three landform areas showed an increasing trend, with a downward trend from 2000 to 2005. The reason for this is that, after 2000, with the implementation of the Western Development Strategy and the increasing level of urbanization and industrialization in Guizhou Province as well as the concentration of the rural population in the cities, the urbanization rate increased by nearly 3 percentage points, and the area of construction land expanded, resulting in a decrease in the area of ecological land, which negatively affected the value of regional ecosystem services [55]. With the introduction of the \"Opinions of Guizhou Provincial People's Government on Improving the Grain for Green Policy ([PERSON] [2007] No. 35)\" in 2007 and the \"Work Plan of Combining Forest and Grass for the New Round of Grain for Green Project in Guizhou Province\" in 2016, and the enhancement of human awareness of ecological environmental protection, the forest coverage rate of Guizhou Province reached 61.51% in 2020, and the ESV per unit area increased year by year. Among the ESV of land-use types in each karst-landform-type area, the contribution of the cropland, forest, barren land, and water ESV increased slightly in the pure-karst area.