4.2 Spatial distribution relationship between the SCE and the GFG intensity
Figure 4a provides the spatial distribution of GFG intensity (the ratio between the area of cultivated land converted to forest or grassland and the area of original cultivated land in a region) in Yan’an, which shows significant spatial agglomeration. The high-intensity areas of GFG are concentrated in Wuqi, Baota, Zichang, and Luochuan. The low-intensity areas are mainly distributed in Ansai, Huanglong, Yanchang, and Ganquan. It can be seen that this agglomeration is controlled by the county boundaries. This is because, in China, the formulation and implementation of related measures of the GFG are based on counties, so there can be significant differences in the intensity of GFG among counties. Figure 4b shows the SCE produced by GFG in Yan’an. It can be found that its spatial distribution also has an obvious agglomeration effect. The areas with obvious SCE are mainly distributed in the east, south, and Ansai in the north. While counties such as Wuqi, Zhidan, and Baota have achieved certain results in soil conservation, they are not as obvious as in other regions.
[Figure 4 near here]
Although the above two indicators have their specific spatial distribution law, the correlation between them is not significant, and the correlation coefficient is only −0.12. By comparing Figure 4a and 4b, it can be found that Wuqi, Baota, Zichang and other places with higher GFG intensity have lower SCE. Yanchuan, Yanchang, and Yichuan, where the SCE are obvious, have less GFG intensity. This situation reflects the mismatch between the GFG intensity and the SCE in spatial distribution. That is, the SCE is not necessarily better in areas with relatively high GFG investment. Considering that the main purpose of GFG in this region is soil conservation, it can be considered that the current GFG does not achieve optimal input allocation.
As mentioned earlier, the optimal allocation of GFG investment should be concentrated in regions with greater SCP. Therefore, we compared the SCP before GFG (Figure 4c) with the GFG intensity (Figure 4a). It was found that the matching degree of SCP and GFG at the spatial level was low, and the correlation coefficient was only −0.05, which was obviously inconsistent with the theoretical analysis. Considering that the GFG is mostly implemented at the county level, the SCP before GFG and the GFG intensity of all counties in Yan’an were ranked and compared. As shown in Table 3, the ranking difference of most counties is large, which further validates their inconsistencies. Taking Wuqi as an example, the county has the least SCP before GFG. While its GFG intensity ranks the 3rd, indicating that the GFG intensity in Wuqi has far exceeded the reasonable range of soil conservation. On the contrary, Yanchuan, Yanchang, and Yichuan in eastern Yan’an, which have the greatest SCP before the GFG and should have the highest GFG intensity theoretically. However, the GFG intensity rankings are far from the SCP, which indicates that the implementation of GFG in these areas needs to be improved. These results indicate that the previous GFG investment did not take into account the SCP, not only failed to achieve the optimal SCE, but also caused a waste of resources. If the GFG investment can be formulated and adjusted according to the SCP in each region, the implementation efficiency of GFG can be greatly improved, so as to achieve better SCE.
[Table 3 near here]
To better illustrate the above point, we calculated the ratio of the GFG area and the soil erosion reduction (RGS) from 2000 to 2015. Comparing the GFG areas in several counties under the premise of achieving the same SCE (Table 4). Obviously, the RGS of Wuqi (1.836) is much higher than that of Yanchang (0.105), Yichuan (0.196), and Yanchuan (0.307). That is, under the premise of achieving the same SCE, the GFG investment in Wuqi needs to be higher. The result indicates that if the focus of GFG investment can be placed on counties with great SCP, the investment cost of GFG will be significantly reduced, thereby saving capital and resources.
[Table 4 near here]