*4.3. Ductile Control Strategy Based on WLFC Nexus*

In this paper, the K-Medians clustering function of GeoDa was applied to cluster the values of the coupling coordination degree of "water-land-food-carbon" of China's 31 provinces, municipalities and autonomous regions in 2020, to set the criteria of internal coordination development of cultivated land-use. Combined with the level of GTCL (Figures 3–5 and Figure 9), they were divided into five levels, I to V, namely: benefit leading area, quality improvement area, connotation tapping potential area, ductile development area and ecological reserve area (Table 4).


**Table 4.** Regulation type division.

The benefit leading area (I) includes four regions, namely, Heilongjiang, Jilin, Liaoning and Inner Mongolia, whose cultivated land-use transition development and "water, land, food and carbon" coupling coordination were at a high level, especially in Heilongjiang, where the cultivated land-use transition index was as high as 0.79 in 2020, and the four subsystems were in good coordination (Figures 3, 9 and 10). Therefore, this type needs to give full play to the advantages of resource endowment and guide the cultivated land-use toward the efficient enhancement of ecological, production and living benefits, and promote farmers' income, efficient use of soil and water resources, conservation of agricultural biodiversity, and the maintenance and enhancement of soil fertility. Quality improvement area (II) includes Hebei, Shandong, Henan, Anhui, Jiangsu, Zhejiang, Jiangxi, Hubei and Hunan. The GTCL of these types of provinces was at a medium level, and the four subsystems were in low and moderate coordination (Figures 3, 9 and 10). This type of region was mostly located in the groundwater leakage area of the Huang-huai-hai Plain, and the

degradation and pollution of cultivated land due to agricultural production had obvious conflicts with ecological environmental protection and food safety guarantee. Therefore, it is urgent to introduce high-yielding and drought-tolerant food crops, promote the synergistic intensification of labor, capital, and technology to improve grain yield, and ensure food selfsufficiency based on agricultural science and technology. Connotation tapping potential area (III) includes Shanxi, Shaanxi, Beijing, Tianjin, Shanghai and Chongqing. This type of "water, land, food and carbon" coupling coordination was relatively low (Figures 9 and 10), basically in a state of reluctant coordination and low coordination, especially in Beijing, Tianjin and Shanghai, which had more carbon emissions from cultivated land-use but small grain yield. Therefore, special attention should be paid to the reduction of pesticide and chemical fertilizer use, and the implementation of carbon emission reduction and environmental pollution control. Ductile development area (IV) includes Guizhou, Sichuan, Yunnan, Guangdong, Guangxi, Fujian, and Hainan. The green development level of cultivated land-use in this type of region involved was low (Figure 4), with an average level of only 0.2, and the degree of coupling coordination of the four subsystems was also relatively low (Figures 9 and 10). Therefore, it's necessary to explore the development space of intensive use and grain yield potential in the region, and improve the ability of stable growth, efficient use, resistance to disturbance and resource support of cultivated land. In addition, farmers should be better motivated to expand grain sowing area and develop special agriculture and thus increase farmers' income. Ecological reserve area (V) includes Tibet, Xinjiang, Qinghai, Gansu and Ningxia. This type should improve the planting structure, cultivate as appropriate, pay attention to the protection of ecological functions such as water purification, CO2 regulation, hydrological regulation, biodiversity protection, farming landscape, etc. to ensure food security and ecological safety.
