摘要：At present, the return of farmland to forests is the key ecological conservation policy in use to control soil erosion and restore the eco-environment of the Loess Plateau, China. In order to explore policy-driven ecological defarming scenarios, Ansai County is taken as a case study. The land use map in 2000 and the topographic and slope map (taking the defarmed slopes with 15°, 20°, and 25° as the defarming thresholds) were used, supported by spatial analysis techniques in geographic information systems (GIS). This paper simulates and analyzes the scale and spatial difference of ecological defarming of Ansai County, the subsidy demand for defarming, and the influences of defarming on agricultural development. The results show: (1) The area of defarmed land with slopes greater than 25° in Ansai amounts to 3451.05 ha, which accounts for 2.84% of total area with slopes over 25°, and the defarming index will be 3.14%. The total subsidy demand for defarming land will be 6884.84 × 10 4 yuan (RMB) or US$ 1008.03 × 10 4 . The loss of agricultural food products that results from defarming will be 955.17 t in the average year, or 1.66% of total average annual production. (2) The area of defarmed land with slopes over 20° in Ansai will increase to 36,281.61 ha, which accounts for 19.74% of total area with slopes over 20°, and the defarming index will be 32.96%. The total subsidy demand for defarming land will be 72,381.81 × 10 4 yuan or US$ 10,597.63 × 10 4 . The loss of agricultural food products due to defarming will be 10,041.9 t in the average year, or 17.50% of total average annual production. (3) The area of defarmed land with slopes over 15° in Ansai increases to 101,807.99 ha, which accounts for 37.23% of total area with slopes over 15°, and the defarming index will be 92.49%. The total subsidy demand for defarming land will be 203,106.94 × 10 4 yuan or US$ 29,737.47 × 10 4 . The loss of agricultural food products owing to defarming will be 28,178.06 t in the average year, or 49.10% of total average annual production.
