Quantitative analysis of economic and environmental benefits for land fallowing policy in the Beijing-Tianjin-Hebei region.

The Beijing-Tianjin-Hebei region (BTH region) is a major crop-producing region of China suffering from environment deterioration. Land fallowing policy is widely used as the solution of agriculture-related environment pollution, while it is difficult to derive a quantitative basis for policy-making. An indicator system was established to quantitatively analyse economic and environmental benefits of land fallow policies in the BTH region. The system consisted of 8 indicators to describe the water, air and economic influences caused by land fallowing policy such as the amount of nutrient discharged, the emission of PM2.5-related and greenhouse gas, and the input and output of agriculture production. SWAT (Soil and Water Assessment Tool) and IAP-N (Improving Anthropogenic Practices of managing reactive Nitrogen) models were used to quantify environmental indicators. Five scenarios with different planting patterns and fallow intensities were simulated for five years with different hydrological conditions. It is found that the influence of policy on water environment is highly sensitive to hydrological conditions, while the influence on air environment and economy are more affected by different policy settings in scenarios. The marginal utilities of the fallowed area are indicator-dependent. Planting alternative crops can decrease production costs and keep crop yields, while may also cause atmospheric environmental pollution if the crops have nitrogen fixing ability. Indicators also have spatial and temporal heterogeneity under different planting patterns and fallow intensities. A policy evaluation and associated uncertainty analysis is essential for effective implementation. The analysis framework established could support decision-making in regions facing agri-environmental problems.