Quantifying the efficiency of soil conservation and optimized strategies: A case-study in a hotspot of afforestation in the Loess Plateau

Although it is generally believed the Grain for Green programme (GFG) implemented in China has attenuated soil erosion, the extent to which it is effective still needs verification. Taking Yan'an in the Loess Plateau as the study area, we analysed both total effect and efficiency differences during GFG implementation. Results showed that, while soil erosion on average decreased from 4,884.49 to 4,087.57 t km(-2)yr(-1), counties with higher GFG implementation intensity achieved a lower soil conservation effect. For example, Wuqi ranks third in the GFG implementation intensity among all counties in Yan'an, but its actual soil erosion reduction is the lowest, only 54.1% of Yan'an's average level. To analyse the reason for the efficiency difference, the concept of soil conservation potential was proposed. It is concluded that the soil conservation effect is controlled by the soil conservation potential. Ideally, regions with high soil conservation potential should get priority in the GFG application, yet there is a significant spatial mismatch between the GFG implementation intensity and the soil conservation potential because the correlation coefficient is only -0.05, which weakened the soil control effect. A dynamic implementation mechanism was put forward for the formulation and optimization of ecological programmes and projects in future: first, using the soil conservation potential to determine the implementation intensity in each region; second, adjusting the intensity to the changes of the soil conservation potential in the following implementation; third, repeating above steps to ensure high efficiency of soil erosion control, and achieving the sustainability and effectiveness of the ecological projects.