Background Yulin, located in the north of Shaanxi province, is one of the most serious soil loss and fragile districts of ecology in the middle reaches of the Yellow River in China. The ecological fragile environment causes threat for the sustainable development of economical society. The Grain for Green policy was launched by the Chinese government in 1999, resulting in the ecological environment nowadays becoming better. This indicated by the obviously reduced soil erosion. However, changes of soil erosion in the future are important to the ecological environment in Yulin city, which is related to the sustainable development of Grain for Green policy.

Methods To investigate the benefit of soil and water conservation and the change trend of soil erosion under Grain for Green Project in Yulin, the Least Square Method and Neural Network Model were used to predict the vegetation cover and land use types in the future. The soil erosion series from 2000 to 2017 was calculated by the slope water erosion equation used in China. The future soil erosion modulus was simulated under the conditions of the min/max and the multi-year average rainfall erosivity.

Results 1) The annual average rainfall erosivity of the hilly and gully areas, western area and northern region ranged from 1 150 to 1 350 MJ·mm/(hm²·h), from 800 to 1 050 MJ·mm/(hm²·h) and from 1 000 to 1 150 MJ·mm/(hm²·h), respectively. Compared with from 1988 to 2000, the average rainfall erosivity of from 2001 to 2017 increased by 268.24 MJ·mm/(hm²·h). 2) The soil erosion modulus under the annual average rainfall erosivity decreased significantly from 3 559.99 t/(km²·a) in 2000 to 1 369.19 t/(km²·a)in 2017, and the amount of soil erosion decreased by 9.585×10⁶ t. 3) The vegetation coverage (C) factors decreased from 0.164 (year 2000) to 0.069 (year 2017), and the predicted future C factor was 0.053. However, the Hurst index showed that the C factor in the future will increase up to 51%. This result shows that there is a risk of vegetation degradation in the future, especially for county of Jingbian, Shenmu, Dingbian, Fugu, and Hengshan as well as Yuyang district. 4) In future, the soil erosion modulus in the most areas will be < 2 000 t/(km²·a), mainly mild and slight.

Conclusions These results suggested that the modulus of soil erosion in this area will be < 2 000 t/(km²·a) in the future. Soil erosion intensity is mainly slight and light erosion. The ecological environment will be improved further. In the next stage, the more attention should be pay to water resources carrying capacity and the ecological and soil and water conservation benefits.