Impact of progressive urbanization and changing cropping systems on soil erosion and net primary production

• Cropping system data, RUSLE, CASA models were used to analyze the relationships among soil erosion, cropping system and NPP changes.
• By analysis, we found out that urbanization caused the total area of cropping system to decrease.
• Urbanization also caused the area of cropping systems on land that suffers higher soil erosion rate to decrease.
• Although changes of crop species, management level and climate change had caused the mean annual unit NPP to increase by 10%, decreased area of cropping system still caused total NPP to slightly decrease during 2000–2010.

As soil erosion has become a serious threat to agriculture in China, the “Grain-for-Green” project was initiated in western and central China with the goal of reducing soil erosion and improving vegetation conditions. Eastern China was not included in this project, although soil erosion is a serious problem in areas with rapid urban expansion. This study analysed the effects of urbanization on cropping system changes, soil erosion, and farmland net primary production (NPP) in Shandong Peninsula using the Revised Universal Soil Loss Equation (RUSLE) model and Carnegie Ames Stanford Approach (CASA). The results show that parts of the mountainous regions in eastern Shandong Peninsula experience severe/heavy soil erosion. The percentage of cropland experiencing high, very high, and severe soil erosion decreased by 46.1%, 60.3%, and 33.3%, respectively, from 2000 to 2010. Although the mean annual unit NPP increased by 10.8% because of changes in climate, species, and management, the total NPP of cropland still dropped slightly on the Shandong Peninsula due to urbanization, and the area of single-cropping systems on lands that suffer higher soil erosion rates decreased. However, this declining area in lands with higher soil erosion classes will help to reduce the soil erosion rate on the Shandong Peninsula, which indicates that implementing the “Grain-for-Green” project in this area is not necessary in the foreseeable future.