Trade-offs between economic benefits and environmental impacts in non-grain expansion: a case study in the eastern plain of China

China has experienced a boom expansion of non-grain production in recent years. While the non-grain production can increase the economic benefits of farmers, its expansion has significant impacts on the ecological environment and agricultural sustainability. This study attempted to assess the trade-offs between the economic benefits and environmental costs of non-grain production and to provide reference for future land use management. Focusing on the non-grain expansion in Tongxiang City, eastern China, empirical models and field surveys were used to evaluate its environmental impacts and monetary analysis was used to assess the trade-offs between the economic benefits and environmental costs. The results showed that the area of non-grain production increased by 2464.74 ha from 2005 to 2020, and pond fish farming accounted for the largest proportion. The economic benefits and environmental costs of non-grain production increased continuously during 2005–2020, and the net economic–environmental benefits gradually expanded after 2010. Trade-off analysis indicates that the economic benefits of duck rearing did not compensate for the environmental costs, while the other non-grain productions did. Nevertheless, the potential impact of non-grain conversion on the local environment is still underestimated. Some suggestions are proposed to achieve a win–win situation between cultivated land utilization and ecological protection.