Diminishing returns and rising ecological costs of cropland reclamation in China’s four northern provinces

Cropland reclamation has helped meet growing food demand but has also generated substantial ecological costs. While previous studies have primarily examined this issue at national or broader scales, local heterogeneity remains insufficiently understood. Here, we focus on four northern provinces of China, which represent a key frontier of cropland reclamation. Between 2000 and 2020, newly reclaimed cropland accounted for 17% of the cropland area in 2000, and contributed to grain yield growth during the initial decade. However, after 2010, cropland reclamation played a diminishing role in supporting grain production. Meanwhile, biodiversity intactness continued to decline. These findings reveal an unsustainable trade-off, in which marginal gains in production diminished while ecological costs accumulated over time. Closing yield gaps in low-productivity croplands could increase annual grain output by up to 5.24 million tonnes and reduce the need for further cropland reclamation. Thus, prioritizing yield gains over new reclamation offers a pathway to balancing food security and biodiversity conservation.