Pattern of cropland reclamation and abandoned land in four major black soil regions of the world and its impact on net primary productivity of vegetation in 1992—2022

Although black soil regions account for less than 7% of the global land surface, their high soil fertility and agricultural productivity make them vital for ensuring global food security. However, climate change and intensive agricultural activities have posed increasing threats of land degradation in these regions. It is crucial for understanding the mechanisms of black soil degradation and formulating sustainable development strategies to accurately characterize the spatiotemporal dynamics of cropland reclamation and abandonment, and their effects on net primary productivity (NPP). This study, based on CCI-LC global land cover data from 1992 to 2022, focuses on 4 representative black soil regions—Northeast China, the United States, Ukraine, and Argentina—to analyze the patterns of cropland change and their impact on NPP. The results show that: 1) Since 1992, the total cropland area in the 4 regions has generally increased, with an average annual growth rate of 41 000 hm2. The northeast China region has experienced continuous cropland expansion, while other regions have shown slower or even declining trends; 2) Forests, grasslands, and unused lands were the primary sources of cropland expansion, accounting for 98.1% of total reclaimed area. In contrast, cropland abandonment mainly occurred through reforestation and conversion to construction land, comprising 30.9% and 48.0% of the total abandoned area, respectively. Urban expansion was the major driver of cropland loss in China and Ukraine, while cropland conversion in the United States and Argentina exhibited more diversified trajectories; 3) From 2001 to 2022, except for Ukraine, stable croplands in the other black soil regions showed a significant increase in NPP, indicating enhanced agricultural productivity. However, NPP gains from cropland expansion were lower than those from cropland abandonment, suggesting that reclamation may reduce the carbon sequestration capacity of black soil ecosystems. This study highlights the extensive cropland expansion in northeast China’s black soil region in recent decades. Future research should focus on land-use intensity, cropland quality, and cropping structure, with deeper cross-regional comparisons to support the conservation and sustainable use of black soil resources in northeast China.