Regionally Unbalanced Improvement of Cultivated Land Soil Quality in China since the 1980s

Cultivated land plays an important role in ensuring food security and achieving the Sustainable Development Goals (SDGs). However, the long-term spatiotemporal changes in cultivated land soil quality (CLSQ) at national scales are poorly quantified. Here, we provide the first comprehensive assessment of the spatiotemporal variations of CLSQ in China with 1 km resolution from the 1980s to 2010s, using a machine learning approach based on over 190,000 soil samples and environmental variables from all of China. The average CLSQ grade in China has significantly improved by 8.6 % (0.46 grades) over the past three decades. However, these changes are regionally unbalanced. Spatial patterns show that the Huang-Huai-Hai Plain experienced the biggest increase in high quality cultivated land since the 1980s, while in Northern and Western China there was an increase in low quality cultivated land from the 2000s, implying that these regions are facing cultivated land degradation. The unbalanced improvement of CLSQ in China reveals the impact of human activity on cultivated land soil quality and the importance of improving cultivated land soil quality in ecologically sensitive regions to ensure food and environmental sustainability.

耕地对于保障粮食安全、实现可持续发展目标（Sustainable Development Goals, SDGs）具有关键作用。然而，当前针对国家尺度下耕地土壤质量（Cultivated Land Soil Quality, CLSQ）的长期时空变化的量化研究仍较为匮乏。本研究基于全国范围内超过19万份土壤样本与环境变量，采用机器学习方法，首次完成了1980年代至2010年代中国耕地土壤质量时空分异的全面评估，空间分辨率达1千米。过去三十年间，中国耕地土壤质量平均等级显著提升了8.6%（即0.46个等级）。但此类变化存在显著的区域不均衡性。空间格局分析显示，自1980年代以来，黄淮海平原的高质量耕地面积增幅最为显著；而华北与西北地区自2000年代起低质量耕地面积有所增加，表明这些地区正面临耕地退化问题。中国耕地土壤质量改善的不均衡性，揭示了人类活动对耕地土壤质量的影响，同时也凸显了在生态敏感区域提升耕地土壤质量以保障粮食与环境可持续性的重要意义。