Identify the spatial-temporal pattern of the increased Cultivated land and its vulnerability in Northeast China from 2000 to 2020

Ensuring compliance with China's “1.8 billion mu”(120 million hectares) cultivated land preservation policy is a fundamental goal of land policy. Northeast China has experienced significant cultivated land expan-sion due to rigorous compensation policies over the past two decades, re-sulting in sustainable increases in grain output. This research employs re-mote sensing data to examine the spatial-temporal pattern and vulnerability of newly increased cultivated land expansion in Northeast China and its potential impact on food security. Results indicate a 3.08% increase in newly increased cultivated land from 2000 to 2020, with the majority located in the Sanjiang Plain's humid area and Inner Mongolia's arid and semiarid regions. with 58.54% of it being at grade 6-10, and the reduced cultivated land all at grade 1. Additionally, 62.84% of the newly increased cultivated land was in ecologically fragile areas, while the rest were in mildly and severely vulnerable areas. Temperature insta-bility was negatively correlated with cultivated land expansion, while grain production was negatively correlated with cultivated land vulnerability. The increase in grain production at the expense of cultivated land ecology is a potential threat to national food security. The vulnerability of cultivated land is negatively and significantly related to grain yield, suggesting an adverse impact on national food security. The poor quality of newly increased cultivated land in Northeast China, characterized by ecological fragility, may lead to short-term gains in grain yield but not guarantee long-term stability. This study found a significant negative correlation between grain yield and cultivated land ecological vulnerability in Northeast China. Thus, protection measures should focus on increasing high-quality and ecologically sound cultivated land to ensure long-term grain production stability. Priority should be given to high-quality and ecologically sound cultivated land for inclusion in high-standard cultivated land construction zones to enhance protection efforts.