Multilevel influence mechanism of the sustainability of the Grain for Green Project in the Beijing-Tianjin Sandstorm Source Control Project.

The Grain for Green Project (GGP) has improved ecosystems and livelihoods but faces the risk of land reclamation after subsidies end. Understanding farmers' land use decisions is therefore crucial. Using 2360 questionnaires from 10-year monitoring, this study applies a "land-household-village" multilevel framework to reveal the mechanism by which farmers' resource endowments and policy incentives influence farmers' decisions to continue managing fallowed land. Results show that 33.81% of the fallowed land is at risk of abandonment. Contrary to the conventional belief that subsidies dominate, land-level factors are the primary drivers (49.9%), with high productivity being central to continued management, highlighting the importance of land quality in household resource endowments, far exceeding simple monetary incentives. Furthermore, cross-level interactions emerge: weak village governance and excessive reclamation undermine farmers' protective actions toward returned farmland, reducing their willingness to sustain management-an effect hidden in single-level analyses. These findings reveal that sustainability outcomes are shaped by stratified drivers and interactions across levels, suggesting that one-size-fits-all policies are insufficient. To strengthen GGP sustainability, strategies should focus on improving fallow land productivity, promoting non-farm employment, and enhancing village-level supervision to curb abusive practices, thereby supporting long-term land retirement in the Beijing-Tianjin Sandstorm Source Control Area.