Maximum Carbon Sequestration from Cropland Abandonment in China over the Past Thirty Years

Cropland abandonment is a widespread phenomenon globally, including in China. However, the role of carbon sequestration on abandoned cropland in climate change mitigation remains uncertain, largely due to the dynamic interplay between abandonment and recultivation as well as inconsistencies in definitions across studies. The duration of continuous abandonment is a key determinant of carbon sequestration magnitude. In this study, the maximum continuous abandonment duration for each pixel across China was mapped using annual land-use maps from 1990 to 2025. The maximum carbon sequestration potential—expressed as cumulative Net Ecosystem Productivity (NEP)—was then estimated by integrating these duration data with corresponding annual NEP. Results show that the average maximum abandoned duration is 14.62 years, with the 6–10 years category accounting for the largest proportion of abandoned pixels (24.50%). In contrast, longer duration categories (26–30 years and >30 years) represent only 10.44% and 3.72%, respectively, indicating that most abandoned cropland is recultivated before substantial net carbon accumulation (reflected in positive NEP) can occur. Sensitivity analysis suggests that the choice of threshold duration has only a marginal influence on estimates of abandoned area and duration. The total maximum net carbon sequestration from cropland abandonment over the study period amounts to 79 Tg C, which is lower than the emission reduction potential achievable through appropriate agricultural management measures. A comparative analysis of emissions and sequestration indicates that relying solely on vegetation recovery for CO2 removal is insufficient to support carbon neutrality objectives within the cropland system. These findings underscore the need to prioritize emission-reduction strategies in agricultural management over passive reliance on abandonment-driven carbon sinks.