Forest carbon flux monitoring is vital for regional forest management and bolstering natural carbon sinks. However, accurately estimating the net carbon balance of forest cover change and its anthropogenic drivers in rapidly urbanizing areas remains a challenge. Here, we employed an online real-time monitoring technology integrating Google Earth Engine, Continuous Change Detection and Classification (CCDC) algorithm, and spatial bookkeeping (SBK) model to track forest-loss emissions and forest-gain uptakes in the Yangtze River Delta of China from 2000 to 2020. Our results revealed a net gain of 109,500 ha of forest area during this period, yet overall forest cover changes acted as a net carbon source (-2.95 TgCyr^-1). Newly established forests in the YRD exhibited limited carbon sequestration capacity, offsetting only 24% of forest-loss carbon emissions and 0.28% of energy-related carbon emissions. Urban expansion, agricultural expansion, and other forest losses contributed 37%, 10%, and 53% of total forest-loss emissions, respectively. Conversely, the Grain for Green activity contributed to 45% of forest-gain uptakes, with other forest gains making up the remaining 55%. Our findings underscore the critical importance of monitoring and avoiding deforestation and implementing comprehensive forestry ecological and greening projects to mitigate carbon emissions.

forest cover change,Google Earth Engine（GEE）,CCDC,spatial bookkeeping model,Carbon fluxes