Exploring land-based ecosystem carbon sources and sinks

Our understanding of regional net carbon flux from land-based ecosystems and land-use changes has been evolving and improving as more data and advanced models become available. However, the size and attribution of carbon sources and sinks related to existing and potential land-use and land-use change (LUC) activities are still often debated, especially in the context of climate change mitigation and carbon neutrality. In this presentation, we aim to convey several key messages derived from our recent findings based on updated data and newly developed models (mechanistic and machine learning-based).   Using a new bookkeeping model (i.e., LUCE), we demonstrate that LUC has contributed to global net CO2 emissions, with forest-related activities (e.g., deforestation, reforestation) dominating changes in carbon fluxes. LUC could shift from a net carbon source to a net carbon sink in some regions with extensive gains in forest area particularly due to reforestation and afforestation. However, upon further examination of future land-use scenarios, we find that the large potential of carbon sequestration estimated from newly grown forests should be scrutinized from both ecological and socioeconomic perspectives. The role of the land sector in the global carbon budget could change over time and space, but an urgently needed positive change (from a carbon source to a sink) relies heavily on what we can and decide to do next.