Impacts of Land-Use–Environment Interactions on Anthropogenic and Natural Sources and Sinks of CO2

Global land use has evolved from an activity focused on providing food and fiber, with climatic impacts occurring mostly as side effects, to additionally becoming a central player in climate change mitigation. While global land-use change (LUC) historically contributed one-third to anthropogenic CO₂ emissions, the land ecosystem as a whole has acted as a CO₂ sink in recent decades, as environmental changes often created more favorable growth conditions. When LUC and environmental changes are considered together, however, carbon flux attribution becomes non-unique: their interaction generates non-additive fluxes that cannot be clearly separated into direct anthropogenic (LUC) and indirect anthropogenic and natural (environmental) drivers. Here we synthesize the progress in quantifying global land-use impacts on the Earth system and highlight the critical role of land-use–environment interactions, such as replaced and (re-)established sinks and sources. We show that these interaction terms are essential for understanding past land carbon dynamics and that they will increasingly shape future land-atmosphere CO₂ exchange, as land-based mitigation of climate change is expected to expand and climate impacts will intensify. Addressing these challenges will require coordinated advances in model development, disturbance representation, overshoot scenario analysis, and observation-based attribution frameworks to robustly quantify future land-use–environment interactions and their role in the global carbon cycle.