Croplands as thermodynamic agents in a high-CO2 world

David Helman 

Rising atmospheric CO2 is widely expected to influence crops through physiological pathways, yet croplands are also extensive physical interfaces that regulate land–atmosphere energy exchange. Despite covering 12–15% of Earth’s ice-free land surface, their role in surface energy balance under elevated CO2 remains poorly constrained. Most CO2 enrichment studies have not explicitly resolved the surface energy balance, and current models rely on simplified representations of canopy physical properties. As a result, potential CO2-driven changes in radiative exchange, aerodynamic coupling, and energy partitioning remain largely untested. Here I propose a thermodynamic framework for crop–atmosphere interactions that identifies these missing pathways and formulates testable hypotheses linking canopy processes to boundary-layer dynamics. Resolving these mechanisms is essential for improving projections of land–atmosphere coupling and agricultural climate risk.