This project is evaluating the fundamental interactions between human and terrestrial systems through agriculture and land use, driven by forces that are global in nature and moderated by climate and atmospheric composition. It aims to address the global consequences of human interactions on earth systems, and the consequent feedbacks on the economy. The approach is to model these interactions with complex but separate models of human activity, of the atmosphere and ocean, of the terrestrial systems, and sector-by-sector models of economic and human effects, and to evaluate the costs and potential feedbacks of changes in atmospheric composition and climate. Specific aims include: (1) the effects of more realistic and complex interactions of air pollution or climate policy, separately or in combination, on vegetation including crops; (2) the resultant impacts on the economy and adaptive response to these changes including international market repercussions; and (3) the ultimate feedback on the cost of the policies, economic growth, and/or the emissions of the pollutants themselves. The effects and changes, and their interactions, are complex. For example, some effects, such as N deposition and CO2 fertilization, are beneficial to vegetation while others such as tropospheric ozone are mostly damaging, and still others, such as climate change, can be either beneficial or detrimental. The project is supported by an award resulting from the NSF special competition in Biocomplexity in the Environment focusing on the Dynamics of Coupled Natural and Human Systems.