The number of life cycle assessment (LCA) and LCA-based footprint studies comparing food products coming from different agricultural production systems, reflecting different production intensities, is rapidly growing providing an increasing amount of data for further analyses. This chapter examines the use of LCA to compare intensive with extensive agricultural systems. The chapter addresses the validity of LCA studies comparing intensive and extensive agricultural systems and looks at assessing validity at the inventory level (using the example of reactive nitrogen emission modeling and monitoring heavy metal emissions in different farming systems).