Second generation biofuels, the production of ethanol from lignocellulosic feedstocks, are purported to have great promise for ensuring energy security and slowing the accumulation of greenhouse gases, mostly carbon dioxide, in the atmosphere. In this symposium we will explore the emerging understanding of how the wide scale deployment of biofuel feedstocks may affect local and global greenhouse gas budgets, biogeochemical cycles, and biodiversity. We seek to elucidate the economic and regulatory dimensions of biofuel production, and then to explore the contributions of ecological research to the wider debate on the merits of biofuel cultivation. We begin by exploring the greenhouse balance of biofuel crop cultivation and associated land use change. Specifically, we address biogeochemical changes associated with biofuel crop cultivation and their role in the life cycle analyses used to calculate the full GHG effects of biofuel production. In addition, we consider how biogeochemical forcings associated with biofuel crops may impact climate. We then discuss how landscapes may change as a result of biofuel cultivation, focusing both on opportunities to optimize landscapes through potentially beneficial biofuel cropping systems as well as on potential dangers to biodiversity. We end with a discussion of how ecologists can best contribute to the wider discussion on biofuels.