In spite of its decreasing share of global economic output, agriculture is still responsible for a large part of overall physical output, both to the rest of the economy and to the environment. For example, it has been estimated that agriculture and land use are responsible globally for around 24% of the greenhouse gas emissions fuelling climate change. A prerequisite to improving the sustainability of agriculture are reliable methods to identify and quantify types of environmental impact. These can then be used to identify priorities, set targets for improvement and monitor progress. This book provides a review of current research on the use of life cycle assessment (LCA) and other modelling techniques to measure and model the environmental impact and improve the sustainability of agriculture. The book is divided in three parts. Chapters in Part 1 review key issues in using LCA and modelling applied to farming systems. Part 2 provides more detail on the modelling of three particular impacts, namely freshwater, pesticides and social impacts. Part 3 looks in more detail on options for reducing the environmental impact and improving the performance of both crop and livestock farming.