Agri-environmental indicators to assess cropping and farming systems. A review Christian Bockstaller, Laurence Guichard, David Makowski, Anne Aveline, Philippe Girardin and Sylvain Plantureux Agron. Sustain. Dev., 28 1 (2008) 139-149 Published online: 29 February 2008 DOI: 10.1051/agro:2007052