2001) in a way that is “literal,

system-oriented, quantitative, predictive, stochastic and diagnostic” (Hansen 1996, p. 138). Indeed, simulation models have been widely applied to balance, often conflicting, economic and environmental goals (Bergez et al. 2010; Keating et al. 2003, 2010). Examples are the study of Murray-Prior et al. (2005), who used cropping systems simulation to balance trade-offs between increasing profitability while improving soil fertility, and reducing runoff and subsoil drainage in diverse rotations, including wheat and cotton, and that of Muchow and Keating (1998), who identified irrigation guidelines that maximise sucrose yield whilst minimising water losses and groundwater tapping by simulating a sugar cane farming system. Simulation models are now mainstream research tools in complex systems science (Peck 2004; Bergez et al. 2010). However, their role in assessing and quantifying sustainability beyond trade-off Captisol analyses, as discussed above, remains unclear, despite suggestion or claim of the contrary (e.g. Hansen 1996; Kropff et al. 2001). Reasons for this may be conceptual, logical, methodological or practical. Grammatically, the word ‘sustainability’ is an abstract, uncountable H 89 noun. Generic

quantifiers such as ‘some’, ‘more’ or ‘not much’ can be used to describe sustainability, but not numbers. Thus, there is incongruity between word properties and the quest for quantification. This adds to the ambiguous nature of sustainability (Cox et al. 1997), which is a hindrance to the development and adoption of a clear assessment framework, although sustainability has long been a popular notion in general terms (e.g. Kane 1999). In the following, we review some of the core issues—many arise from the relations between science Rebamipide and values that are frequently contested and ill-defined (Carrier 2008; Allenby and Sarewitz 2011; Meyer 2011; Benessia et al. 2012). Notions of agricultural sustainability are broadly centred on “the capacity of agricultural systems to maintain commodity production through time without compromising their structure and function” (e.g. Hansen 1996; Ruttan 1999; Bell

and Morse 2000). Most people would have an intuitive understanding of this and agree that agricultural sustainability is something desirable. However, broad agreement on such a public value (Meyer 2011) does not preclude conflict over definitions of sustainability, and how its presence or absence can be assessed. Theoretical concepts of agricultural sustainability have been seen as either goal-describing or system-describing (Thompson 1992). The goal-describing concept specifies a priori how the CRM1 inhibitor system ought to be, and entails normative judgements about agricultural practices and their sustainability (Cox et al. 1997; von Wirén-Lehr 2001 refers to it as means-oriented). It has been criticised as being logically flawed (Thompson 1992; Hansen 1996).