Environmental impacts of farm scenarios according to five assessment methods

It is not known to what extent the outcome of studies assessing the environmental impacts of agricultural systems depends on the characteristics of the evaluation method used. The study reported here investigated five well-documented evaluation methods (DIALECTE, Ecological Footprint, Environmental Management for Agriculture, FarmSmart, Life Cycle Assessment) by applying them to a case study of three pig farm scenarios. These methods differ with respect to their global objective (evaluation of impact versus evaluation of adherence to good practice), the number and type of environmental issues they consider, the way they define the system to be analysed, the mode of expression of results (for the farm as a whole, per unit area or per unit product) and the type of indicators used (pressure, state or impact indicators). The pig farm scenarios compared were conventional good agricultural practice (GAP), a quality label scenario called red label (RL) and organic agriculture (OA). We used the methods to rank the three scenarios according to their environmental impacts. The relative ranking of the three scenarios varied considerably depending on characteristics of the evaluation method used and on the mode of expression of results. We recommend the use of evaluation methods that express results both per unit area and per unit product. Environmental evaluation methods should be used with great caution, users should carefully consider which method is most appropriate given their particular needs, taking into consideration the method's characteristics.