Environmental impact assessment for a farming region: a review of methods

The methods currently used for assessing the environmental impact of agriculture on the scale of a farming region cover a wide range of objectives, users and concepts. To illustrate this variety, this article provides an analysis of six main types of method: environmental risk mapping, life cycle analysis, environmental impact assessment, multi-agent system, linear programming and agro-environmental indicators. Eleven case studies, in which one of the six methods was applied, are used as data in this review. All methods are based on a set of environmental objectives. Some methods also take account of economic and social objectives to produce a more wide-ranging assessment of the sustainability of the agricultural system studied. Each method relies on indicators serving as criteria to evaluate whether the objectives have been attained. These indicators take account of local impacts such as noise, regional impacts such as eutrophication, or global impacts like the greenhouse effect. The characteristics required to develop a method for the environmental impact assessment of a farming region are discussed. The analysis of the interactions between farms is indispensable at this scale of analysis. Indicators based on the environmental effects of farming practices should take precedence over those based on the practices themselves, which do not provide a direct evaluation of environmental impact. Indicators which express an impact both per kg of product and per unit of land area used bring together the essential functions of agriculture, namely production and the occupation of the countryside. The assessment methods should include an analysis of the uncertainty associated with the results. Lastly, the method should be validated with respect to (i) the conception of the method and its indicators, (ii) the consistency of the values of the indicators in relation to observed values, and finally (iii) the suitability of the indicators and more generally of the assessment method for the end users.