Credibility and acceptability of mathematical models of environmental impacts of agriculture in The Netherlands

A conceptual framework of credibility and acceptability is applied to a simple and a complex model to examine their usefulness in making decisions. The complex model was found to be not credible, i.e. not technically appropriate for its task, although a great deal of effort was put into its development. The condition of a relatively complete and thus large and complex model makes this finding almost unavoidable. Despite the low credibility, the acceptability of the complex model and its results is sufficient. The acceptability of the model is, however, not a guarantee that its results determine the outcomes of the decision making process. The simple model is credible for the variables included and for the area for which it was built. Its acceptability is limited as it is only applicable to a specific area and because the link with actual ecological effects is weak.