Population level risk assessments-science or fiction?

Population models are considered as one method for chemical risk assessment, especially for addressing protection goals within the ecosystem services concept (EFSA 2010). Such models have a long history in ecology and they are increasingly being used also for the risk assessment of pesticides (Barnthouse et al. 2007; Forbes et al. 2009). However, it is frequently debated to what extent population models are useful for risk assessment and if their output can be considered realistic, or if they produce rather fictitious predictions. Population models are necessarily more complex than standard methods used in pesticide risk assessment. Although the higher complexity is due to the aim to produce a population model that is as realistic as possible, it is understandable that regulators require a detailed evaluation of the realism and suitability of these models. We therefore address the question of how to evaluate whether a model is sufficiently realistic for use in pesticide risk assessment. We believe that a systematic approach may help regulators to evaluate population models.