The footprint of pesticide stress in communities--species traits reveal community effects of toxicants.

The predictive power of the current risk-assessment framework for pesticides remains uncertain. This is because any extrapolation towards landscape-level effects encounters considerable uncertainties: (i) when proceeding from the level of individual single-species tests to populations and communities, biological interactions are not considered; (ii) from mesocosms to field communities, environmental factors and stressors that determine the effects of pesticides in the field are not considered; and (iii) most monitoring investigations are restricted spatially and do not consider recolonisation, and lack an adequate means of distinguishing confounding factors from natural variation. We advocate using species traits as community descriptors, to determine quantitative links between pesticide toxicity and community alterations. Recently, a trait-based indicator system was developed to identify SPEcies At Risk (SPEAR) of being affected by pesticides, with reference to life-history and physiological traits. This SPEAR system has now been successfully employed to link pesticide exposure and effects in Finland, France and Germany. The effect of pesticides on the structure of communities described with SPEAR was independent of the biogeographical region. We then extrapolated and visualised the anticipated risk for aquatic communities in small agricultural streams within Europe in a risk map. With this information we identified a potential risk from pesticide runoff in a high proportion of streams. By focusing on the ecological effect of selected environmental factors, trait-based approaches offer an increased realism for risk assessment of toxicants on the ecosystem level.