The Species at Risk pesticides index (SPEARpesticides) is a trait-based approach to evaluating responses of aquatic macroinvertebrate communities to pesticides. It was developed in Europe and we have now adapted and applied it to multiple regions of North and South America. In California, we developed and validated a model using the SPEARpesticides index in conjunction with simulated pesticide concentrations from a watershed-based model (Soil and Water Assessment Tool). We then used this model to predict changes in pesticide effects under future climate change scenarios. In South America, we measured concentrations of pesticides in streams and evaluated the relationships between pesticide levels, stream buffer widths, and changes in benthic invertebrate communities.
Results/Conclusions
In intensive agricultural regions in Argentina and California where there are almost no riparian buffers, we found a clear relationship between pesticide levels and changes to macroinvertebrate communities (measured by correlation between pesticide levels and SPEARpesticides values, with R2 of 0.35 to 0.53). In intensive agricultural regions in Paraguay and Brazil where there are large riparian buffers, the SPEARpesticides index did not indicate any clear effect of pesticides on macroinvertebrate communities. We predicted that without changes to management practices, there would be increases in pesticide application and in effects to macroinvertebrate communities in California. This increase in effects would be most pronounced in regions with lower agricultural intensity and lower temperatures, and would occur assuming no increase in agricultural activity. We are currently using the SPEAR and SWAT tools to model various scenarios with mitigation by implementation of different management practices, focusing on increasing riparian buffers and changes in types of pesticides used.