Butterflies for post market environmental monitoring of GM maize in Spain

Abstract: The only genetically modified (GM) maize planted in Europe is Bt maize resistant to lepidopteran stemborers, cultivated on a large scale in Spain. Maize expressing herbicide tolerance and insect resistance traits singly or stacked will predictably also be cropped in the future. EC legislation demands that an environmental risk assessment (ERA) for GM crops be carried out prior to release into the environment and that they be monitored after release by the implementation of post market environmental monitoring (PMEM) to detect possible adverse effects unanticipated in the ERA. Butterflies are often used for monitoring because they are sensitive to environmental changes, they are relatively easy to see and identify in most cases they are socially valuable. For PMEM of GM maize butterflies are particularly meaningful because they belong to the same taxonomic group as the target insect in the case of maize expressing Bt toxins and they feed on weeds that could be affected by the herbicide regime of HT maize. There is little information regarding butterfly species that can be exposed to the hazard of those two types of GM traits and which could be used for PMEM in southern European countries. This study addresses this knowledge gap and, after a bibliographic search and a year of field sampling, identifies some potential indicator species.Other studies have found that the number of samples needed to detect even large changes in butterfly populations is impracticable. Thus, ways to integrate PMEM into existing monitoring schemes that cover large areas of Europe, such as the butterfly monitoring scheme (BMS), are discussed.