Implementing isolation perimeters around genetically modified maize fields

Due to the growing cultivation area of genetically modified ( GM) maize and the rising number of GM maize varieties commercially available to European farmers, the co- existence between GM and non- GM maize is becoming a burning issue in some European regions. Hence, Member States are imposing or discussing specific co- existence measures to keep the adventitious presence of GM material in non-GM produces below the established labelling threshold. As maize is a cross- pollinated crop that uses wind for the dispersal of its pollen, on- farm co- existence measures may rely on the spatial isolation of GM and non- GM maize fields. In this study, we developed an approach that combines geographic information system ( GIS) datasets with Monte Carlo simulations to assess the feasibility of implementing isolation perimeters around GM maize fields, since its practical implementation is rarely addressed in the co- existence debate. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation perimeters in two agricultural areas in Flanders ( Belgium). The GIS analyses emphasised the small size of maize fields and their scattered distribution throughout the cropped area. The feasibility of implementing isolation perimeters was largely affected by the ( GM) maize share, the spatial distribution of GM maize, and the width of isolation perimeters. The higher the ( GM) maize share and the wider the isolation perimeter, the higher the proportions of farmers with non- GM maize fields occurring within the implemented isolation perimeter. Compared with randomly distributed GM maize fields, the clustering of GM maize fields on a larger scale and at the farm level increased the feasibility of implementing isolation perimeters. The approach developed proved to be a valuable tool to quantify the feasibility of implementing isolation perimeters under real agricultural conditions.