Are concerns about feral genetically modified herbicide tolerant oilseedresulting from seed import spills scientifically justified?

Abstract: One of the concerns surrounding the import (for food and feed uses or processing) ofgenetically modified herbicide tolerant oilseed rape (GMHT OSR) is that, through seed spillage,the herbicide tolerance (HT) trait will escape into agricultural or semi-natural habitats, causingenvironmental or economic problems. Whether the concerns posed by feral GMHT OSR fromseed import spills are scientifically justified is debatable. While OSR has characteristics such assecondary dormancy and small seed size that enable it to persist and be redistributed in thelandscape, the presence of ferals is not in itself an environmental or economic problem.Crucially, feral OSR has not become invasive outside cultivated and ruderal habitats, and HTtraits are not likely to result in increased invasiveness. Feral GMHT OSR has the potential tointroduce HT traits to volunteer weeds in agricultural fields, but would only be amplified if theherbicides to which HT volunteers are tolerant were used routinely in the field. This worst-casescenario is most unlikely, as seed import spills are mostly confined to port areas. Economicconcerns revolve around the potential for feral GMHT OSR to contribute to GM admixtures innon-GM crops. Since feral plants derived from cultivation (as distinct from import) occur at toolow a frequency to affect the coexistence tolerance threshold of 0.9% in the EU, it can beconcluded that feral GMHT plants resulting from seed import spills will have little relevance as apotential source of pollen or seed for GM admixture. This paper concludes that feral OSR inEurope should not be routinely managed, and certainly not in semi-natural habitats, as thebenefits of such action would not outweigh the negative effects of management.