"Besides the widely acknowledged drawbacks of GMCs: a) the spread of
transgenes to related weeds or conspecifics via crop-weed hybridization and, b)the rapid
evolution of resistance of insect pests such as Lepidoptera to Bt, the workshop was
concerned about the overall ecological implications of other more subtle effects that
research is now starting to unravel: accumulation of the insecticidal Bt toxin, which remains active in the soil after the crop is ploughed under and binds tightly to clays and humic acids; disruption of natural control of insect pests through intertrophic-level effects of the Bt toxin on predators; unanticipated effects on non-target herbivorous insects (i.e. monarch butterflies) through deposition of transgenic pollen on foliage of surrounding wild vegetation; vector-mediated horizontal gene transfer and recombination to create new pathogenic organisms, and reduction of the fitness of non-target organisms through the acquisition of transgenic traits via hybridization.
By examining specific studies that describe such effects, the group was able to assess the
scale, magnitude and ecological significance of such findings."