Environmental impact of genetically modified crops.

Chapter 15 (Page no: 327)

European commercial genetically modified plantings and field trials.

Genetically modified (GM) maize crops expressing the Cry1Ab toxin from Bacillus thuringiensis (Bt maize) have been cultivated in Spain on a commercial scale since 1998, reaching an area of about 75,000 ha (around 21% of total maize-growing area) in 2007. A post-market environmental monitoring plan for the Bt maize varieties derived from Event Bt176 was carried out during the period 1998-2005, and a second ongoing monitoring plan for Bt maize varieties derived from Event MON810 was initiated in 2003. Both of these consider case-specific monitoring for the evolution of resistance in target insects, as well as for the potential effects on non-target arthropods. Monitoring for field resistance in target insects, Sesamia nonagrioides and Ostrinia nubilalis, is being assessed by changes in susceptibility from baseline levels. To date, no changes in their susceptibility to the Cry1Ab toxin have been found, which is consistent with the fact that there have been no control failures reported in transgenic Bt maize fields. Field trials to determine potential effects of Bt maize on non-target arthropods have focused on three functional groups: herbivores, predators and parasitoids. No detrimental effects have been observed on any of the main predatory groups that are common in maize fields. Nevertheless, field trials in the same areas for longer periods are necessary to discard long-term potential cumulative effects.

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