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Submitted to: CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/27/2009 Publication Date: 4/6/2009 Citation: Naranjo, S.E. 2009. Impacts of Bt crops on non-target organisms and insecticide use patterns. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources. 4 No 011 1-23. Interpretive Summary: As of 2007, maize and cotton that have been genetically engineered for resistance to caterpillar and beetle pests (Bt crops) were grown on ˜38 million hectares in 20 countries. A major concern of this technology has been environmental safety, specifically effects on non-target organisms. This review focuses on non-target effects and on changes in insecticide use patterns since the adoption of Bt crops. The first aspect is reviewed through a meta-analysis of the existing scientific literature. The method allows the results of multiple independent studies to be combined so that general patterns can be elucidated. This analysis revealed that non-target impacts vary in relation to taxonomy, ecological or anthropomorphic category, the route of exposure to Bt toxins, and the non-Bt control against which effects are gauged. Hazards identified in the laboratory may not always manifest in the field and the minor negative effects of Bt crops demonstrated in the field pale in comparison to alternative pest suppression measures based on insecticides. The use of Bt maize and cotton throughout the world has been associated with an estimated 136.6 million kg global reduction in insecticide active ingredient between 1996 and 2006 (29.9% reduction). Benefits vary by country and region and are heavily weighted towards cotton production, which has historically been one of the largest users of insecticides in the world. New Bt crops and new versions of existing crops continue to be developed. Technical Abstract: Bacillus thuringiensis (Bt), a bacterium capable of producing insecticidal proteins is ubiquitous in the environment, and the genes coding for these proteins are now becoming ubiquitous in major crop plants via recombinant DNA technology where they provide host plant resistance to major lepidopteran and coleopteran pests. In 2007, Bt maize and cotton were commercially produced on a total of ˜38 million hectares in 20 countries. Assessment of environmental safety continues to be a key element of transgenic crop technology. This review focuses on two environmental elements, effects on non-target organisms and changes in insecticide use patterns. Meta-analyses of the extant literature on invertebrate non-target effects reveals that the pattern and extent of impact varies in relation to taxonomy, ecological or anthropomorphic guild, route of exposure, and the non-Bt control against which effects are gauged. Hazards identified in the laboratory may not always manifest in the field and the minor negative effects of Bt crops demonstrated in the field pale in comparison to alternative pest suppression measures based on insecticides. The efficacy of Bt maize and cotton against major pest species has been associated with an estimated 136.6 million kg global reduction in insecticide active ingredient used between 1996 and 2006 (29.9% reduction). Benefits vary by country and region and are heavily weighted towards cotton production, which has historically been one of the largest users of insecticides in the world. |
