A systematic review of the environmental impacts of GM crop cultivation as reported from 2006 to 2011

The current generation of genetically modified crops have shown potential to enhance agricultural productivity and alter farm production economics, but there remains global divergence in adoption of the technology due in part to uncertainty in the underlying science. In an attempt to address this, a systematic review was undertaken, which asked the question “What are the environmental impacts of the global cultivation of GM crops?” A database search statement generated over 19000 hits, which distilled down to 28 articles from which data was recovered to generate a set of R values, where R was the ratio of the GM divided by the conventional field data. Meta-analysis of this data indicated that under GM R had significantly increased from a background level of 1 to a mean value of 1.31. This increase in R, although positive, is not indicative of an environmental benefit due to the difficulty in assigning either benefits or disadvantages to the many indicators that were encompassed within the review. Subsequent regression analysis indicated that there was no standard model to explain the observed variation in R values. However, in models for both cotton and maize, variables relating to the design of the study had a significant effect, but these variables were not related to trait or gene insertion and were generally either year, country or change in cultivation practice in origin. Narrative analysis of the authors published interpretations indicated GM had no adverse effects in 85% of papers, 10% reported a beneficial effect and only 5% a deleterious impact. The conclusion of this study is that GM adoption has had an impact on its environment, but that the underlying cause of this impact is not due to the genetic modification and the effect on the environment is generally seen as not being adverse.