The issue of contradictory results of biosafety studie

The results of biosafety studies on GM crops are often controversially discussed in public debates. Some studies even provide a contradictory picture of the safety of products such as Bt maize.

More importantly, results of such studies are used for the justification of political decisions. For example, the cultivation of the genetically modified MON810 maize was banned in Germany in April 2009, mainly substantiated with two new studies that claim to show that MON810 poses a risk to two-spotted ladybirds and water-fleas, however these studies were scientifically controversial. Similarly justified bans were enacted in Luxembourg, Greece and Austria. In contrast, the European Food Safety Authority (EFSA) recently confirmed its positive assessment of MON810 maize and concluded that non-target organisms, such as insects and water-dwelling organisms, are not at risk.

Michelle Marvier is an Associate Professor at the Environmental Studies Institute, Santa Clara University (USA). Her research is focused on two issues: the ecological risk assessment applied to genetically engineered crops and the conservation of biological diversity. She conducted two renowned meta-analyses on the environmental impact of Bt crops (effects of Bt Cotton and Maize on non-target invertebrates and in particular on honey bees).

Michelle Marvier from Santa Clara University (USA) illuminates the reasons for conflicting study results and new approaches on how to manage such uncertainties and to improve the significance of biosafety research results. She is promoting large open-access databases for biosafety studies and the application of meta-analyses. Such meta-analyses use the results of numerous studies to get a statistically more reliable picture of the environmental impact of GM crops.

GMO Compass: What is your personal motivation to conduct research on the environmental effects of GM crops?

Michelle Marvier: I have always loved growing vegetables in my home garden, and I'm interested in food production and the environmental impacts of agriculture, in general. As a graduate student, I worked on several agroecology projects, sampling beneficial insects in cotton, strawberries, and cabbage. I also really enjoy thinking about experimental design and statistical analysis. So, that combination of interests led me to look a bit more critically at the experiments being used to study potential risks of GM crops.

GMO Compass: Scientific studies seem often to be contradictory. One study reveals that a certain GM crop is harming a non-target organism, another study excludes this. How does this happen? Is this caused by flawed science and inappropriate statistics or by biased researchers?

Michelle Marvier: Actually, given the small sample sizes and high variation that characterize these types of risk assessment studies, it's not surprising at all that different studies yield contradictory results. Many of the studies that have been conducted to look at risk for non-target organisms are "weak." What I mean is this - in the lab, the number of animals exposed to the treatments is typically small and in the field, relatively few plots or fields are used. In contrast, think of a drug trial. When a pharmaceutical company is looking to see whether a drug has side effects, they conduct studies involving hundreds, sometimes thousands, of people. But for GM crops, the studies might involve just a handful of insects or field plots. When studies have low replication, the results are more likely to reflect chance outcomes. So, given this, it should be expected that some studies might show a negative effect and others a positive effect.

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