Dec 7, 2005

Research Results

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Bt Maize: Effects on non-target organisms

“Any Bt effects that may exist are extremely minor.”

Bt maize is already grown in several European countries. Many people fear that this genetically modified maize could harm other organisms and have a detrimental effect on biodiversity. An association comprising eleven research projects has been considering these questions over a three-year period. GMO Safety discussed the findings with the association’s coordinator Ingolf Schuphan from RWTH Aachen University.

GMO Safety: One of the fundamental questions facing the research association which you coordinate concerned the potential effects of Bt toxin on “non-target organisms”. Let’s look at fauna that is found above ground first, such as butterflies, beetles, spiders, cicadas and many others. Have you found any differences between Bt maize and conventional maize with or without the use of insecticides?

Schuphan: We found the most significant effects on non-target organisms in the conventional variant, in other words in plots where insecticides were used to control the European corn borer. No appreciable differences were found when comparing Bt maize with the isogenic strain. In one year we did indeed find significant differences between the isogenic and the Bt maize variants, but the following year it was just the reverse. Examples like this indicate that climatic influences, for example, are clearly far more serious than the question of whether Bt or conventional maize is grown. We conclude that if the Bt toxin does have any effects, then they are random and at the limits of detection. Such considerations really need more long-term consideration – not three years like we had, but five or ten.

Of course, all arable farming has an effect on biocoenosis. This is why you have to compare current standard practice with the Bt concept. The result is clear: Bt maize actually only harms organisms which eat maize and thus cause damage. This degree of specificity is currently found nowhere else in plant protection.

GMO Safety: I understand that your research association also studied the entire food chain, so not just those animals which live directly on and from maize, but their predators as well.

Schuphan: Yes, these investigations were not very straightforward, because there are complex interactions going on not just between pests and beneficial organisms but also with animals at the next level, the hyperparasites. But here too the picture was the same: We have found no statistically confirmed evidence in support of Bt effects.

GMO Safety: And what was the situation for organisms living in or on the ground?

Schuphan: Here too we were unable to find anything unusual. The results for soil are similar to those for the herb layer. They also varied from one year to the next.

Within our research association we considered whether the Bt toxin – if it were to accumulate in the soil – would have any effect on certain organisms. One project, for example, worked with sciarid fly larvae; these are organisms that break down straw, in other words dead organic material. During feed trials in the laboratory, effects were observed for one of the two Bt maize varieties under investigation, but they could not be definitely attributed to the Bt toxin.

GMO Safety: Does Bt toxin actually accumulate in the soil?

Schuphan: If good agricultural practice is followed, then we don’t envisage an accumulation of Bt toxin in the soil. It is after all a protein, which is also present in plant residues. If maize straw is ploughed back into the soil after harvesting, Bt toxin can accumulate in the soil in the short term – particularly if there is no crop rotation and one area is continually replanted with Bt maize. This scenario requires extensive research over a period of several years. This is in fact in the pipeline.

GMO Safety: You have coordinated an association comprising several research projects, which investigated other issues including the potential effects on farm animals which were fed Bt maize.

Schuphan: We examined the micro-organisms in the rumen or intestine of dairy cows which had been fed Bt maize for evidence of genetic material from Bt maize. We found no indication of this type of horizontal gene transfer, in other words of the transfer of genes from Bt maize.

The Bt toxin is rapidly broken down into protein fragments inside the cow’s intestine. Bt maize behaves exactly like conventional maize in a dairy cow. It goes without saying that no gene or toxin from the Bt maize is transferred to the milk. If this were the case, we would find a complete mishmash of genes or genetic products from buttercups, grasses and herbage in our milk.

GMO Safety: One of the association’s tasks was to identify potential organisms which would be suitable for post-market monitoring. These could be certain species that are particularly sensitive to the Bt toxin and could act as a kind of early warning system. Have you been able to find any such species?

Schuphan: Well, for a start, our findings indicate that monitoring isn’t actually necessary, since no harmful effects of Bt maize were actually detected. If monitoring were required, the most likely candidates would be those species at the bottom of the food chain, for example cell content feeders like leafhoppers or thrips and also their antagonists, the predatory bugs from the genus Orius. In the case of ground-dwelling organisms it would be a predatory spider and common species of ground beetle such as Pterostichus melanarius and Pseudophonus rufipes.

GMO Safety: How many organisms have you and your group in Aachen actually collected and identified?

Schuphan: In our project alone we have collected, classified and identified almost half a million organisms over three years. If you take into account the other projects in our research association, then almost one million creatures have passed through our hands. This has been an extremely complex operation when you think that most of the species cannot even be identified with the naked eye.

GMO Safety: So your findings are supported by an astonishingly broad and comprehensive database.

Schuphan: Well, that’s how I see it, too. Our research association was made up of eleven partner institutions, five or six of which were concerned with non-target organisms. After three years of investigations we can safely say: If there are any Bt effects on agrobiodiversity, they are random and at the limits of detection. Over the years they balance out again.

GMO Safety: Thank you for talking to us.