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Bt plants: unintended impacts on non-target organisms

Risk assessment for Bt plants: two concepts

Before a Bt plant is released, and especially before it is authorised for commercial cultivation, tests have to be carried out to check that this will not be associated with any harmful impacts on non-target organisms. The authorisation decision is not always easy for the authorities responsible. On the one hand, they have to reach a result within a reasonable amount of time, while on the other they have to take into account complex ecological relationships.

The first genetically modified Bt maize variety was authorised in the USA over ten years ago. Now Bt maize and Bt cotton are grown on more than twenty million hectares worldwide, and the area under cultivation is expanding. With other plant species too, scientists are looking at ways of using the Bt concept to control harmful grazing insects. But again and again there are discussions about whether the Bt toxin produced in the plant has an effect on other organisms as well as the pest it is designed to control.

In different cultivation regions, different non-target organisms come into contact with the Bt plants and the Bt toxin they produce. Do we need separate research for each crop and the non-target organisms that might be affected by it? Or is it possible to develop suitable standard tests that can be applied effectively and that still deliver comprehensive, reliable results? In the field of biological safety research, this discussion has already begun.

GMO Safety spoke to Angelika Hilbeck and Jörg Romeis. These two scientists work in Switzerland. They represent international working groups dealing with the development of suitable models for the ecological risk assessment of Bt maize on non-target organisms.

Jörg Romeis , Agroscope Reckenholz-Tänikon Research Station (ART)

Standard tests with representative organisms: Jörg Romeis’s international working group is proposing a step-by-step process. It is based on a sequence of laboratory, semi-field and field experiments. The approach follows the globally established methods for environmental testing of toxic substances and pesticides.

The focus of the research is on standardised tests in the laboratory with various ‘representative organisms’ selected according to a range of criteria. In the laboratory, toxic effects can be identified in a targeted manner and with a high level of statistical confirmation. If the lab tests provide indications of harmful effects, more investigations are carried out and, if necessary, field trials as well. With this approach it is possible to reduce the need for expensive field trials. In some cases they can be avoided altogether.

Angelika Hilbeck, Institute of Integrative Biology of the Swiss Federal Institute of Technology (ETH) Zurich, and Managing Director of Ecostrat GmbH (Zurich/Berlin).

Studying the most important organisms in an ecosystem: Angelika Hilbeck’s international working group is advocating a much broader approach. It believes the existing ecotoxicological test methods are inadequate, especially for regions with high biodiversity. In her opinion, the standardised approach with selected ‘representatives’ in the laboratory does not provide enough information to be able to make assertions about effects on biodiversity in the ecosystem. Before a test is conducted in the laboratory, the most important non-target organisms with key ecological functions for the ecosystem in question need to be identified. Laboratory tests are then carried out on these organisms and supplemented by field trials.