Bt cotton no risk to the environment?
In a two-year study of extensive cotton fields in Arizona, researchers found no negative effects of genetically modified crops on their environment. Crop yields were about the same as non-manipulated cotton, but farmers were able to use fewer insecticides.
Yves Carrière from the University of Arizona in Tucson and his colleagues examined 81 cotton fields covering a total of 6,600 square kilometers and compared the yield and use of pesticides with those of 40 fields of conventional cotton. They also recorded the diversity of ants and beetles in neighboring, uncultivated areas. In doing so, they wanted to demonstrate a potentially deleterious effect on beneficial species that are inadvertently killed by the toxin produced in the leaves of the engineered plants.
Proximity to a Bt cotton field was not among the factors that influenced the biodiversity of these insects, according to statistical analysis, Carrière and his collaborators report. Instead, environmental conditions such as the sand content of the soil, the use of broad-spectrum insecticides or the density of the seed are decisive.
Bt cotton contains a gene from the soil bacterium Bacillus thuringiensis, the gene product of which is toxic to certain harmful organisms. So far it has not been clarified whether this poison also has a negative effect on other living beings that are not the target of the defense - research results on this are contradictory. There are also fears that the gene could cross into wild forms and thus spread uncontrollably.