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Where's the science? Assess Bt maize before approval

Eliana Fontes, in her policy brief  'A healthy mix: strategies for GM and non-GM crop coexistence', raises an important question about the sustainability of genetically modified (GM) crop farming.

The question is particularly relevant to Brazil, where a national committee on biosafety is meeting this week (11 June) to decide on the commercial release of transgenic, insect-resistant Bt maize.

The Brazilian constitution makes clear the need to evaluate the biosafety of proposed GM organisms under national conditions before they are commercialised. But, as yet, there has been no scientific assessment of Bt maize under Brazilian conditions, and this should be made a priority before the committee makes its decision.

Unfortunately, parts of the Brazilian media — for example the Journal Folha de São Paulo — are using Fontes' policy brief to promote the benefits of coexistence without giving equal weight to the very real risks of growing GM crops.

Such risks include drift damage, loss of biodiversity, decrease in soil fertility and contamination of wild relatives and pollinators.

The effect of imposing a GM monoculture model on local and indigenous cultivars would be particularly devastating in Brazil, where varieties have long contributed to agriculture and provide an irreplaceable pool of genes for conventional plant breeding.

Substituting their genetic variability with single GM varieties will increase susceptibility to pests and diseases and could result in the loss of many as yet undiscovered useful genes. The rust resistance and dwarf genes in wheat that led to the green revolution were both found in old landraces.

In particular, the use of Bt crops, such as the maize variety under discussion, can lead to the secretion of toxins that destroy nitrogen-fixing bacteria. Moreover, Bt genes could contaminate local crop relatives, reduce the number of natural pollinators and predators, or accidentally enter the food chain and cause allergic — possibly even fatal — reactions in people.

The national committee must ensure a balanced evaluation of the benefits and risks that Bt maize poses for Brazil, based on scientific fact rather than media supposition.