In our country the debate on GMOs has intensified further after as many as 39 organisations joined forces to push the Italian government and public opinion to take a clear stance on biotech crops.

GM plants cultivated worldwide. The majority of genetically modified species grown globally are soya, maize, cotton and rapeseed. According to Dr Manuela Giovannetti, Full Professor at the Department of Agriculture, Food and Agro-environment of the University of Pisa, they amount to approximately 176 million hectares worldwide. These are species used in industry and in the production of animal feed. Their defining characteristics are immunity to herbicides and to pathogenic insects.

The environmental effects. "The debate on GMO safety has been going on since 1998," explains Dr Manuela Giovannetti. "The issue was addressed by well-known scientific journals that were already asking at that time what the environmental effects might be that we would have to face."

1. Transfer of modified genes to soil bacteria

This is one of the problems that the WHO had already raised in 1996, namely "what might the problems for human health be?". Particularly in the early days, microbiologists used DNA fragments capable of producing a certain resistance to antibiotics. It was observed that these fragments passed to soil bacteria and subsequently transferred to pathogenic bacteria, making them potentially dangerous to health. For this reason, the practice was gradually abandoned.

2. Hybridisation between GMOs and wild plants

In technical terms, "outcrossing". This is one of the most feared aspects, namely: "can plants of the same species but non-GMO be contaminated?" The answer is yes. Rapeseed, for example, has a hybridisation radius of as much as 3 kilometres, while for maize the range is from 50 metres to 200–300 metres. The question remains open: "What are the limits of coexistence?".

3. The emergence of super weeds

In this case, contamination occurs between different species (for example, maize and a weed): the fragment carrying herbicide resistance hybridises with the very species one is trying to eradicate. This is what has been and continues to be recorded in various intensive monocultures, where some plants have developed a resistance three times greater than normal. This leads to massive pesticide use.

4. The emergence of super-resistant insects

To resist harmful insects, the DNA of plants has been supplemented with a gene extracted from a particular bacterium, capable of killing the larvae of phytophagous insects. These plants produce a neurotoxin that is lethal to the insects that feed on them. What is the problem? This has caused what is technically referred to as "selective pressure" — that is, the natural selection of insects resistant to the toxin. Farmers now have to create buffer zones planted with unmodified crops in order to reduce selective pressure and consequently "control" the emergence of super-resistant insects.

5. Release of transgenic toxins into the soil

The toxins produced by engineered plants are released through the roots. From the root tissues they pass into the soil, where they remain active for many days after harvest.

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Stewart et al. 2003. Genetic modification: Transgene introgression from genetically modified crops to their wild relatives. Nature Reviews Genetics 4, 806-817.

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Insecticidal toxin in root exudates from BT corn. Nature. Vol. 402. December 1999.