Do GM crop plants threaten biodiversity and the environment ?

GM crops are questioned as to their impacts - actual or potential, direct or indirect - to the biological communities of field and wild environments. The scientific assessment of these questions is highly complex, both from a methodological point of view (where and how to gather the relevant information ?) and for the interpretation and use of the data (how can we transpose the data from one geographic area to another, from laboratory or field experiments to commercial releases ?). At the same time, it is a hot topic in the GM debate and a challenge for the regulatory authorities in charge of the environmental risk assessment (‘ERA’). One way to answer is to look at the current situation after ten years of GM crop cultivation, on millions hectares worldwide. As concluded  by a recent (2006) and  authoritative report of the Swiss Expert Committee for Biosafety (http://www.art.admin.ch/dms_files/03017_de.pdf), reviewing mainly peer-reviewed scientific literature and reports form international organizations, “the data available up to now do not provide any scientific evidence for harm caused to the environment by commercial cultivation of GM crops”.

Nevertheless, current applications are restricted to only a few traits and it is essential to bear in mind that ERA needs a step wise, case-by-case study of each trait/plant/environment combination. ERA addresses both the adverse effects on non target organisms and the invasiveness of the GM plants and their possible progenies, including potential hybrids with wild relatives. Laboratory and field trials have been systematically conducted on the current commercial traits. Although harmful effects have incidentally been demonstrated in artificial conditions, like the toxic potential of Bt-pollen fed to Monarch butterfly larvae, the ecological risk, pertaining to the probability of the harm in the actual field environment was concluded as very low, hence acceptable in comparison with the existing crop protection practices (insecticide application). Understanding the difference between hazard and risk is thus essential.

In order to evaluate the environmental safety of herbicide-tolerant GM plants, accounting for more than ¾ of the GM crop areas, a farm scale evaluation was conducted in UK, monitoring the populations of non target organisms throughout the food chain, in three successive years of cultivation of HT oilseed rape, sugar beet and maize(http://www.defra.gov.uk/environment/gm/fse/). As a conclusion, a reduction of biodiversity was observed with oilseed rape and sugar beet, but an increase was noticed in maize. This emphasizes that no general conclusion can be drawn, even within the same trait. As the reduction of biodiversity was related with the efficiency of weed control, the data were in fact not much surprising. In addition, for assessing the ecological impact of engineered herbicide tolerance, a different cropping scenario could have been chosen, like reduced tillage which results in greater availability of crop residues, supplying more food to insects and their predators, hence impacting biodiversity in a positive way.

back