Brussels, Feb 2006
A consortium led by the Commission's Joint Research Centre (JRC) has published new case studies for the effective coexistence of genetically modified (GM) and non-GM crops and seeds, based on novel, real-world computer models.
The report suggests how farmers can reduce the adventitious (unintended and unavoidable) presence of GM material in non-GM harvests on a regional scale, through simulations based on actual agricultural landscapes, weather conditions and agricultural practices.
The research focused on the seed and crop production of maize, sugar beet and cotton. As the only major GM crop approved for cultivation in the EU, maize is a particular priority for coexistence research. For each variety, the report identifies the key sources of adventitious GM material in non-GM crops, estimates the levels of adventitious GM material in the final harvest, based on different farming practices, and proposes effective agricultural measures to reduce adventitious presence to desired thresholds.
For conventional maize crops, the report identifies three main sources of adventitious GM material: traces of GM seeds in non-GM seed supplies, cross-pollination from neighbouring GM fields, and the sharing of harvesting machinery between GM and non-GM fields.
Through simulations to assess the impact of cross-pollination, the researchers found that two variables related to the agricultural landscape have a major effect - the relative position of GM and non-GM fields with respect to dominant winds, and the relative sizes of neighbouring GM and non-GM fields. The best ways of avoiding cross-pollination are through the introduction of isolation distances between GM and non-GM fields, sowing buffer strips of non-GM maize around GM fields, and using GM varieties with different flowering dates to non-GM crops.
Based on the simulations, the report provides 'decision tables' for farmers to determine the necessary isolation distances required to keep adventitious presence below certain thresholds for different field sizes and wind orientations. Overall, the report concludes that achieving 100 per cent compliance with the EU's current 0.9 per cent threshold for adventitious GM presence in non-GM maize crops is possible, but may require the introduction of additional measures, particularly when GM and non-GM crops are grown together in the same 'cluster' around a single water supply point.
For maize seed production, meanwhile, cross-pollination is considered the only source of adventitious GM presence, however there are two scenarios to be considered - coexistence between GM and non-GM seed fields (seed-seed coexistence) and between non-GM seed fields and neighbouring GM crop fields (seed-crop coexistence).
The report concludes that achieving a 0.5 per cent threshold for seed-seed coexistence would require no significant changes to current production methods, while achieving a 0.3 per cent threshold would call for some additional measures, for example taking into account dominant wind directions or increasing current isolation distances. However: 'A 0.1 per cent threshold is not obtainable in practice under these conditions,' concludes the study. Without the introduction of isolation distances of 400 to 600 metres, ensuring seed-crop coexistence is difficult to achieve even for a 0.5 per cent threshold, warns the report. This effectively means that GM maize crops should be excluded from areas of non-GM seed production.
The report concludes that with the use of such novel simulation models, it is now possible to estimate the levels of adventitious GM presence in non-GM production for multiple fields and sources over extended time periods, and to propose and test numerous coexistence measures designed to mitigate them. 'Model simulations are not a substitute for field experiments, but a way of overcoming the limitations (time scale, spatial coverage, costs) inherent to field work,' it ends.