Agron. Sustain. Dev.
Volume 29, Number 1, January-March 2009
Page(s) 11 - 30
Published online 23 October 2008
Agron. Sustain. Dev. 29 (2009) 11-30
DOI: 10.1051/agro:2008051

Coexistence of genetically modified (GM) and non-GM crops in the European Union. A review

Yann Devos1, Matty Demont2, 3, Koen Dillen3, Dirk Reheul1, Matthias Kaiser4 and Olivier Sanvido5

1  Department of Plant Production, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
2  Africa Rice Center (WARDA), BP 96, Saint-Louis, Senegal
3  Centre for Agricultural and Food Economics, Katholieke Universiteit Leuven, de Croylaan 42, bus 2424, 3001 Leuven, Belgium
4  The National Committee for Research Ethics in Science and Technology, PO Box 522, Sentrum, Prinsensgate 18, 0105 Oslo, Norway
5  Agroscope Reckenholz Tänikon Research Station ART, 8046 Zürich, Switzerland

Accepted 30 July 2008; published online 23 October 2008

Abstract - The adoption of genetically modified (GM) crops in the European Union (EU) raises questions on the feasibility of coexistence between GM and non-GM crops. Regulations to ensure that different cropping systems can develop side-by-side without excluding any agricultural option are currently implemented or developed by member states. The aim of this review is to explore whether nationally or regionally proposed coexistence strategies comply with the general principles established by the European Commission that ask for science-based and proportionate coexistence measures. In the first part, existing legal requirements and potential sources of adventitious mixing are reviewed. It is discussed what type of coexistence measures might be necessary to keep GM inputs below the legal tolerance threshold of 0.9%. Concentrating on cross-fertilisation as the major biological source of adventitious mixing in maize, it is then assessed to which extent available scientific data on cross-fertilisation can explain the diversity of currently proposed isolation distances by several member states. In the second part, it is analysed whether currently proposed isolation distances reflect contending policy objectives towards GM crops that largely exceed the economic scope of coexistence. It is investigated how coexistence is intersecting with a wider debate about the role of GM crops in agriculture. Based on the analysis of existing cross-fertilisation data, it is concluded that some of the currently proposed isolation distances are not in line with the coexistence principles laid down by the European Commission: they are (i) excessive from a scientific point of view; (ii) difficult to implement in practice; (iii) rarely proportional to the regional heterogeneity in the agricultural landscape; and (iv) not proportional to the farmers' basic economic incentives for coexistence. Hence, the range of proposed isolation distances cannot simply be explained by different interpretations of available scientific data, possible error intervals and remaining uncertainties inherent in the scientific process. It is argued that other than scientific issues must be at play. One might thus claim that coexistence has become an arena of contending values and visions on the future of agriculture and on the role GM crops might play therein.

Key words: adventitious mixing / Bt-maize / coexistence / cross-fertilisation / flexible measures / genetically modified (GM) crops / isolation distances  / liability / fixed measures / sustainable development

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© INRA, EDP Sciences 2008