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In the context of agriculture and food and feed production, co-existence means using cropping systems with and without genetically modified organisms (GMOs) in parallel. For co-existence to be assured, the separation and the identity of the respective food and feed products must be maintained at all stages of the production process. The goal of co-existence is to allow all farmers to choose whether or not to grow GMOs, and to let consumers exert market pressure by accepting or rejecting GM foods when making purchasing decisions.

Contents 1 Reasons for co-existence 2 Problems of co-existence 3 Measures for ensuring co-existence 3.1 Biological approaches to aid co-existence 3.2 Research on co-existence 4 External links

Many consumers are critical of genetically modified plants and their products, while, conversely, most experts in charge of GMO approvals do not perceive concrete threats to health or the environment. The compromise chosen by many countries has been to implement co-existence and traceability. Traceability has become commonplace in the food and feed supply chains of most countries in the world, but the traceability of GMOs is made more challenging by the addition of very strict legal thresholds for unwanted mixing.

Mixing can occur already at the agricultural stage. Fundamentally, two reasons exist for the presence of GMOs in the harvest of a non-GM cultivation: first, that the seed has been contaminated already or, secondly, that the plants in the non-GM field have received pollen from neighbouring GM fields. Since GM-free products yield higher prices in many countries, governments have been obliged to regulate limits for the mixing of both production systems, and to compensate non-GM farmers for economic losses in cases where mixing inadvertently occurred. A common tool for compensation is a liability fund, to which all GM farmers, and sometimes GM seed producers, contribute.

To limit mixing in the first stages of production, researchers and politicians are developing codes of good agricultural practice for GM crops. In addition to the thorough cleaning of machinery, recommended measures include the establishment of "isolation distances" and "pollen barriers". Isolation distances are the minimum distances required between GM and non-GM cultivations for most of the GM pollen to fall to the ground before reaching non-GM plants. Pollen barriers actively catch pollen, and can consist of hedges and trees which physically hinder pollen movement. Pollen barriers consisting of conventional crops of the same species as the GM crop have a special advantage, as the conventional plants not only physically limit the GM pollen flow, but also produce competitive, conventional pollen. During harvest, the buffer strip of conventional crops is considered part of the GM crop yield.

In addition to agricultural measures, there may be also biological tools to prevent the genetically modified crop from fertilising conventional fields. Researchers are investigating methods either to prevent GM crops from producing pollen at all, or to develop GM crops with pollen that nonetheless does not contain the additional, genetically engineered material. Two important research projects on co-existence are SIGMEA and Co-Extra.

While SIGMEA was focused on co-existence at the farm level, Co-Extra studies co-existence along the whole production chain, and has a second focus on the traceability of GMOs, since co-existence cannot work without traceability. To be able to monitor and enforce compliance with co-existence regulations, authorities require the ability to trace, detect and identify GMOs. Without reliable systems for the separation of both production methods, consumers would have little trust in the labelling of GM-free products – which would mean the end of institutional co-existence.

• Co-Extra – EU research programme on co-existence and traceability along the whole production chain
• SIGMEA – EU research programme on co-existence in agriculture
• Transcontainer – EU research programme on biological containment systems for genetically modified plants
• GMO-Compass – facts, numbers, and news about GM crops in Europe