Do genes travel?

Crops that are wind or insect pollinated are more at risk of gene dispersal than self-pollinating varieties, but there is still a significant risk despite this. It is by nature a design of plants to cross pollinate to spread genes further afield.

Maize, oil seed rape, sugar beet, barley, among others, are wind and insect pollinated, allowing pollen to travel large distances. Peas, wheat and beans are self-pollinating normally, although when conditions are favourable these species are also wind pollinated. In some cases the plants must be cross pollinated in order for the seeds to be viable.

In GM crop fields, pollen drift and insect pollination create obvious problems for nearby non-GM or organic crops. Sugar beet, Maize and oil seed rape pollen is light enough to travel long distances. Unfortunately identifying cross contaminated plants is only possible by laboratory testing.

Wheat is a crop of huge commercial importance. Wheat mostly self-pollinates and its pollen is quite heavy, meaning that it does not tend to drift far, but it still can, especially because wheat is a relative of some grasses that can act as recipients for its pollen and this is known as horizontal gene transfer.

Is Prevention Possible?

Because of the inevitability of contamination of non-GM crops with GM pollen, the EU has established recommendations for thresholds of these inevitable contaminations. It also has guidance for buffer zones.

There is currently no need to label products that are contaminated with less than 0.9% of the total marketed product with GMOs (genetically modified organisms). The sources of this contamination could be seed impurity, machine contamination when sowing or harvesting, cross fertilisation and mixing during transport, storage and processing.

At the moment, areas in Europe that grow GM are pretty low, and there are no commercial fields of GM crops in Britain, although the logistics of preventing contamination in America, where GM crops are grown everywhere, is causing farmers major headaches, so Europe is right to approach with caution.

To try to avoid pollen drift and cross contamination, buffer zones can be used. This could be a distance of isolation between GM and non-GM crops, which is a recommended 50m. Alternatively, a buffer zone of crops can be used to ‘catch’ pollen drift. These buffer crops are then either harvested and destroyed, or harvested and marketed at GM because of the contamination.

However, 50m is the bare minimum to allow for the 0.9% contamination levels. Maize pollen for example is regularly found over 180m away from the parent plants, and there are also reports of sugar beet pollen travelling over 12km (8miles) away from parent plants. Oilseed rape pollen is regularly transported 3-4 miles by pollinating insects.

So the 50m buffer zone is hardly conducive to co-existence. It simply becomes an exercise in damage limitation.

Losses made by non-GM and organic farms are a serious issue in many areas where GM crops are grown commercially. Loss of organic status or loss of export trade to non-GM buyers can incur significant commercial losses.

Has there been contamination?

  • A West Australian organic farmer whose crops were contaminated by genetically modified (GM) canola has lodged a writ in the Supreme Court seeking damages for his loss of income. In what could be a landmark case, farmer Stephen Marsh from Kojonup, in the state’s southwest, is taking his neighbour to court after 70 per cent of his farm was stripped of its organic certification in 2010.
  • The large scale cultivation of herbicide-resistant rapeseed in Canada resulted in the contamination of neighbouring fields and crops by genetically modified organisms. Up to 5% of contamination was detected in certified conventional seeds.
  • Crossbreeds of Bt-maize originally grown in the U.S. were found in Mexico. The novel characteristics first turned up in regional maize species and cognate wild plants in 2001.
  • In Costa Rica, where genetically modified seeds of cotton and soy beans have been reared on an experimental level and cultivated for the global market since 1992, transgenic cotton now grows unhampered along bank slopes, field paths and even in front gardens.
  • “It's doubtful whether there’s a farm anywhere in western Canada that does not have Monsanto Roundup Ready canola seed in its soil…. If you have it, you are to call Monsanto and they are to come out and deal with it. How, pray tell, are they going to do this – by plucking out the offending plants one by one – for up to 10 years after each contamination event occurred (canola seed can remain dormant under western Canadian conditions including no-till) – during which time you are disallowed from growing canola because if you do, and volunteer Monsanto canola emerges, sets seed, and shatters, it all starts over again?" Dr. E. Ann Clark, professor of plant agriculture, University of Guelph, "Canadian professor speaks out on Percy Schmeiser decision", Crop Choice,             March 30 2001
  • “The cultivation of genetically modified maize [in Spain] has caused a drastic reduction in organic cultivations of this grain and is making their coexistence practically impossible."Conclusion of research published in the Journal of Agricultural and Environmental Ethics: "An impossible coexistence: transgenic and organic agriculture", Universitat Autonoma de Barcelona, 30 June 2008
  • "In 2006 it was discovered that 30% of the entire US long-grain rice supply had become contaminated by experimental GM rice varieties unapproved for human consumption. Not only was this a public safety disaster, but also cost the rice industry over $1 billion. The contamination source? 'Controlled' field trials." The Soil Association, "Government to defy critics with secret GM crop trials", Today's News, 17 November 2008
  •  A research team found GM seedlings in three traditional maize fields in Uraguay despite a Eucalyptus tree barrier (12 metres high, 30 metres wide) separating the fields, and another case involved cross-fertilisation between fields more than 250 metres apart.

Should we risk it?

In Britain, where farming is a major part of our heritage and trade, contamination is a huge concern. Because we have a relatively small landmass, the feasibility of adequate buffer zones and separation distances is limited. Cases in North and South America, which do have adequate landmasses, show that even this is not sufficient protection (see video GM crops farmer to farmer in video section). The risk to export trade and contamination of organic farms is too great to even contemplate trying coexistence between GM and non-GM crops, and horizontal gene transfer to native/wild species is of massive concern to environmentalists and scientists alike.

The term ‘genetic pollution’ is often used to describe the process of gene transfer, but unlike chemical pollution which can be contained or will disperse with time, genes self-replicate, and are impossible to control once released into the environment.

It is for these reasons then, that field trials and commercial trials of GM crops should be avoided in Britain. The rejection of GM foods and technologies by the general public should be enough of an incentive to focus research elsewhere, or on the more sophisticated method of MAS or Marker Assisted Selection of genes for conventional breeding. One can only assume that the push for GM is purely a commercial one, and this is certainly not a good enough reason to risk  such unpredictable contamination.


  1. Meier, F.C. and E. Artshwager. 1938. Airplane collection of sugar beet pollen. Science 88:507-508.
  2. Global consequences of GM crop cultivation
  3. Journal of Agricultural and Environmental Ethics: "An impossible coexistence: transgenic and organic agriculture", Universitat Autonoma de Barcelona, 30 June 2008
  5. Coexistence of plants and coexistence of farmers: Is an individual choice possible? Binimelis, R., Journal of Agricultural and Environmental Ethics, 21: 437-457, 2008
  7. Galeano, P., C. M. Debat, et al. (2011). "Cross-fertilization between genetically modified and non-genetically modified maize crops in Uruguay." Environ. Biosafety Res.
  8. Can GM and non-GM crops coexist?
    Setting a precedent in Boulder County, Colorado, USA
    P.F. Byrne1* and S. Fromherz2
    Can GM and Non-GM crops coexist? Setting a precedent in Boulder County Colorado USA, P.F Byrne and S.Fromherz