Trials 'Underestimate GM Crop Risk'
June 01, 2007
Field trials could be underestimating the potential for cross-pollination between GM and conventional crops, according to academics.
Research by a University of Exeter research team in Devon has recommended a new method for predicting the potential for cross-pollination, taking account of wind speed and direction.
The research was funded by the Natural Environment Research Council and is published in the journal Ecological Applications.
The team used records of wind speed and direction from weather stations across Europe to predict the movement of pollen in the air.
The findings showed huge variation in the amount of cross-pollination between GM and non-GM crops of maize, oilseed rape, rice and sugar beet.
Levels varied according to whether the GM field was upwind or downwind of the non-GM field, given the direction of the prevailing wind over the flowering period of the crop.
Field trials are regularly carried out to measure the potential for cross-pollination between GM and conventional crops.
Current guidelines for minimum field-to-field distances are based on the results from these trials.
However, if the GM field in a trial is downwind of the non-GM field, the trial will underestimate the potential for cross-pollination.
The research resulted in the development of a theoretical computer model to analyse the effects of wind on pollen travel.
The Effect of Wind Direction on Cross-Pollination in Wind-Pollinated GM Crops
Ecological Society of America
By Martin Hoyle and James E. Cresswell, School of Biosciences, University of Exeter, Exeter EX44PS UK
Volume 17, Issue 4 (June 2007)
Ecological Applications: Vol. 17, No. 4, pp. 1234-1243.
In Europe, regulatory thresholds restrict adventitious GM (genetically modified) presence in conventional crops. Minimum distances for the spatial separation of fields are often recommended to reduce field-to-field cross-pollination to an acceptable level. Field trials are typically the basis for setting separation distances. However, using records of wind direction and speed from weather stations across Europe, we predict theoretically that field-to-field windborne cross-pollination in maize, oilseed rape, sugar beet, and rice varies greatly according to the relative orientation of the GM and non-GM fields. Furthermore, at a given site and orientation from a GM field, we predict that the cross-pollination rate varies substantially from year to year. Consequently, even replicated field trials may inaccurately estimate typical levels of cross-pollination and therefore distort our perception of the separation distances required to achieve sub-threshold adventitious GM presence. We propose methods to predict the likely range in levels of cross-pollination based on the limited data typically available from field trials. Additionally, we suggest suitable time lags between peak flowering in adjacent fields that could be introduced to reduce cross-pollination to a specified level.