From nature news
Crop management gets vital role in transgenic debate
Genetically modified strains have been evaluated in 'real' farming situations.
Crops that are genetically modified to be resistant to herbicides could make weeds easier to manage without destroying valuable biodiversity. So says the first trial to compare transgenic and conventional crops farmed in rotation.
The four-year study, called
Botanical and Rotational Implications of Genetically Modified Herbicide
Tolerance (BRIGHT), involved five different agricultural researchstations
The scientists found that the number of weed seeds on the plots, a measure of biodiversity, increased over the four years in all cases. This shows, they argue, that although weed plants themselves can be controlled, transgenic crops do not necessarily damage diversity. This partly echoes the message of the British government's Farm Scale Evaluations, the results of which were published last year, but which gave mixed reports as to whether transgenic crops deplete diversity.
BRIGHT also assessed which farming strategies were best at killing weeds. On 50% of study plots, growing oilseed rape that had been engineered to resist the wide-ranging herbicide glyphosate, also called Roundup, gave the lowest weed numbers throughout the four years. Using such rape could make it easier and cheaper for farmers to keep weeds down, the BRIGHT team said at a press conference in
Transgenic crops could potentially represent a cheap option. Weedkillers for conventional oilseed rape cost £60 (US$113) per hectare, compared with £16 for the Roundup-tolerant crop and £40 for a different transgenic strain that is resistant to the herbicide glufosinate, reports Peter Lutman of Rothamsted Research in
The results underline the fact that it is the way the crop is farmed, not the crop itself, that determines its effect on biodiversity. "The impact is not due to the crop, it's due to the management of the crop," says Jeremy Sweet, the project's scientific coordinator.
"This asks for a degree of joined-up thinking about how we govern these crops. It's not just picking a genetically modified crop and saying 'this is good, that one's bad'," Lutman adds.
The BRIGHT team does warn that seeds left over from transgenic sugar beet would be impossible to separate from normal sugar beet grown subsequently on the same land. Farmers would therefore struggle to stay under the 0.9% contamination limit required for a crop to be sold in
The team hopes that European governments will take notice of their work when deciding how to regulate transgenic crops. Despite a recent European Union directive calling on member states to impose regulations on the crops,
But advocates counter that such stringent regulations will foment anti-GM feeling and are unnecessary, citing researchers' claims made at a press conference two days earlier that transgenic corn fields can 'coexist' alongside conventional ones without significant contamination.
Such debates are in danger of missing the point, warns Sweet. Investigators need to take a holistic approach to evaluating biodiversity, he says, rather than simply considering the effect of a single crop strain or weed-killing chemical. "We want people to look at the whole farming system," he says.