Mixed harvest. The largest trial yet of GM crops yields conflicting news about their impact on wildlife.

GM Crops' Effects on Wildlife Mixed

The most ambitious ecological experiment with genetically modified (GM) crops has both bad and good news for wildlife. Compared to fields growing conventional crops, those planted with GM varieties of beet and oilseed rape (canola) have fewer weeds--which is a goal of genetic engineering. But they also have fewer insects and other invertebrates, an unintended consequence that some fear might disrupt surrounding ecosystems. GM corn, meanwhile, increases the abundance of weeds and bugs. Although the findings apply only to the United Kingdom, they are winning praise as an example of environmental impact assessment. "This is a landmark effort," says ecologist Allison Snow of Ohio State University.

GM crops are one of the most contentious issues in Europe. To help decide whether to recommend that the European Union approve the crops for commercial planting, the U.K. government commissioned three studies. Two have already been released; one found little risk to human health, while an economic analysis indicated that there might be future benefits to consumers and farmers. The final, long-awaited study investigated how wildlife might be affected by crops genetically modified to resist herbicides. This engineering allows farmers to spray herbicides that would otherwise damage the crops.

A large group of government researchers from the Centre for Ecology and Hydrology in Merlewood, Rothamsted Research, and the Scottish Crop Research Institute designed a trial that would pit three GM crops against conventional counterparts in some 60 fields across the country. For beet and oilseed rape, plots with GM varieties had one-third or less the weed biomass of plots of regular crops. In turn, there were fewer bees and other insects that feed upon weeds or their flowers or seeds. The margins of GM oilseed rape plots, for example, had 24% fewer butterflies. Exactly the opposite was true for maize. The portion of fields planted with GM maize had 82% more weeds than conventional corn, because the herbicides used were not as effective. Insects did better too.

Although GM beets and oilseed rape may harm wildlife, it's difficult to predict the overall impact of GM crops from the findings, described in eight papers published today in the Philosophical Transactions of the Royal Society. Wildlife is greatly affected by other aspects of farm practices, such as crop rotations, says study coordinator Les Firbank of the Centre for Hydrology and Ecology. Moreover, the damage from planting a GM variety is no greater than the difference between planting various types of conventional crops.

The findings now go to the U.K. Advisory Committee on Releases to the Environment, which will pass on recommendations about crop approval to the government by the end of the year.

With reporting by GRETCHEN VOGEL

Related site
Information about the trials