GM cotton fails to improve biodiversity or yield (5/8/2006)

Here's another hammer blow for the hyping of GM cotton as a miracle crop: a large scale study showing no benefits for biodiversity, no yield increases, no reductions in herbicide use, and increasing problems with secondary pests.

In 1999 Professor David Baulcombe, now head of the prestigious Sainsbury Laboratory in the UK, told a public meeting that US government research had shown that GM crops brought "enormous environmental benefits, benefits of biodiversity". In support of these claims he referred to a report by the U.S. Environmental Protection Agency (EPA) which was "to be released shortly."

According to Prof Baulcombe, the report showed "an increase in the diversity of insect life; there has been a corresponding increase in the diversity of small mammal life and a corresponding increase in the diversity of birds of prey in those areas of the United States."

No such report was ever published, but Prof Baulcombe was only tarting up as offficial one of the most fundamental and oft repeated claims of GM proponents, particularly in relation to Bt cotton.

Seven years later the study detailed below shows that after a decade of growing GM cotton there is no evidence at all that it is benefitting biodiversity. And this is not the only damaging finding to emerge from this paper published in Proceedings of the National Academies of Science.

This first large-scale study that simultaneously examined how growing Bt cotton affects yield, pesticide use and biodiversity shows there was no increase in yield and no reduction in herbicide use with GM cotton. This was the case even when the GM cotton was a herbicide resistant variety, ie of the sort that is promoted as reducing herbicide use.

And even though the study did show a reduction in pesticide use with Bt cotton and the use of more precisely targeted chemicals, the use of these targeted pesticides was found to rise during the second year of the study. One of the researchers comments, "One thing I was a bit surprised to find is that if you control some pests with [transgenic] cotton, others become more of a problem." (see below)

This, of course, is exactly the pattern found in the recent Cornell study of the long-term effects of Bt cotton cultivation in China. In that case after seven years of Bt cotton production, pesticide use on Bt cotton was more or less equivalent to pesticide use on conventional non-Bt cotton, even though Bt cotton seeds are costing farmers 3 times as much! (Bt Cotton in China Fails to Reap Profit After Seven Years) http://www.newswise.com/articles/view/522147/


Despite Pesticide Reductions, Transgenic Cotton Fails to Improve Biodiversity
David Biello
Science and Technology at Scientific American.com

Genetically modifying cotton promises to reduce the use of chemicals and, potentially, create a better environment for harmless insects and other animals. For the last decade, some farmers in Arizona have been planting cotton engineered to contain a toxin that kills pests such as the pink bollworm. A study of randomly chosen cotton fields reveals that although this genetically modified cotton did reduce pesticide use, it did not reduce use of herbicides nor did it improve biodiversity when compared to unmodified strains.

Ecologist Yves Carriere of the University of Arizona and his colleagues randomly selected 81 cotton fields--split between unmodified and transgenic cotton breeds--over the course of two growing seasons. The scientists gathered data on pesticide use, herbicide use and all the ants and beetles they could find in pitfall traps placed in the fields, as well as other information. "The idea here is to look at not only the possible effects of transgenics but also all the other factors," Carriere says.

The data confirmed that farmers applied pesticides less often to transgenic fields--and used more precisely targeted chemicals when they did. But use of such targeted pesticides on modified cotton did rise in the fields selected during the second year of the study, perhaps due to the need to control pests unaffected by the engineered toxin, the authors speculate. And herbicide use remained the same no matter whether the cotton in question was unmodified, toxin-producing, or toxin-producing and herbicide resistant. "My guess is that they use herbicide resistance as more of an insurance policy," Carriere says.

Nor did genetic modification seem to have an effect on ant and beetle biodiversity; no matter which type of cotton was grown, ant populations declined and beetles boomed in farmed fields compared to adjacent unfarmed fields. Other factors such as soil type, seeding rates and amount of rain played a bigger role in determining population dynamics, according to the paper in Proceedings of the National Academies of Science.

The researchers will continue to refine their analysis of the data, looking for differing impacts on predatory and plant-eating insects as well as an economic analysis of the costs and benefits of genetically modified cotton. "You cannot simply assume that you will get across-the-board benefits," Carriere notes. "One thing I was a bit surprised to find is that if you control some pests with [transgenic] cotton, others become more of a problem."

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