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The burden of proof: A response to Rosi-Marshall et al.

February 19, 2008
105 (7) E9
To the Editor: A recent paper in PNAS (1) purports to show that insect-resistant crops have unexpected effects on nontarget insects in streams. A sentence in the Abstract reads “Stream insects are important prey for aquatic and riparian predators, and widespread planting of Bt crops has unexpected ecosystem-scale consequences.” The data presented in the paper do not support this statement.
Because previous studies reported no significant effects on caddisflies (2), the topic of the present study leads the reader to reconsider the issue. However, the authors of the recent paper made fundamental errors in experimental design that make it impossible to draw the conclusion that Bt crops have impacts on aquatic insects: (i) They failed to use proper control materials, which would have to have been isogenic, nontransgenic tissues. It is well known that the chemical composition of leaves varies widely between different maize genotypes. It is possible that the claimed negative impacts on larval growth were attributable to chemical components in the tissue and not to the Bt protein. (ii) They failed to identify and to quantify the Bt protein, other leaf chemicals, and agricultural chemicals in stream waters, making it impossible to repeat the study or to draw conclusions from the data.
Publications that report studies lacking appropriate controls and include unfounded summary statements on a topic such as this can cause significant damage. It is unfortunate that this paper, like the previous claim of effects on Monarch butterflies (3, 4), is being used to fuel the contentious debate over the safety of genetically modified crops.

References

1
EJ Rosi-Marshall, et al., Toxins in transgenic crop byproducts may affect headwater stream ecosystems. Proc Natl Acad Sci USA 104, 16204–16208 (2007).
2
TR Glare, MO O'Callahan, Bacillus thuringiensis: Biology, Ecology and Safety. (Wiley & Sons, New York), pp. 47 (2000).
3
JE Losey, LS Raynor, LE Carter, Transgenic pollen harms monarch larvae. Nature 399, 214 (1999).
4
RL Hellmich, et al., Monarch larvae sensitivity to Bacillus thuringiensis-purified proteins and pollen. Proc Natl Acad Sci USA 98, 11925–11930 (2001).

Information & Authors

Information

Published in

The cover image for PNAS Vol.105; No.7
Proceedings of the National Academy of Sciences
Vol. 105 | No. 7
February 19, 2008
PubMed: 18218775

Submission history

Published online: February 19, 2008
Published in issue: February 19, 2008

Authors

Affiliations

Roger N. Beachy [email protected]
Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO 63132;
Nina V. Fedoroff
Science and Technology Adviser to the Secretary of State, U.S. Department of State, Washington, DC 20520;
Willaman Professor of Life Sciences and Evan Pugh Professor, Pennsylvania State University (on leave), University Park, PA 16802;
Robert B. Goldberg
Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA 90024; and
Alan McHughen
College of Natural and Agricultural Sciences, University of California, Riverside, CA 92521

Notes

To whom correspondence should be addressed. E-mail: [email protected]

Competing Interests

The authors declare no conflict of interest.

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    The burden of proof: A response to Rosi-Marshall et al.
    Proceedings of the National Academy of Sciences
    • Vol. 105
    • No. 7
    • pp. 2255-2751

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