Resolutions
Environmental Protection Agency's (EPA) Approach
Case Closed. The verdict: Bt corn poses a "negligible" threat to monarch larvae
Conclusions
Environmental Protection Agency's (EPA) Approach
Losey's and Obrycki's publications resulted in heated debates over the effects of Bt corn, amongst activist groups and academic scientists. Opponents of GM foods, such as Greenpeace, Friends of the Earth, and Environmental Defense, demanded that the U.S. Environmental Protection Agency (EPA) cancel Bt corn's registration/permit. (Ament, 2000) In December of 1999, the EPA requested industry, researchers, and all interested parties to submit information and comments about the Bt /Monarch controversy by March 2001, in order to reevaluate the risks before the reregistration of Bt corn when its old permit expired on September 30th. (Sears et al., 2001) and Pollack, 2001). The EPA and the agricultural biotechnology industry financed several studies performed by academic scientist, addressing whether the effects previously observed in the laboratory are relevant to the field. (Pollack, 2000)Back to top
Controversy Resolved: Bt corn poses a "negligible" threat to monarch larvae
Several scientists, including Losey and Obrycki, collaborated in comprehensive research projects to determine the real effects of Bt corn on monarch butterflies. A package of six papers was submitted to the Proceedings of the National Academy of Sciences for September 14th publication. The papers were initially intended to be published in the October 1st issue, but the EPA asked the journal to publish the papers earlier, so that the public could review the new research findings before the EPA made its announcement to reregister Bt crops. (Reuters, 2001 and ARS Website, 2004 )
The papers, reflecting 2 years of research, suggest 4 reasons why Bt corn poses a negligible risk (hazard + exposure) to monarch larvae (Sears et al., 2001):• Most commercial Bt corn plants express low levels of Bt toxin in their pollen, and laboratory and field studies show no acute toxic effects at any pollen density that would be encountered in the field.
• There is variable and limited overlap between pollen shed and larval activity periods.
• Only a fraction of the monarch population utilizes milkweed plants in or near cornfields.
• Only 19% of North American corn is modified with the Bt gene.
(Sears et al., 2001 and ARS Website, 2004)
Monarch larvae feeding on milkweed leaf
Photo Courtesy of Peggy Greb,
ARS image gallery
Research did find that one commercial Bt corn plant - Event 176 - did express the toxic Cry1Ab protein in its pollen at high enough levels to have detrimental effects on monarch larvae. Event 176 uses a different promoter than other commercial Bt plants, such as Mon810 and Bt11, resulting in 40-fold higher concentrations of toxins.(Gatehouse et al., 2002) However, Event 176 – marketed as ‘Knockout' – was so unpopular with farmers at the time that it constituted less than 2% of crops planted, and was withdrawn by its manufacturer, Syngenta. (Clarke, 2001)
Despite pressures from GMO opponents, the EPA renewed its Bt corn registration in October of 2001, after acknowledging that the transgenic crop posed negligible risk to monarch butterflies. The registration allowed companies to sell Bt corn for seven more years. The EPA also added new safeguards into their crop registrations, including the requirement that seed companies monitor Bt crops to detect any insect resistance and teaching farmers how to use buffer zones around Bt crops. (Reuters, 2001) The EPA decision ended an exhausting dispute over the Bt corn/monarch butterfly controversy. Environmental groups were disappointed with the decision.
Although the initial claim by Losey et al. that transgenic pollen harms monarch pollen turned out to be a bit misleading, the Bt/butterfly controversy gave a whole new perspective on GM crops. (Clarke, 2001) It demanded that scientists and policy-makers carefully examine all potential effects of biotechnology/agro technology non-target organisms and on the environment before introducing it to industry.
While the question of whether Bt corn pollen alone poses a significant threat to monarch butterfly larvae has been answered, still other questions remain about the genetically modified crop. (ARS Website, 2004 ) For instance, when will the target insects develop resistance to Bt toxins? and are there other non-target organisms that have not even been considered yet? New questions arise everyday about genetically modified crops. Hopefully the Bt/butterfly controversy of 1999-2001 encouraged researchers to do extensive research in order to answer these important questions, while GM crops are on the rise.
Contact me: Leigh Anne Hoskins, lehoskins@davidson.edu
Last modified on 11 February, 2004
________________
