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A Dead Good Bug: GE's Impact on Beneficial Insects
Organic farmers have used the Bacillus thuringiensis (Bt) bacteria for years to control certain pests. So-called life sciences companies toot their horns over their successes in incorporating parts of Bt's genetic code directly into the genetic code of certain commodity crops, thereby, they claim, protecting corn, cotton and potatoes from predators. But what they don't tell you is how the genes for Bt that are inserted into the plant's DNA are critically different from the Bt that occurs in nature.
In its natural form, the Bt bacteria contains a long crystallized protein, which must be partially digested in an insect's stomach before it releases the active toxin, which punches holes in the insect's digestive tract and kills it. It is this short toxic form of the protein that has been engineered into plants. However, this active toxin will only be created in the guts of certain insects, and therefore few other organisms have been exposed to it. The effect that the widespread release of the active toxin may have on non-target organisms has not been researched by the producers of Bt plants, but some of the available data is matter for concern.
For example, springtails (Collembola) are flightless insects that feed on fungi and debris in soil and are active decomposers-an essential step in the cycles of the plant ecosystem. A study submitted to the US Environmental Protection Agency indicates that Novartis's Bt corn harmed springtails (EPA MRID No. 434635). Green lacewings are major predators of corn pests. Researchers from the Swiss Federal Research Station for Agroecology and Agriculture found a two-thirds increase in mortality of green lacewing larvae that were fed either European corn borer or armyworm larvae raised on Novartis' Bt corn, as compared to lacewing larvae fed larva raised on non-transgenic corn (Hillbeck et al., 1998). Ominously enough, it did not matter if the lacewings ate prey that had been poisoned by Bt or prey that proved to be Bt resistant. This means that Bt resistant insects could eat Bt corn, then fly away to other plants where they were in turn eaten by lacewings, which would then die. Potentially, the ecological disruptions extend far beyond the transgenic crop plots.
The London Times reported that the lifespan of ladybugs was reduced to half when they ate aphids that had fed on genetically altered potatoes in fields in Scotland. The ladybugs also laid fewer eggs.
In Thailand, where trials of Monsanto's Bt cotton began in 1996, the committee in charge of the field trials was told that 40% of the bees died during a contained trial (Compeerapap, 1997). It is not clear if the bee mortality was the result of Bt cotton since no further information has been made available.
Genetic smog alert
The hydrocarbon economy is still going gangbusters, but there is a new kind of smog to worry about. "Genetic smog" or "genetic pollution" is what happens when genes for traits engineered in the laboratory move into wild or cultivated versions of the same plant or into closely related species.
The dangers of transgenic pollution are not fully understood. Research indicates that the widespread cultivation of herbicide resistant crops would make likely the creation of herbicide resistant "super weeds." Researchers also speculate on the possibility of the transfer of the genes for Bt expression to wild plants, which would seriously disrupt ecological cycles by giving them an advantage over predators that keep them in check.
Life-sciences companies have pooh-poohed such possibilities, downplaying the role "horizontal gene transfer." However recent research has indicated that gene flow between crop plants and their wild relatives may be higher than is normally thought, increasing the risk that engineered gene sequences pass into other plants. Most startling is a report from researchers at Indiana University, who have documented how a genetic parasite previously belonging to the yeast family has suddenly jumped into many unrelated species of higher plants (Palmer 1998).
Additionally, numerous cases of cross-pollination with trangenic crops have been reported in the past year, most notably in the United Kingdom, where a test plot of genetically altered oil seed rape was destroyed after it had been shown to have pollinated nearby plants. A British newspaper quoted the trial manager of Perryfield Holdings, the corporation responsible for the plot, as saying "We expect to be prosecuted."
Notes
Compeerapap, J. (1997). The Thai debate on biotechnology and regulations. Biology and Development Monitor, 32, 13-15.
Hawkes, N. (1997). London Times. October 22.
Hilbeck, A., Baunigartner, M., Fried, P.M. & Bigler, F. (1998). Effects of transgenic Bacillus thuringiensis corn-fed prey on mortality and development time of immature Chysoperla carnea (Neuroptera: Chrysopidae). Environmental Entomology, 27(2), 480-487.
Palmer, J. D. Evolution Explosive invasion of plant mitochondria by a group I intron. PNAS 95(24): 14244-14249.