A case vs GM crops

More than 578 scientists from all over the world have signed an open letter urging President Arroyo to declare a moratorium on the release of genetically modified (GM) crops for reasons of safety and other concerns.

The call is being supported by the Ecological Society of the Philippines and the International Union for Conservation of Nature and Natural Resources (IUCN).

Many independent scientists along with the British Medical As-sociation now believe there is suf-ficient evidence to indicate that GM crops pose serious risks to health and environment. A num-ber of the most prominent scien-tists have formed an Independent Science Panel on GM which is due to present scientific evidence to the public while calling for a ban on GM crops and endorsing organic sustainable agriculture.

The group is urging President Arroyo to reconsider the govern-ment’s go-signal for the commer-cial propagation of Monsanto’s Bt corn which is a harmful GM crop in many ways, as summarized in a recent report produced by the Institute of Science in Society in London, UK which is headed by Dr. Mae-Wan Ho.

Bt crops are genetically engi-neered to produce insecticidal pro-teins derived from genes of the bacterium Bacillus thuringiensis (Bt). While Bt is a natural insec-ticide used safely and occasionally as a spray by conventional organic farmers, genetically engineering Bt genes into plants so that the toxins are expressed in relatively high levels in a large proportion of the plants throughout most of their growing period is another matter. Abundant evidence of harmful effects on the environment has already emerged.

Bt crops impact negatively on non-target endangered species such as the monarch butterfly, the black swallowtail and other lepidopteran species. Beneficial species such as lacewings that prey on cornborer were also harmed when fed on an artificial diet containing Bt toxin or on corn borers or other lepidopteran larvae that had fed on Bt corn.

Research conducted in China show that while Bt cotton is effec-tive in controlling the primary pest cotton when first planted, there are adverse impacts on parasitic natural enemies. Furthermore, populations of secondary pests in-creased in Bt cotton fields after the target (bollworm) had been con-trolled, some of which then re-placed bollworm as primary pests and damaged cotton growth.

Bt toxin is released in root exu-dates from Bt corn. It accumulates and persists in soil and retains insecticidal, immunological and other biological activities, with potentially large impacts on soil ecology and fertility.

The efficacy of Bt crops in pest control is compromised when pests evolve resistance to Bt toxins. Such resistance has already become a big problem in the United States and management strategies have had to be introduced several years ago, based on planting "refugia" of non-Bt crops and developing Bt crops that express high doses of the toxin. Recent research indicates that resistant strains are even able to obtain additional nutritional value from the toxin, thus making them even more serious pests than before.

Bt genes could spread from Bt crops to create weeds. Hybrids of cultivated Bt sunflowers and wild sunflowers were found to have 50 percent more seeds than control hybrids without the Bt genes, and were physically fitter, when deprived of water and nutrients. Crosses between GM canola containing the Bt gene and related weed, birdseed rape, produced hybrids that are just as toxic. The transfer of Bt genes, conferring insect resistance, could give the hybrids an edge in the wild, with the potential of creating superweeds.

Evidence is also accumulating that many of the Bt toxins are harmful to health. While Bt toxins are stored as inactive crystals (Cry) in the bacterial spores and must be activated in the insect gut, Bt toxins in GM plants are usually of the activated form. Due to different gut, Bt toxins in GM plansts are usually of the activated form. Dut to different gut pH and digestion of the protoxin, humans are not exposed to the activated form of the toxin in Bt crops.

Bt toxins may be actual and potential allergens for human beings. Some field workers are exposed to Bt spray experienced allergic skin sensitization and induction of lgE and lgG anti-bodies to the spray. A team of scientists have cautioned against releasing Cry-containing plants and plant products for human use. These scientists demonstra-ted that recombinant Cry1Ac protoxin from Bt is a potent sys-temic and mucosal immunogen, as potent as cholera toxin.

A Bt strain that caused severe human necrosis (tissue death) killed mice within eight hours from clinical toxic-shock syndrome. Both Bt protein and Bt potato harmed mice in feeding experiments, damaging their ileum (part of the small intestine). Both the groups of mice fed Bt potatoes of potatoes piked with Bt toxin revealed common features such as the abnormal appearance of mitochondria, with signs of degeneration and disrupted short microvilli (microscopic projections on the cell surface) at the surface lining gut.

Because Bt and Bacillus anthracis (anthrax species used in biological weapons) are closely related to each other and to a third bacterium, Bacillus cereus, a common soil bacterium and cause of food poisoning, they readilly exchange plasmids (circular DNA molecules containing genetic origins of replication that allow replication independent of chromosome) carrying toxin genes. If B anthracis picked up Bt genes from Bt crops, new strains of B anthracis with unpredictable properties could arise.

Finally, there is no evidence that Bt corn reduces insecticide use, or that it yields economic advantage to farmers. A farm-level economic analysis of Bt corn demonstrated less net profit, lower corn prices and lost corn exports. According to this analy-sis, from 1996-2001, American farmers paid at least $659 million in price premiums to plant Bt corn, while boosting their har-vest by only 276 million bushels worth $567 million in economic gain.

In the light of all available evi-dence against GM crops in gene-ral and Bt corn in particular, the group is urging President Arroyo to ban the commercial release of Bt corn in the Philippines.