In April 2002, I sat in the office of UC Berkeley environmental science professor Ignacio Chapela
as an ancient telephone chortled incessantly with calls from scientists and journalists curious about his latest study, a paper published in Nature
showing how genes from GM corn entered local varieties of the plant in Mexico, where GM crops are banned. Samples of the corn sat in vials on his desk. An international controversy had erupted over the experiment, and earlier that month the prestigious journal published an unprecedented near-retraction. “Nature
has concluded that the evidence available is not sufficient to justify the publication of the original paper,” said a terse editorial note. Chapela admitted to making a few interpretative mistakes, but stood by his findings even when a study by a different team of researchers in 2005 was unable to replicate his results. His findings were finally corroborated
this week by scientists from Mexico, the United States, and the Netherlands who looked at thousands of seed samples from hundreds of Mexican corn fields and found that around 1 percent of them had genes that had jumped from GM varieties. Even before this week, major detractors agreed with Chapela's main point. Corn disperses pollen easily, so one should expect that GM pollen carried by the wind has mated with local corn varieties in much of the world.
Although neither expensive--total cost $2000--nor surprising, Chapela’s study was attacked because it provoked ongoing feuds. Disagreements about what might happen when GM crops interbreed with their unaltered neighbors are now more than a decade old. Scientists still debate whether transgenics will diminish genetic diversity in local crop varieties, kill beneficial creatures, or reduce the ability of entire plant populations to survive.
Scientists already know that pollen from GM crops can kill beneficial insects. For example, the Bt gene in corn poisons pests like the European corn borer but could also inadvertently wipe out the valuable Typhlodromalus aripo. The T. aripo, as it is known, eats both corn pollen and the ignominious green mite, which wreaked havoc on Africa’s cassava crop in the 1980s and early 90s. The mite was accidentally introduced from South America and scientists combated it in 1993 by importing the T. aripo from Brazil. After it went to work eating mites, it immediately increased cassava yields by 35%. The addition of Bt pollen to that diet could be a boon to the mites and a disaster for T. aripo and farmers. “If it destabilized cassava,” says Andrew Paul Gutierrez, a Berkeley researcher who has done computer modeling on GM crops, “it could destroy the basic food staple for 220 million Africans in an area twice the size of the United States.”
Accepting such risks becomes even more difficult given that Bt is probably only a temporary solution to insect invasions. Last February, University of Arizona researcher Bruce Tabashnik documented the first case, in GM cotton, of insects developing a resistance
to the Bt gene. “My own experience in the history of insect resistance is that they develop resistance to whatever control measure is used against them,” he told me in 2002. “I think it’s just a matter of time.”