In a statement on Monday, the Mexican Ministry of Economy said its decree was aimed at ensuring that tortillas are made with native Mexican corn varieties, in an effort to ensure the biodiversity of the corn that is grown in the country. It said it would draw on data and evidence to demonstrate that the ban had not had an impact on commerce, and was consistent with the trade agreement.
In the United States, the vast majority of corn planted has been bioengineered to be resistant to herbicides and insects. Bt corn, for example, contains a gene from a soil bacterium that kills the European corn borer, an insect that feeds on maize and other grasses.
Corn can also be modified to be resistant to glyphosate, the most widely used herbicide in agriculture and lawn maintenance in the United States. Glyphosate-based products like Roundup are sprayed on fields, killing weeds and leaving the resistant crops intact.
While the Environmental Protection Agency has said the herbicides pose no risk to human health, overuse can wreak ecological havoc in areas where natural plant species are not resistant to the chemical compound. Environmental groups have warned that glyphosate can be particularly deadly for pollinators like bees and butterflies.
It is illegal to grow genetically modified corn in Mexico, where maize was first domesticated 8,700 years ago and where white corn is a staple crop. Supporters of Mexico’s ban worry that any imports of bioengineered corn would threaten native species, as the varieties can cross-pollinate.
The Mexican government in February moved to soften its restrictions, saying it would allow genetically modified corn to be brought into the country for animal feed and industrial use, though not for human consumption. Tom Vilsack, the U.S. agriculture secretary, said he was “disappointed” in the decision.
It also remains to be seen whether domestic corn production in Mexico is sufficient to replace imports, the eventual goal of the Mexican government. Last year, farmers in Mexico grew 27.3 million metric tons, about 38 percent below domestic demand. One analysis projected that, should the ban remain in place, corn costs could rise by 20 percent in Mexico and increase rates of food insecurity.