The genetically modified (GM) debate intensified in May 1999, when the journal Nature published a Cornell University study showing that monarch butterflies died or developed abnormally after contact with milkweed dusted with the pollen of genetically engineered "Bt-corn". The Bt-corn includes a gene from a bacterium that kills the European corn borer, a major insect pest. A complication neither industry or government had foreseen, dead monarch butterflies became a vivid, emotional symbol of the potential dangers of GM crops.

Despite the negative publicity, U.S. officials continued to defend the technology. In July 1999, Agriculture Secretary Dan Glickman told the National Press Club that the higher yields and pest resistance of biotech crops had "an enormous potential to combat hunger." Nonetheless, he ordered an independent review of the U.S. Department of Agriculture's (USDA) approval process for GM crops. At the time, about 50 genetically altered plant varieties had been approved, and not a single application for a GM crop had never been turned down. During hearings on biotechnology in October 1999, U.S. Senate Agriculture Committee Chairman Richard Lugar praised genetic engineering, likening it to the work of Galileo.

Also in 1999, angry French farmers dumped cattle manure in the parking lots of McDonald restaurants to protests the American company's GM food ingredients.

In September 1999, food-ingredient powerhouse Archer Daniels Midland, based in Decatur, Ill., cited consumer preference as its reason for asking suppliers to segregate non-GM crops to preserve their identity. Soon after, Monsanto bowed to public pressure when the company announced it would abandon development of its "terminator" seeds, genetically engineered to produce infertile offspring.

In January of 2000, environmental ministers from 50 nations signed a treaty acknowledging the right of governments to ban GM crop imports. A month later, members of the activist group Greenpeace were arrested off the coast of Wales after boarding a ship laden with 60,000 tons (60,960 metric tons) of genetically modified soybeans bound for a British mill. The protest was designed to call attention to a meeting in Edinburgh, Scotland, of 400 food-science experts convened by the Organization for Economic Cooperation and Development to debate the health questions surrounding GM foods.

Also in February, experts reviewed the pros and cons of GM foods at a symposium sponsored by the USDA during the annual meeting of the American Association for the Advancement of Science in Washington, D.C. Several speakers said that crops engineered for increased yields and better nutrition -- such as a new, transgenic rice loaded with vitamin A -- could be instrumental in relieving world hunger.

The GM industry suffered a setback in March, when the USDA ordered that any food containing GM ingredients cannot be labeled "organic". The decision could further hamper the ability of U.S. farmers to market GM food within the European Union, where organic product are popular and resistance to GM products runs high.