Specifically, they are relying on a study about how genetically modified corn kills the butterfly. It's yet another example of junk science marching on. A study at Cornell University found that 11 Monarch butterflies died after eating pollen from a genetically modified corn plant. The plant was engineered to produce a naturally occurring pesticide that kills insects. So, the plant worked.
Butterflies are, after all, insects.
This set off from a blast from the Greenpeace folks saying that we should ban genetically modified corn to protect the butterflies. However, the Monarch butterfly caterpillars in the wild don't eat corn plants, and wouldn't eat the pollen. They had to be force-fed the substance. Junk science, or the misuse of legitimate studies to make a political or economic point, is widespread these days. One study by David Pimentel of Cornell University said the world lost nearly one-third of its topsoil in the last 40 years due to farming and other human activities.