Report blames Monsanto for decline of monarch butterflies

Feb 12, 2015

Credit Derek Ramsey/Wikimedia

A new report from the environmental group The Center for Food Safety says a Monsanto herbicide is to blame for a vast decline in the monarch butterfly population.

The Glyphosate herbicide, commonly known as Roundup, destroys weeds, including the common milkweed. And that’s a problem for monarch butterfly caterpillars, which only eat the plant.

As milkweed has disappeared from Midwest farms, there’s been a steady decline in the number of monarchs overwintering in Mexico.

Iowa State University researcher John Pleasants says billions of milkweeds have been lost in the Midwest since about 1999, which amounts to over 60 percent of the milkweeds present at that point in time. “That’s pretty close to a smoking gun,” he said.

Monarch numbers have dropped by 90 percent. A Monsanto representative did not respond to the report.