FALLS CHURCH, Va. — Monarch butterfly populations have declined by 90 percent from the average over 20 years. The U.S. Fish and Wildlife Service (FWS) is reviewing the status of monarchs to determine if the familiar orange-and-black pollinator should be listed as threatened under the Endangered Species Act (ESA).

“The Xerces Society for Invertebrate Conservation has been working on monarch butterflies and their conservation for decades,” said Sarina Jepson, Xerces director of the endangered species program. “In the last couple of years we have become very concerned about the status of this familiar, widespread butterfly because it is becoming so much less common.”

“The Xerces Society, the Center for Food Safety, the Center for Biological Diversity and Dr. Lincoln Brower, who is probably the world’s expert on monarchs, were the authors of the petition to the FWS to consider the status of the monarch butterfly.”

Monarch populations are estimated every year by measuring the area they occupy where they overwinter in Mexico, Jepson said. World Wildlife Fund researchers measure that area. They estimate there are approximately 50 million monarchs per hectare. In the mid-1990s there were up to a billion – that was the highest estimated number.

“Recently the research community has realized that the loss of milkweed within the American Midwest is playing a larger role in the monarch decline than impacts from logging in Mexico,” Jepson explained. “Milkweed is the only plant that monarch caterpillars can eat.”

Researchers have documented about a 60 percent decline in milkweed from Midwest areas, and a subsequent loss of the butterflies. They say use of the herbicide glyphosate, which kills milkweed, skyrocketed with the increased planting of genetically modified (GMO) corn and soybeans resistant to glyphosate.

From a number of published research papers it is clear the use of glyphosate herbicides on GMO corn and soybeans in the Midwest is probably the main cause for the decline of monarchs, asserted Doug Gurian-Sherman, senior scientist of sustainable agriculture for the Center for Food Safety.

Also, the data show monarchs even preferred milkweed found in crop fields over milkweed growing in non-cultivated areas, he said. The monarchs were laying their eggs in farm fields at a rate of about 4-to-1 compared to milkweed found in other places.

Many groups, including the Xerces Society, hope with more attention focused on the monarch’s plight, there may be extensive habitat restoration for the butterflies. This restoration could be on private lands and farms through farm bill conservation programs.

Monsanto Co. is talking with experts from universities, nonprofits and government agencies about the restoration of monarch habitat in Crop Reserve Program (CRP) land, on-farm buffer strips, roadsides, utility rights of way and government-owned land, Charla Lord of Monsanto said by email.

“A number of factors are contributing to fewer monarch butterflies migrating from the United States to Mexico,” Lord said. “The declining availability of milkweed plants for butterfly habitat here in North America is certainly a contributing factor. This challenge is complicated, since monarchs need milkweed to survive, but farmers consider the plant a weed that competes with their crops for water, soil and nutrients.”

Saying a species is closing in on extinction when most disagree or calling on government to list monarchs as threatened species under the ESA helps put the monarchs in the news – but it doesn’t do anything to help solve the problem, Lord said. Regardless of how these processes unfold, she said Monsanto is committed to working with others to put more monarchs in flight.