Their habitat beset by logging in Mexico and their numbers by milkweed eradication and pesticide mortality in the U.S., the monarch butterfly has decreased in population so much that the U.S. Fish and Wildlife Service (USFWS) is considering its inclusion on the list of endangered species.
The USFWS announced on December 29 that the monarch population has plummeted by up to 90 percent over the past two decades, mainly because of the destruction of milkweed that is key to their reproduction cycle. That was the same day that three conservation groups and a world-renowned monarch specialist filed a petition requesting the study, which Reuters says will take a year. The Center for Biological Diversity, the Center for Food Safety and the Xerces Society for Invertebrate Conservation, as well as Dr. Lincoln Brower, who has published dozens of articles on the subject.
“Our petition is a scientific and legal blueprint for creating the protection that the monarch so direly needs, and we are gratified that the agency has now taken this vital first step in a timely fashion,” said George Kimbrell, senior attorney for the Center for Food Safety, in a statement noting that genetically engineered crops that are immune to milkweed pesticides are partly to blame for the monarch’s decline. “We will continue to do everything we can to ensure monarchs are protected.”
The insects migrate annually for more than 3,000 miles between Canada and forested mountainsides in Mexico, where they winter from November through March. The butterflies reproduce along the way, mostly in the Midwest. If they cannot lay eggs that hatch and keep on flying, then the species could have trouble surviving, the Xerces Society said.
On New Year’s Eve the USFWS initiated a 60-day public information period to seek information on the butterfly species’ biology, range and population trends, habitat requirements, genetics and taxonomy; its current range and distribution patterns; population levels past, present and projected future; any so-far-undocumented information about the monarch’s life cycle. The USFWS also wants details on the insects’ temperature tolerance and climate requirements, and on what conservation measures are already in place. This will help the federal agency evaluate the various criteria for inclusion on the list. The deadline for receiving information is March 2.
Besides the habitat destruction, the monarchs can fall prey to predators, which means they must have resilient numbers, the Xerces Society said.
“Monarchs need a very large population size to be resilient to threats from severe weather events and predation,” the society said in its statement. “Nearly half of the overwintering population in Mexico can be eaten by bird and mammal predators in any single winter; a single winter storm in 2002 killed an estimated 500 million monarchs—14 times the size of the entire current population.”