The iconic migratory monarch butterfly has had a rough past couple decades. While its numbers can vary year to year, populations east and west of the Rockies have seen an overall long-term decline—to the point where conservation biologists and butterfly lovers are concerned for its survival as a species. Yet despite its dwindling health, the monarch has not been placed under federal protections in the US.

A global leading authority on endangered species conservation disagrees, however. After conducting a two-year assessment, last month the International Union for Conservation of Nature (IUCN) designated the monarch butterfly as endangered on the organization’s Red List of Threatened Species. 

“This is an assessment by an international scientific body that looked at all of the data and said monarchs are endangered,” says Karen Oberhauser, an expert on monarch butterfly biology and conservation and the director of the University of Wisconsin-Madison Arboretum. “That means they’re in danger of their population going so low that it wouldn’t be able to recover.” 

In other words, monarch butterflies could be at risk of extinction. The destruction of precious milkweed habitat as well as climate change are the primary threats to their survival, researchers report, with the IUCN stating that numbers have sunk between 22 to 72 percent over the last decade. The boldly striped insect lays its eggs and feeds on milkweed in breeding grounds in Canada and the US. After journeying up to 3,000 miles, the Western monarch subspecies overwinters on the California coast, while the Eastern one migrates down to Mexico. The “bellwether” for monarch populations, Oberhauser says, is how many butterflies make it to the overwintering grounds each year.

Oberhauser and the IUCN scientists hope that the designation will prompt the public, and even policymakers, to see the urgency of the state of monarchs. However, moving a species onto the IUCN Red List does not initiate federal protective measurements. “This is purely a scientific designation,” says Oberhauser, who helped draft the IUCN assessment. “It doesn’t have any legal requirements.”

The unique migratory lifestyle of monarchs presents a tricky conservation conundrum. Canada, Mexico, and the US each have separate wildlife agencies and processes that determine whether a species should be federally protected. While certain areas and states like California have monarch-specific legislation, protection is “piecemeal” and imperfect, says Oberhauser. Mexico does federally protect the butterflies and the bioreserve where they overwinter. In Canada, the Committee on the Status of Endangered Wildlife has deemed the species endangered, but still does not protect it under the Species at Risk Act. Similarly, the US Fish and Wildlife Service (USFWS), which establishes recovery efforts and reviews candidate plants and animals under the Endangered Species Act, has not listed the monarch as endangered. 

While the IUCN Red List is scientifically reviewed, it is separate from threatened and endangered species lists regulated by individual countries. This might cause some confusion among the public, says Delbert André Green II, who studies the genetics and evolution of migrating monarchs at the University of Michigan.  

“It might even cause a bit of a panic in that, now, people might think that it’s a listing of ‘endangered’ under the Endangered Species Act, which is not true,” says Green. “The IUCN recognizes many more species as endangered compared to the Endangered Species Act, so monarchs are not the only one that are in this situation.”

Currently, more than 1,300 species are listed as endangered or threatened in the US, compared to the more than 147,500 species on the IUCN Red List. The USFWS has been made aware of the IUCN’s decision, an agency spokesperson told Popular Science in an email, further stating that “this action does not constitute a US Fish and Wildlife Service Endangered Species Act (ESA) listing decision.”

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