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They are an astonishing and intrepid species in North America. But in some places, populations of the migratory monarch butterfly, an iconic subspecies of the monarch, has dwindled over the past few decades.

Recently, the International Union of Conservation of Nature (IUCN), a conservation organization, put the traveling species on its infamous Red List, a grim catalog of species the group concludes are threatened or endangered. The IUCN says the migratory monarchs, whose populations in their winter breeding grounds have plummeted by between 22 and 72 percent, are endangered with extinction.

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While this red-listing by an international organization might convey a sense of urgency to immediately protect monarch butterflies, it doesn't give legal protections to monarchs in the U.S. But many ecologists warn it’s high time for monarchs to be actively guarded from extinction, given the diverse threats these spectacular insects face. 

It's hard for people to wrap their heads around the idea that an animal they see frequently in the summers is in trouble, said Emma Pelton, a biologist who was part of the recent IUCN monarch assessment. 

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An amazing species

The iconic species is remarkable for many reasons. Monarchs are very good pollinators. Like bees, when monarchs sip nectar from flowers, pollen dust sticks to their bodies, allowing them to carry pollen and fertilize other plants.

Monarchs are the only known butterfly speciesthat complete a two-way migration, like birds. Every fall, millions of monarchs travel up to an astonishing 3,000 miles from their summer breeding grounds in North America to spend winter in the forests of Mexico (a phase called "overwintering"). Mexico's mountain climate is ideal for monarchs to slow down their metabolism, conserve energy, and avoid freezing. 

But overwintering also exposes monarchs to vulnerabilities, said John Pleasants, an associate professor of ecology at Iowa State University. 

Excessive herbicide use eradicates milkweeds, which monarchs depend on for laying eggs as they migrate large distances. Credit: Raquel Lonas / Getty Images

The monarch's decline

Since the mid-1990s there have been three major monarch mortality events in the overwintering grounds, explained Pleasants. "These are big winter storms that come in, and the butterflies get all wet, cold, and they die," he said. Even leaving Mexico and moving north towards Texas exposes them to winter vulnerabilities too, owing to drought. "If it's too dry, if it's too hot, you're not going to get off to a good start," he said. 

In addition to these natural environmental hardships, human activities like deforestation and habitat depletion eradicate milkweed plants, which monarchs solely rely on for laying eggs as they migrate. Excess pesticide use is blamed for milkweed loss, too, said Pleasants. 

"It’s really heartbreaking that these monarchs have to be classified as endangered by the IUCN."

Monarch populations declined heavily between the late 1990s and 2007. Pleasant’s research found that the decline was linked to the use of the popular Roundup Ready herbicide, which is widely sprayed before and after sowing crops to control weeds. Corn and soybeans were not affected by the herbicide, Pleasants said, but all the other plants in the fields were killed, including milkweeds. 

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The adverse impacts of herbicides, habitat depletion, and natural mass mortality events add up. That's why monarchs deserve to be listed as endangered, Pleasant said.

"It’s really heartbreaking that these monarchs have to be classified as endangered by the IUCN," said Stephanie Kurose, an endangered species policy specialist at the Center for Biological Diversity in Arizona. There’s an 80 percent chance that migrating monarchs will go extinct in the next 50 years, cautions Kurose.

She also acknowledged that the IUCN red listing does not offer any legal protection to monarchs in the U.S. 

Monarchs aren't protected...yet

The IUCN is an international body of scientists that analyzes the threats a species encounters, and, if necessary, puts them on its list of threatened or endangered species. Over 41,000 animal and plant species are listed as endangered, which the conservation group updates several times a year. That said, a Red List status granted by the IUCN doesn’t create legal protections for endangered species in the U.S. 

Rather, the U.S. Fish and Wildlife Service is the agency that establishes legal protections for species and works with the scientific community to recover endangered animals and plants to stable population levels. In 1973, Congress passed the powerful Endangered Species Act, allowing the Fish and Wildlife Service to protect and recover dwindling species, like the Bald Eagle. Critically, the agency allocates funds for protecting endangered species. (Yet, importantly, researchers have found that a vast majority of endangered species are underfunded, which makes the recovery of many imperiled animals challenging.)

"We really need the Biden administration to immediately protect monarch butterflies under the Endangered Species Act"

The Fish and Wildlife Service has yet to list migratory monarchs as endangered. In 2020, the agency concludedthat "listing the monarch butterfly as an endangered or threatened species is warranted," considering the threats they face, but that there is a huge backlog of other plant and animal species that need to be prioritized for conservation. 

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"We really need the Biden administration to immediately protect monarch butterflies under the Endangered Species Act," the Center for Biological Diversity’s Kurose told Mashable. Kurose noted that the agency might make a decision about protecting monarchs sometime in 2024. Pelton, who also leads the monarch conservation program at the Xerces Society, a conservation group, said their organization was one of the original petitioners to have the monarch reviewed, and hopefully listed by the Fish and Wildlife Service. "We’ve been in that camp for many years," she said. 

What's more, raising awareness about a popular flagship species like monarchs can stoke the public to become interested in conserving not just monarchs, but also other wild animals, Pelton told Mashable. 

A cluster of overwintering monarch butterflies. Credit: Maureen P Sullivan / Getty Images

Not all experts, however, are convinced with the IUCN’s decision to list the iconic butterfly species as endangered. Andy Davis, an animal ecologist at the University of Georgia, questions the timing of this decision, as some monarch populations have been thriving reasonably well in the past couple of years in NorthAmerica. "This decision is based on a misunderstanding of the biology of the monarchs, and perhaps a misunderstanding of the science," Davis told Mashable. 

Davis’ recent studyanalyzed the trends in monarch populations in their breeding range during summer. The IUCN’s analysis, though, is based on the wintering colony size, explained Davis. It might be easy to count the monarchs when they are overwintering, he said, as they don’t move that much. But counting the number of butterflies when they make a return during spring, as Davis’ study did, gives the real picture of their population numbers, because that's when they breed, said Davis. "There's no evidence that the breeding range is shrinking," Davis argues.

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Ecologists like Orley R. Taylor, Jr., who directs Monarch Watch, an organization that tracks monarch migration, agrees that the overall monarch population has not declined for the last 10 to 15 years, and that their numbers remained almost stable. That said, Taylor says there is some justification for putting monarchs on the IUCN endangered list, given the unpredictable long-term threats from climate change. Monarchs were hit with multiple mass deaths over the past few decades, thanks to changes in weather patterns and torrential rain, he said. "We have been lucky so far, because the population has been really robust," Taylor told Mashable. 

Iowa State University’s Pleasants agrees with Taylor’s views. Even if 75 percent of monarchs die, tens of millions will still be left. But when the population decreases, then the chances of it becoming too small, and vulnerable, come into play. Already, in 2013, the overwintering monarch population in Mexicowas down to 2.67 hectares, a size little bigger than a football field, Pleasants explained. 

Taken together, the IUCN’s decisionstresses the need to take precautionary steps to protect monarchs, even if there is some scientific uncertainty about their future, Taylor said. "Because if you don't know what's going on, do something that you know is the safest thing you can do. And so that's what I think the IUCN thing is all about," he told Mashable.