The North American monarch butterfly, whose showy appearance and extraordinary migration have made it one of the continent’s most beloved insects, is classified as endangered by the International Union for Conservation of Nature, the world’s most comprehensive scientific authority on the subject. of the status of species.
The decision comes after decades of declining populations due to losses in the plants they need as caterpillars and in the forests where adults spend the winter, coupled with climate change, the review finds. The authors reviewed about 100 studies, interviewed experts, and applied criteria from the group’s Red List of Threatened Species to arrive at their decision.
“It was so sad to see their numbers go down like that, so anything that could help them makes me happy, and I think this designation could help them,” said Karen Oberhauser, a conservation biologist at the University of Wisconsin who is a researcher at the University of Wisconsin. Monarchs has studied for over 35 years and contributed to the assessment. “While it’s sad that they need that help, they’ve reached the point where this designation is warranted.”
The number of Western monarchs living west of the Rocky Mountains fell by an estimated 99.9 percent between the 1980s and 2021. Although they recovered somewhat this year, they remain in grave danger. Eastern monarchs, who make up the bulk of the population in North America, fell by 84 percent between 1996 and 2014. The new endangered species designation covers both populations.
In 2020, U.S. wildlife officials found that monarchs were in danger of extinction, but refused to add them to the endangered species list because they said preserving other species was a priority.
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Monarch caterpillars depend on milkweed, the only plants they can eat. After leaving their wintering grounds, which for most monarchs are concentrated in just a few acres of forest in central Mexico, females lay eggs on milkweed plants from Texas as far north as Canada on a multi-generational journey.
Habitat destruction in those Mexican forests was an early threat, said Anna Walker, an entomologist with the New Mexico BioPark Society who led the assessment. The Mexican government intervened, creating a reserve in 1986 and expanding it in 2000. While concerns about illegal logging and disease remain, that conservation, she said, has curbed the loss of wintering habitat quite effectively.
But a new problem arose, the review said: U.S. farmers turned to crops genetically modified to resist glyphosate, a herbicide used in the weed killer Roundup.
“Glyphosate was suddenly sprayed over a large agricultural area in the Midwest,” said Ms. Walker. “That took a lot of the milkweed plants that the monarch caterpillars rely on.”
Then there’s climate change, which exacerbates storms, droughts and other such events that could be catastrophic for already vulnerable populations. The hot, dry spring seasons in the south are of particular interest to monarch experts. Add to this broader questions about climate change disrupting ancient cycles, such as when plants germinate.
“We’re starting to see this kind of mismatch between when insects are ready to start spring and when plants are ready,” Ms Walker said. “There are a lot of unknowns.”
A recent study complicated the picture, finding that the summer abundance of monarchs had decreased in some areas and increased in others, perhaps in part because warmer weather in the northern areas helped monarchs thrive in those regions. But even those authors indicated that a silver lining could be short-lived and warned that “accelerating climate change could bring growing threats.”
The Red List decision limits the endangered list to migrating monarchs, which applies to those in North America. It came from the group’s first assessment of these butterflies. The broader species includes a non-migratory variety in the Caribbean and from southern Mexico to northern South America.
The migration of the North American monarchs is considered one of the wonders of the natural world: tiny insects fly thousands of miles north over the course of a few generations and back in just one generation, with some butterflies perhaps exceeding 2,500. flying miles.
Monarch experts are eager to enlist the public’s help in saving the species. Their message: plant milkweed that is native to your area, which probably means: avoid tropical milkweed (it can do more harm than good, especially in the South). Swamp milkweed is an attractive, easy-to-grow variety that is native to all but the westernmost regions of the contiguous United States. That’s for the egg-laying and caterpillars. The butterflies need nectar, so plant native flowers that bloom when frosts are in your area.
dr. Oberhauser attributes such interventions to helping to stabilize population numbers in recent years.
“We’re holding onto some that aren’t quite sustainable,” she said. “But if we didn’t have all this effort from many different organizations and individuals, I think the number would be even lower.”
The latest update to the IUCN Red List also contained bad news for sturgeon: All surviving species are now in danger of extinction, compared to 85 percent of species in 2009. The Yangtze sturgeon, a fish from China, is critically endangered. to extinct in the wild.
Tiger numbers, on the other hand, showed a 40 percent increase since the previous assessment, which the organization attributes to better counting coupled with stabilized or increasing numbers.
Emily Anthes reporting contributed.