North America’s monarch butterfly, whose striking appearance and extraordinary migration have made it one of the continent’s most popular insects, has been listed as vulnerable by the International Union for Conservation of Nature, the world’s most comprehensive scientific authority on the status of species.
The decision comes after decades of declining populations, driven by losses in the plants they need as caterpillars and in the forests where adults winter, combined with climate change, the assessment said. To make their decision, the authors viewed around 100 studies, interviewed experts and used criteria from the group’s Red List of Threatened Species.
“It was so sad to see their numbers drop so much, so anything that might help them makes me happy, and I think that label might help them,” said Karen Oberhauser, a conservation biologist at the University of Wisconsin. who has studied monarchs for more than 35 years and has contributed to the assessment. “While it is sad that they need this help, they have reached the point where that designation is warranted.”
The number of western monarchs living west of the Rocky Mountains plummeted an estimated 99.9 percent between the 1980s and 2021. While she’s recovered somewhat this year, they remain in grave danger. Eastern monarchs, which make up most of the population in North America, declined 84 percent from 1996 to 2014. The new designation “Vulnerable” includes both population groups.
In 2020, US wildlife officials determined that monarchs were critically endangered, but declined to include them on the endangered species list, saying conservation of 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, the females lay eggs on milkweed plants from Texas to Canada in a multigenerational journey.
Habitat destruction in these Mexican forests was an early threat, said Anna Walker, an entomologist at the New Mexico BioPark Society who led the assessment. The Mexican government stepped in, creating a reserve in 1986 and expanding it in 2000. While concerns about illegal logging and disease remain, this conservation work, she said, has helped stem the loss of wintering habitat quite effectively.
But a new problem arose, the review noted: American farmers were turning to genetically engineered crops to resist glyphosate, a herbicide used in the weed killer Roundup.
“Glyphosate was suddenly sprayed over a huge farm in the Midwest,” Ms Walker said. “This has destroyed many of the spurge plants that the monarch’s caterpillars rely on.”
Then there is climate change, which exacerbates storms, droughts and other such events that can be catastrophic for already vulnerable populations. The hot, dry springtime in the south is a particular concern for monarch experts. Added to this are broader questions about climate change disrupting old cycles, such as when plants sprout.
“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 number of summer monarchs had decreased in some areas while increasing in others, perhaps in part because warmer weather in the northern areas actually helped monarchs thrive in those regions . But even these authors cautioned that any silver lining could be short-lived, warning that “accelerating climate change may pose growing threats.”
The Red List decision limits the endangered listing to migratory monarchs, which applies to those in North America. It came from the group’s first evaluation 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 North American monarchs is considered one of nature’s wonders: Tiny insects fly thousands of miles north in a few generations and back in just one generation, with individual butterflies flying perhaps more than 2,500 miles.
Monarch experts are eager to enlist the public’s help to save the species. Her message: Plant spurge native to your area, which probably means avoiding tropical spurge (they can do more harm than good, especially in the south). Swamp Milkweed is an attractive, easy-to-grow strain native to all but the westernmost areas of the contiguous United States. This is for egg laying and caterpillars. The butterflies need nectar, so plant native flowers that will bloom when monarchs are around.
dr Oberhauser attributes such interventions to a contribution to the stabilization of population figures in recent years.
“We’re sticking with a number that’s not entirely sustainable,” she said. “But if we didn’t have all of this effort from a lot of different organizations and individuals, I think the numbers would be even lower.”
The latest update to the IUCN Red List also brought bad news for sturgeon: All surviving species are now threatened with extinction, up from 85 percent of the species in 2009. The Yangtze sturgeon, a fish native to China, has been from ” critically endangered” to “extinct”. wild.
Tiger counts, on the other hand, showed a 40 percent increase since the last assessment, which the organization attributes to an improved count combined with stabilized or increasing numbers.
Emily Anthes contributed reporting.