Monarch butterflies, known for their astounding multi-thousand-mile migrations, have officially made their way onto the International Union for Conservation of Nature’s (IUCN) Red List. The striking orange and black insects are listed as Endangered, as of July 21.
The listing follows decades of steep declines in monarch numbers. The once massive eastern monarch population, which spends winters in Mexico, has plummeted an estimated 80% over the past twenty years. The smaller western population, which migrates to coastal California in the cooler months, has been faring even worse. The butterflies lost more 99% of their numbers between the 1980s and 2021. From 2018 to 2019 alone, western monarchs declined by 86%. In 2021 western monarch counts were so low, down to fewer than 2,000 from what was once a population estimated above 10 million, that there were whispers of imminent extinction.
“It is difficult to watch monarch butterflies and their extraordinary migration teeter on the edge of collapse,” said IUCN entomologist, Anna Walker, in a press statement. “But there are signs of hope,” she added.
In the past year, there has been renewed faith in the species’ ability to rebound as both eastern and western butterfly surveys showed unexpected population upticks. At the monarch overwintering site in Mexico, an annual survey of their extent found they were occupying 35% more space than the year before, according to the World Wildlife Foundation. The butterflies were clustered in trees across 7.02 acres of forest, up from 5.19 acres the year before. (For context: in the mid 90's, the monarchs covered 45 acres.)
And at the coastal California overwintering sites in 2022, butterfly counts were up to about 250,000— more than a hundred-fold increase from the year before, according to the non-profit invertebrate conservation group, Xerces Society.
These most recent numbers alone are not evidence that the butterflies’ problems are solved. Insect populations often undergo rapid fluctuations because of how quickly they can multiply given the right conditions. Instead, the single-year butterfly boom demonstrates the species’ resilience and the potential for recovery.
Monarchs still face myriad challenges. Their breeding habitat across the U.S. and Canada has shrunk between 22% and 72% in the past ten years, according to the IUCN. Plus, deforestation in both Mexico and California has drastically reduced their overwintering grounds as well. (Note: planting native milkweeds and other native nectar plants in your area is a great way to help combat this habitat decline).
Then, there’s agricultural pesticides. One 2020 study in California found residues from 25 different chemical insecticides on the milkweed plants monarchs rely on, even miles away from farms. Every single plant sampled had at least some pesticide on it. One third of all milkweed sampled carried a level of pesticide high enough to kill half of all the monarchs who might feed on it.
Climate change carries big risks for monarchs as well. The insects’ overwintering habits, migration pathways, and breeding success are all dependent on timing. The butterflies need nectar sources to flower and milkweed leaves to emerge on cue for the choreography to work.
So, even amid the recent numbers uptick, many butterfly scientists believe the new Endangered classification is needed. “Although it’s sad that they need that help, that they’ve reached the point where this designation is warranted,” said entomologist Karen Oberhauser to the New York Times.
And though it can feel like a death knell, placement on the IUCN Red List is actually more like sounding an alarm. It draws attention, signals urgency, and could get monarch butterflies more of the resources and support that the species needs. There are lots of groups, like the Xerces Society, working to save monarchs. With the Endangered designation, the necessity of that work and the butterflies’ plight is clearer than ever before.