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More Bad News:  Monarch butterflies lose sanctuary in Mexico as climate changes

More Bad News: Monarch butterflies lose sanctuary in Mexico as climate changes

The population of monarch butterflies wintering in Mexico has dropped 22 percent from the previous year, the World Wildlife Fund said on March 21, 2023.

A previous version of this article misstated the nature of the eastern monarch butterfly's population decline in the past 25 years. The population declined but did not do so steadily. The article also mischaracterized biologist Emma Pelton's comments to another media outlet. Pelton was discussing eastern monarch butterflies potentially feeding into the western monarch butterfly population during the breeding season, not eastern monarch butterflies wintering in the West Coast. The article has been corrected.

Every year, millions of monarch butterflies make their way across North America to spend winters in the same forests of central Mexico’s Michoacán state — a phenomenon that remains an evolutionary mystery.

But in just one year, the population of monarch butterflies wintering in those hillsides dropped 22 percent, according to a World Wildlife Fund (WWF) Mexico report released last week.

Monarch butterflies are considered one of the world’s oldest and most resilient species. Their life cycles depend on optimal conditions: temperatures between 55 and the low 70s when they migrate, an abundance of milkweed when they mate, and some rain during the winters.

Climate change is playing havoc with Mexico’s monarch butterfly migration

But climate change has scrambled the consistent weather patterns they rely on, and more butterflies are dying. Monarch butterflies are known as experts of climate adaptation, but it’s becoming much harder for them as global warming and logging hurt habitats where they breed and spend the winter. In 2022, the species was entered into the International Union for Conservation of Nature’s Red List of Threatened Species as “endangered.”

Activists say restoring monarch habitats is critical — as is slowing down global warming. “It’s not just about conserving a species, it’s also about conserving a unique migratory phenomenon in nature,” Jorge Rickards, the general director of WWF Mexico, said in last week’s report. “With 80% of agricultural food production depending on pollinators like monarchs, when people help the species, we are also helping ourselves.”

Monarch butterflies in the oyamel forest at El Rosario sanctuary in Mexico. (Luis Acosta/AFP/Getty Images)

Michoacán’s Monarch Butterfly Biosphere Reserve is a UNESCO World Heritage site and is considered the prime location for the monarchs. They are able to cluster in the dense forests of the nearly 140,000-acre reserve and shelter from winds, rain and low temperatures.

The population of butterflies is calculated by the number of acres they cover when gathered on tree branches. The monarch population fell from 7 acres down to 5.5 acres in one year; they once covered more than 45 acres.

The forest area occupied by monarch butterflies in Mexico has declined over the past 25 years, for reasons including the huge loss of habitat in the biosphere reserve, the WWF report says. Between March 2021 and April 2022, the loss of monarch-friendly forest in the reserve tripled from 46.2 acres to over 145 acres, said Gloria Tavera, conservation director of Mexico’s Commission for National Protected Areas, the Associated Press reported.

More than half the tree loss was due to sanitary logging — the removal of dead or sick trees weakened by lack of water and therefore more vulnerable to pests and diseases, fires or storms, according to another WWF report released last week.

"Extreme temperatures” in the United States have contributed to the decline in the monarch butterfly’s population in Mexico this winter, conservationists said. (Video: Reuters)

While the WWF warns that the presence of eastern monarch butterflies has dropped sharply in Michoacán and the state of Mexico, the population of western monarch butterflies tallied in California and Arizona this year was over 330,000 — the highest number in the past six years.

Emma Pelton, a conservation biologist at the Xerces Society, told CBS it was not clear why the population of western monarch butterflies had rebounded, but one explanation could be that eastern monarch butterflies were mixing with their western counterparts during the breeding season.

“Some of that kind of leakage could be occurring, and I don’t think we fully understand the system enough to say what it is,” she said. “It’s a sign we have a second chance. But I think one thing it’s not is that all is well or that we all made human actions that magically made it all better.”

A monarch butterfly takes off from a tree trunk in the winter nesting grounds of El Rosario sanctuary in Michoacán, Mexico. (Rebecca Blackwell/AP)

Droughts, frost and “extreme temperatures” across the United States are killing the monarchs’ food source — milkweeds — and causing their habitats to dwindle, the director of Mexico’s nature reserves, Humberto Peña, said at a news conference last week.

The effects of climate change are particularly bad on the West Coast, where severe weather has repeatedly battered California. The western monarch population dropped from 10 million butterflies in the 1980s to just 1,914 butterflies in 2021, the IUCN said.

Monarchs lie on snow after a strong winter storm hit the Ocampo community in Michoacán. (Enrique Castro/AFP/Getty Images)

Humans have long helped destroy the monarch butterfly habitats of Michoacán, which has a long history of illegal logging.

It didn’t take long for the drug cartels and illegal loggers to come in and profit off their community. And so in the early 2000s, in an effort to kick them out, residents began reforesting the hillsides. With no help from the police, the farmers took up arms and set off on a long and arduous fight to protect their village and conserve the butterfly habitats.

The Mexican government eventually outlawed logging in the area. But the ban only worsened tensions between local loggers and conservationists. Between 2005 and 2006, 461 hectares of land were lost to illegal logging.

Homero Gómez González, Mexico’s monarch butterfly defender, found dead

Homero Gómez González was a former logger who became a conservationist and was one of central Mexico’s most prominent defenders of the monarch butterfly. In an interview with The Washington Post in December 2019, he said he began working with scientists and conservationists from the WWF to put Michoacán’s Rosario sanctuary on the map and bring in tourism. “We were afraid that if we had to stop logging, it would send us all into poverty,” he said.

A month after talking to The Post, he was found dead, sending shock waves through environmental activist communities across North America. It was quickly suspected that illegal loggers were behind his death.

Flower petals fall as family and friends gather at the grave of anti-logging and monarch butterfly activist Homero Gómez González. (Rebecca Blackwell/AP)

On Jan. 23 this year, Crescencio Morales introduced its first class of state-trained and approved “community guard” forest rangers. Worried about heightened cartel-related violence and a farmers’ revolution after the town declared itself an autonomous, self-governing municipality, the government decided to equip and professionalize the existing community force, and help the 58-strong squad protect the monarch population.

But forest degradation and loss of habit impact far more than the butterflies. The biosphere reserve also serves as the main freshwater source for 5 million people in Mexico City. Its biodiverse ecosystem is home to 132 species of birds, 56 species of mammals, 432 species of vascular plants and 211 species of fungi, according to the WWF.

Why monarch butterflies, now endangered, are on the ‘edge of collapse’

Activists stress that climate change has to be tackled in order to protect the orange and black insects.

“If you’re talking 20, 30, 40 years out, we’re not going to be talking about monarchs any more,” Chip Taylor, the founder of Monarch Watch and a professor at the University of Kansas, told The Post in 2020. “The migration will disappear unless we solve climate change.”

Every year, millions of monarch butterflies migrate to the same remote stretch of forest in central Mexico, an event scientists have long considered a great wonder of the insect world. (Kevin Sieff/TWP)

Kevin Sieff contributed to this report.