How the climate crisis is killing Mexico’s butterflies

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

But in just one year, the population of monarch butterflies wintering in those hillsides dropped 22 per cent, 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 12C and the low 20s when they migrate, an abundance of milkweed when they mate, and some rain during the winters.

But climate change has scrambled the consistent weather patterns they rely on, and more butterflies are dying. Monarch butterflies are known as experts in 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 per cent of agricultural food production depending on pollinators like monarchs, when people help the species, we are also helping ourselves.”

open image in gallery

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 population has declined steadily over the past 25 years, mostly because of a huge loss of habitat in the biosphere reserve. Between March 2021 and April 2022, the loss of monarch-friendly forest in the reserve tripled from 46.2 acres to over 145 acres, Gloria Tavera, conservation director of Mexico’s Commission for National Protected Areas, told the Associated Press.

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.

Some conservationists think that loss of habitat in Mexico is leading many of these eastern monarch butterflies, which reside in the northeast US and southern Canada, to winter instead along the West Coast of the US. More than 330,000 butterflies were tallied in California and Arizona this year, the highest number in the last six years.

open image in gallery

A possible explanation is that many of the monarchs that usually winter in Mexico are now choosing to migrate with their western counterparts, which have long wintered along the West Coast, Emma Pelton, a conservation biologist at the Xerces Society, told CBS News.

“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,” Pelton said.

Droughts, frost and “extreme temperatures” across the US 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 events have 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.

open image in gallery

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

In 1998, the residents of the Crescencio Morales farming community set fire to monarch butterfly habitats to make space to log the land, village leader Erasmo Alvarez Castillo said.

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 was a former logger who became a conservationist and was one of central Mexico’s most prominent defenders of the monarch butterfly. In a December 2019 interview, 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 us, 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.

open image in gallery

On 23 January 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 professionalise the existing community force, and help the 58-strong squad protect the monarch population.

Illegal logging continues to plague the Monarch Butterfly Biosphere Reserve, but Crescencio Morales – once home to the region's worst illegal logging – has seen numbers drop by 3.4 per cent this year.

But forest degradation and loss of habit impact far more than the butterflies. The biosphere reserve also serves as the main freshwater source for five 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.

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 anymore,” Chip Taylor, the founder of Monarch Watch and a professor at the University of Kansas, told us in 2020. “The migration will disappear unless we solve climate change.”

© The Washington Post