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What Is Really Killing Monarch Butterflies?


Assistant Research Scientist Andy Davis is featured in a story in Scientific American exploring the debate about what’s behind declines in monarch butterfly populations at their overwintering sites in Mexico.

What Is Really Killing Monarch Butterflies?
Some scientists suspect that Roundup and milkweed loss aren’t the only culprits
By Gabriel Popkin
Scientific American (subscription required)
March 1, 2020image

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Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at Scientific American maintains a strict policy of editorial independence in reporting developments in science to our readers.

2 Butterfly Defenders Found Dead Within a Week in Mexico


The funeral of Mexican butterfly defender Homero Gómez González, one of two men connected with a monarch sanctuary found dead last week. ENRIQUE CASTRO / AFP via Getty Images

Two men connected to a famous monarch butterfly reserve in Mexico have been found dead within a week of each other, raising concerns for the safety of environmental activists in the country.

Homero Gómez González, 50, who managed a butterfly reserve in Mexico’s Michoacán state and campaigned against illegal logging in the butterflies’ winter habitat, was found dead in a well on Jan. 29, BBC News reported. Three days later, part-time reserve tour guide Raúl Hernández Romero, 44, was also found dead on top of a hill in the El Campanario monarch butterfly sanctuary.

“How can you protect the butterflies if Homero Gómez or other people are not protected?” poet and environmental activist Homero Aridjis asked NPR.

Gómez González managed the El Rosario sanctuary, which is part of the Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage site. The site, located in forested mountains around 100 kilometers (approximately 62 miles) northwest of Mexico City, is where more than half of eastern monarch butterfly colonies spend their winters. The butterflies travel all the way to Canada each spring and then back again in the fall. Because four generations of butterflies are born and die during this time, it is unclear how they know to find their way back, but they do.

“Every autumn, millions, perhaps a billion, butterflies from wide areas of North America return to the site and cluster on small areas of the forest reserve, coloring its trees orange and literally bending their branches under their collective weight,” UNESCO described.

But the butterflies’ winter home is threatened by logging and the planting of avocado farms, according to NPR. Between 2005 and 2006, loggers felled 461 hectares in the area, The Washington Post reported.

Gómez González, a former logger himself, campaigned to protect the reserve and argued that tourism from the butterfly migration was worth more to the region than illegal logging. The El Rosario sanctuary he managed opened in November to help prevent logging, BBC News reported, and his family said he received threats before he disappeared Jan. 13.

His funeral on Friday was widely attended.

“I offer my condolences to Mr. Gómez González’s family, his colleagues and all of those who, in Mexico and elsewhere, sometimes at the risk of their lives, work every day to protect this natural heritage which is shared by all of humanity,” Director of the World Heritage Centre Mechtild Rössler said in a statement.

Gómez González was found to have received a blow to the head before drowning in a well, BBC News reported. His death was apparently not a robbery, since he was found with the equivalent of more than $500 in pesos, according to NPR.

Hernández Romero worked showing tourists around the El Rosario sanctuary, according to The Washington Post.

He was last seen Jan. 27 leaving his home, and then found dead Saturday after having been badly beaten with a sharp object.

Authorities are unclear if the deaths are connected to each other or to both men’s work protecting the butterflies. However, The Guardian pointed out that there is a trend of environmental defenders being murdered in Mexico in conflicts with developers or criminal groups. Mexico’s murder rate is also generally on the rise, BBC News reported. In 2019, the country saw its highest murder rate ever with 34,582 reported killed.

Second man with ties to Mexico’s largest monarch butterfly reserve found dead

By Kevin Sieff
Feb. 2, 2020 at 6:19 p.m. CST
MEXICO CITY — Authorities are investigating the death of a part-time tour guide in one of Mexico’s largest butterfly sanctuaries — the second person connected to the reserve found dead in less than a week.
The body of Raúl Hernández Romero, 44, was found badly beaten with a sharp object on Saturday. The body of local politician Homero Gómez González, a well-known defender of the monarch butterfly sanctuary in Michoacan state was recovered last week after a two-week disappearance.
Hernández Romero was last seen Jan. 27 leaving his home in the municipality of Angangueo. His wife reported the disappearance to local authorities, who were then still searching for Gómez González.
Officials said they were uncertain of any connection between the two deaths, or between their deaths and their work in environmental conservation.

For years, illegal loggers tied to Mexico’s criminal underworld have clashed with conservationists who tried and eventually succeeded to ban logging from the butterfly sanctuaries in the state of Michoacan.


Between 2005 and 2006, 461 hectares in the region were lost to illegal logging. The destruction threatened the world’s largest butterfly migration.


Gómez González, a former logger himself, spoke out against the threat of illegal timber. Millions of butterflies travel thousands of miles from the United States and Canada each year to winter on a few hillsides in Michoacan, a spectacle that draws thousands of tourists annually.


Homero gomez g.@Homerogomez_g

En el Santuario El Rosario Ocampo Michoacan “ El más grande del mundo “

Embedded video

Gómez González, a former commissioner of the small community of Rosario, and other local leaders argued that tourism could produce a more sustainable revenue stream than logging. The Monarch Butterfly Biosphere Reserve was named a UNESCO World Heritage Site in 2008.

Hernández Romero was one of the men who showed Mexican and foreign tourists around the Rosario sanctuary. He pointed out the massive clusters of monarchs that hung from oyamel trees and scattered in an orange cloud when they were touched by the morning light.


Magdalena Guzmán, a spokeswoman for the Michoacan attorney general’s office, said authorities were “looking into several lines of investigation” in the deaths of the two men, including their connections to the butterfly sanctuary.



Gómez González’s death sent a shock wave through the community of environmentalists in Mexico and beyond. For many, it underscored the risks involved with activism in Mexico, where organized crime and conservation are often at odds.

Gómez Gonzále

z’s body was found at the bottom of a well on Wednesday. Hundreds of farmers and agricultural workers attended his funeral Friday, the Associated Press reported.

Mourners carry the coffin of Mexican environmentalist Homero Gómez González during his funeral procession Friday in Michoacan state, Mexico.
Mourners carry the coffin of Mexican environmentalist Homero Gómez González during his funeral procession Friday in Michoacan state, Mexico. (Enrique Castro/AFP/Getty Images)

So far, authorities say, no evidence links his death to his work defending the monarchs.

Mexican president Andrés Manuel López Obrador called Gonzalez’s death “very unfortunate and painful.”



The cause of Romero’s death is also unclear. Many here doubt the crimes will ever be solved.


According to the National Institute of Statistics and Geography, 154,557 people were killed in Mexico between 2010 and 2016. There were convictions in fewer than 6 percent of those cases.


“All of these losses are horrible,” said Gloria Tavera, the regional director for the commission of national protected areas. “All of these people are important.”

Headshot of Kevin Sieff

Kevin Sieff has been The Washington Post’s Latin America correspondent since 2018. He served previously as the paper’s Africa bureau chief and Afghanistan bureau chief. Follow

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