Press Release

Alarming Decline in Monarch Population Justifies Immediate Action: NRDC Urges UN To Declare Mexican Butterfly Refuge “In Danger”

NRDC To Advocate for Monarchs at UNESCO’s World Heritage Committee Session in Bonn

WASHINGTON (June 26, 2015)— Advocates for monarch butterflies are heading to a World Heritage Committee meeting in Bonn, Germany, urging immediate action to increase protections for the migrating monarch butterfly population that spends the winter in Mexico’s Monarch Butterfly Biosphere Reserve, a World Heritage site. The remarkable transcontinental migration for tens of millions of monarch butterflies is at risk of disappearing, largely due to the loss of milkweed, a plant the insects’ life cycle relies on. Skyrocketing use of the herbicide glyphosate in the US and Canada is wiping out milkweed which is the only plant on which monarch butterflies lay their eggs. 

Failure by the U.S. and Canada to take immediate action to increase protections for the butterfly imperils one of the world’s most unique and outstanding natural phenomena. The United Nations Educational, Scientific and Cultural Organization’s (UNESCO) World Heritage Committee will examine the monarch issue at its upcoming annual meeting June 28 – July 8 in Bonn in light of the worrying decline in the monarch population.

“The monarch population that overwinters in Mexico has plummeted more than 90 percent in two decades—it is a perilous decline,” said Rebecca Riley, an attorney with NRDC, who is attending the UNESCO meeting in Bonn. “The drop is linked to the destruction of monarch habitat, as massive use of glyphosate in farm fields along the ‘Butterfly Highway’ through the U.S. and Canada has killed the milkweed plants monarch caterpillars need to survive. To preserve the spectacular monarch migration, we must act quickly, rather than spend years in deliberation as the crisis worsens,” said Riley.

U.S.-based NRDC filed a petition with the UNESCO’s World Heritage Committee to list the Monarch Butterfly Biosphere Reserve as a World Heritage Site In Danger in April, 2015 together with Mexican organizations Grupo de los Cien, Alternare A.C., Danaidas Conservación y Desarrollo Sustentable A.C., Telar Social México, and CostaSalvaje, and the David Suzuki Foundation in Canada. 

The petition asks UNESCO to put the reserve on the “List of World Heritage in Danger” to help spur recognition that  the U.S. and Canada must act immediately to protect the monarchs’ milkweed breeding habitat by limiting glyphosate use, and promoting programs to restore milkweed. Over 50,000 NRDC members sent messages urging UNESCO to encourage increased protections for the monarch butterfly.

“Mexico cannot save the monarch from the massive use of glyphosate in the United States and Canada. To halt the destruction of milkweed, more must be done by our neighbors to the north to conserve the butterfly so the monarch migration to Mexico not only survives but thrives,” said Homero Aridjis, president of Grupo de los Cien and a former Mexican ambassador to UNESCO who was instrumental in the agency’s designation of the Monarch Butterfly Biosphere Reserve as a World Heritage Site in 2008.

As recently as 1997, one billion monarchs overwintered at the isolated reserve after completing an annual 2,500 mile, multigenerational journey from Mexico through the United States to Canada and back, a phenomenon scientists still do not fully understand. This past overwintering season an estimated 56.6 million butterflies arrived in the reserve. This is down from a long-term annual average of 350 million. Such low numbers put the population at greater risk from other threats. For example, in 2002 inclement weather killed more butterflies than currently make up the entire population.

The primary threat to the monarch’s survival according to scientists is the skyrocketing use of glyphosate (originally marketed as Roundup), following the adoption of genetically modified glyphosate-resistant corn and soybeans. This has wiped out much of the native milkweed where monarchs lay their eggs and is the only food their larvae will eat.

As parties to the World Heritage Convention, the United States and Canada have committed to help protect such natural World Heritage sites and not to take measures that might directly or indirectly damage sites located in other countries.  The UNESCO World Heritage Committee cannot force a country to act, but it can marshal international attention to the Heritage sites and recommend “corrective measures” to ensure the conservation of a site.

A copy of the UNESCO petition can be found here:

For more detail about this issue, read NRDC Latin America Advocate Carolina Herrera’s blog:


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