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Monarch butterfly populations have plummeted by 59 percent

The Eastern migratory monarch butterfly has suffered a drastic decline, with populations decreasing by 59% in 2024 compared to the previous year. 

The startling figures were released following a meticulous annual survey conducted in central Mexico’s forests, where the butterflies spend their winters. 

Drastic reduction in numbers

The survey was a collaborative effort by the World Wildlife Fund (WWF) and partners including The National Commission of Protected Natural Areas in Mexico and the WWF-TELMEX Telcel Foundation Alliance. 

The researchers found that the monarchs occupied a mere 2.2 acres during the 2023-2024 winter season, a stark reduction from the 5.5 acres observed in the prior year.

This decrease has alarmed conservationists and scientists who monitor the area of forest where the monarch butterflies hibernate in each winter. This measurement serves as a crucial scientific indicator of the species’ population status. 

Contributing factors

The drastic reduction in habitat area has been attributed to climatic variations in the monarch’s breeding grounds across Canada and the United States, which have led to high temperatures and drought conditions. These adverse weather patterns have notably diminished the abundance of milkweed, the sole plant species where monarchs lay their eggs. 

Additionally, land-use changes and the widespread application of herbicides in the United States have further exacerbated the loss of milkweed and other nectar plants vital for the adult monarchs’ sustenance.

Conservation measures must be intensified

“Fewer monarchs hibernating in their traditional forest habitat in Mexico greatly concerns all of us. It’s critical that all communities, governments, non-governmental organizations, scientists, and others continue to strengthen our conservation and protection efforts to support the monarch’s unique migration,” said Jorge Rickards, general director of WWF Mexico. 

“This is not the first time we’ve observed changes in the locations of the largest monarch colonies. It’s telling us that we need to intensify conservation and restoration measures not only in the Monarch Butterfly Biosphere Reserve, but also outside of it.”

Fluctuating population numbers

The largest monarch colonies of this season were identified outside the Monarch Butterfly Biosphere Reserve, with notable areas in the Palomas and Peña Ahumada sanctuaries in the State of Mexico, and a traditionally large colony in El Rosario, Sierra Campanario sanctuary, Michoacán. 

The 2023-2024 data records the second-smallest area occupied by monarch butterfly colonies in Mexico since monitoring began in 1993, surpassed only by the 1.7 acres observed in the 2013-2014 season. The peak population was recorded in the 1996-1997 season, with an expansive 45 acres monitored.

The monarch butterfly’s migration is one of nature’s most astonishing phenomena, with some individuals traveling nearly 3,000 miles from southern Canada and the northern and central United States to their overwintering sites in Michoacán and the State of Mexico. 

Valuable forest ecosystems

These forests not only provide sanctuary for the monarchs but also support the regional communities by improving water quality in the Cutzamala System, benefiting more than 6 million people in Mexico City and its metropolitan area. Moreover, these forest ecosystems are a haven for biodiversity, home to a diverse range of species including 132 birds, 56 mammals, 432 vascular plants, and 211 fungi.

The significant decline in monarch populations underscores the urgent need for intensified conservation efforts across North America. Protecting these majestic creatures and their habitats not only preserves a fascinating natural wonder but also safeguards the ecological health and biodiversity of the regions they inhabit.

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