[Pollinator] Eastern migratory monarch butterfly populations decrease by 59% in 2024

[Kelly Bills]

*Eastern migratory monarch butterfly populations decrease by 59% in 2024*
World Wildlife Fund

https://www.worldwildlife.org/stories/eastern-migratory-monarch-butterfly-populations-decrease-by-59-in-2024

DATE: February 07, 2024

New data detailing the abundance of the eastern monarch butterfly colonies
wintering in central Mexico's forests estimate that the species occupied
only 2.2 acres during the 2023-2024 winter season—59% less than the
previous year when scientists observed 5.5 acres. The annual survey is
undertaken by WWF and its partners including The National Commission of
Protected Natural Areas in Mexico and the WWF-TELMEX Telcel Foundation
Alliance and is considered a benchmark for the overall abundance of the
species. Experts measure the area of forest in which monarch butterflies
hibernate each winter, providing a scientific indicator of their population
status.

Scientists believe that climatic variations in the monarch's breeding areas
in Canada and the United States gave rise to high temperatures and drought,
which reduced the abundance of milkweed, the only plant in which the
butterflies lay their eggs. Land-use changes in the United States, combined
with the widespread use of herbicides, also contributed to the loss of
milkweed and other nectar plants essential to feeding adult monarchs.

"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."

This season's largest colonies were detected outside the Monarch Butterfly
Biosphere Reserve, with 0.84 acres in the Palomas sanctuary, and 0.5 acres
in the Peña Ahumada sanctuary, both in the State of Mexico. In El Rosario,
in the Sierra Campanario sanctuary, Michoacán, where the largest colony is
traditionally located, the butterflies occupied an area of 0.46 acres. Data
recorded in 2023-2024 represents the second-smallest area occupied by
monarch butterfly colonies in Mexico since 1993, when population monitoring
began, only preceded by the 1.7 acres observed in 2013-2014. The largest
recorded population was in 1996-1997, with 45 acres monitored.

Monarch butterflies migrate from southern Canada and the northern and
central United States to their overwintering sites in the mountain forests
of Michoacán and the State of Mexico, where the Monarch Butterfly Biosphere
Reserve is located, with some traveling nearly 3,000 miles.

Monarchs require a large and healthy forest mass to protect them from
winds, rain, and low temperatures that are common at night in these
forests. The health of the forests at the Monarch Butterfly Biosphere
Reserve and throughout the monarch region also help support the regional
communities, helping improve water quality in the Cutzamala System that
provides for more than 6 million people in Mexico City and its metropolitan
area. These forest ecosystems are rich in biodiversity—home to 132 species
of birds, 56 species of mammals, 432 species of vascular plants, and 211
species of fungi.

-- 

Kelly Bills *she/her*

Executive Director

Pollinator Partnership

600 Montgomery St. Ste 440

San Francisco, CA 94111

e: kelly at pollinator.org

w: pollinator.org <http://www.pollinator.org/>

o: 415-362-1137

c: 585-255-0962

[image: Pollinator Partnership logo]
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