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Troubling News for Eastern Monarchs as Overwintering Area Declines | Xerces Society Skip to main content
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For Immediate Release, March 22, 2023

Contacts:

Sarina Jepsen, Xerces Society for Invertebrate Conservation, (971) 244-3727, sarina.jepsen@xerces.org
 

A version of this release originally appeared with World Wildlife Fund. WWF-Mexico surveys eastern monarch overwintering habitat, while the Xerces Society coordinates the Western Monarch Count.
 

The Eastern migratory monarch butterfly is at risk: new reports show a sharp population decline and a loss of habitat in the forests where they winter each year. In just one year, the presence of monarch butterflies in their wintering grounds dropped 22%, from 7 acres to nearly 5.5 acres. This is part of a mostly downward trend over the past 25 years—when monarchs once covered more than 45 acres of forest.

The news follows a cautiously optimistic report of increasing numbers of western monarchs at overwintering sites in California, before winter storms led to higher than usual losses.

"The decline of overwintering eastern monarchs in Mexico is disappointing news. We continue to see a dangerous decline in essential pollinators like monarchs," said Sarina Jepsen, the endangered species program director for the Xerces Society for Invertebrate Conservation, which manages the Western Monarch Count. "But insects can be resilient if we give them a chance. We all have to do our part by protecting existing habitat, adding native milkweed and nectar flowers to the landscape, and reducing our pesticide use at home and in agriculture."

Every year, Eastern monarch butterflies travel up to 2,800 miles from Canada and the US to their wintering sites in the forests of Mexico. There, in what is known as the Monarch Butterfly Biosphere Reserve, monarchs cluster in shelter from winds, rain, and low temperatures.

Monarchs require a vast, healthy migratory path and large, robust forests for survival through the winter. Today, the butterflies face a reduction of breeding habitat in the US due to herbicide application and land use changes as well as forest degradation in wintering sites in Mexico. Extreme weather conditions in all these ecosystems can further their decline.

“It is not just about conserving a species, it’s also about conserving a unique migratory phenomenon in nature,” said WWF-Mexico’s General Director Jorge Rickards. “Monarchs contribute to healthy and diverse terrestrial ecosystems across North America as they carry pollen from one plant to another. With 80% of agricultural food production depending on pollinators like monarchs, when people help the species, we are also helping ourselves.”

 

What science tell us

WWF-Mexico and its partners released two new reports related to the population and winter habitat of the Eastern migratory monarch butterfly. The first shows a continued population decline and the second report highlights increased forest degradation where most monarchs cluster in colonies during the winter.

The annual WWF-Mexico-led survey, Forest Area Occupied by Monarch Butterflies Colonies in Mexico, measures the area of forest in which monarch butterflies hibernate each winter, providing a scientific indicator of their population status. The 2022-2023 report shows a 22% decline in forest area when compared to last year, down from 7.02 acres to 5.46 acres this winter.

The second report, Forest Degradation at the Core Zone of the Monarch Butterfly Biosphere Reserve, found 145 acres of forest have been degraded, a major increase when compared to the 47 acres lost in the previous year.

Forest degradation impact far more than butterflies. The Monarch Butterfly Biosphere Reserve not only provides monarchs with the right microclimate for hibernation but also serves as one of the main freshwater contributors for five million people in Mexico City and its metropolitan area. Its biodiverse forest ecosystems are home to 132 species of birds, 56 species of mammals, 432 species of vascular plants and 211 species of fungi.

WWF calls on the governments of the US, Canada, and Mexico to ensure a safe and healthy future for monarchs and their habitats.
 

What you can do

Help monarch butterflies and other pollinators by planting the right species of milkweed! Use WWF's milkweed finder to find what works in your area.

Participate in a butterfly monitoring community science project.

Discover milkweed and nectar plants native to your region and plant a pollinator garden.