Skip to main content

Number of Monarchs Overwintering in Mexico Falls by 50 Percent

Monarchs are not recovering and still urgently need Endangered Species Act protection in the United States and extraordinary conservation efforts.


Expert Contacts:

Scott Black, Executive Director, Xerces Society for Invertebrate Conservation

(503) 449-3792 |  [email protected]

Emma Pelton, Conservation Biologist—Western Monarch Lead, Xerces Society for Invertebrate Conservation

(971) 533-7245 |  [email protected] 

PORTLAND, Ore., March 13, 2020—The World Wildlife Fund-Mexico and the Comisión Nacional de Áreas Naturales Protegidas (CONANP) announced today that monarchs in central Mexico occupied an estimated 2.83 hectares of forest during the winter of 2019–2020. Last year, monarchs occupied 6.05 hectares, a reduction of approximately 53 percent. Read more in English here, and in Spanish here.

It is clear from this announcement that monarchs are not recovering and still urgently need Endangered Species Act (ESA) protection in the United States and must remain the focus of extraordinary conservation efforts. Climate change, pesticide use and habitat loss in both Mexico and the United States continue largely unabated, and threaten both the eastern monarch population (which overwinters in Mexico) and the western population (which primarily overwinters in California).

The western population, whose numbers were reported recently, remains critically imperiled. This season’s Xerces Society’s Western Monarch Thanksgiving Count  and New Year’s Count have revealed that the migratory monarch population which breeds west of the Rocky mountains continues to hover at less than 1 percent of its historic population size for a second year in a row, whereas this year’s eastern population represents approximately one-third of its historic size.

The US Fish and Wildlife Service will make a decision about whether to list monarchs under the ESA in December 2020. The best science recommends the eastern population needs to sustain an overwintering size greater than 6 hectares over many years. Clearly, the work to recover monarchs is far from over.

To restore monarch populations across North America and ensure these butterflies’ incredible migration continues, everyone can help make a difference. We recommend creating and protecting habitat, reducing or eliminating pesticide use, contributing to community science projects, and supporting other monarch conservation efforts.

At Xerces, we work with farmers, roadside managers, and communities to protect, restore and manage habitat for monarchs. We have restored over a million acres for pollinators, including monarchs, at sites across the United States. We also focus on the protection and restoration of overwintering sites in California and their migratory and breeding areas across the West.

Learn more about our work and how to help monarchs here.


Learn more about monarch conservation nationwide:

Learn more about helping western monarchs:

Xerces is partnering with Ink Dwell studio to educate and inspire people to take action for monarchs. Read more in an article in Wings magazine or at



The Xerces Society is a nonprofit organization that protects the natural world by conserving invertebrates and their habitat. Established in 1971, the Society is a trusted source for science-based information and advice and plays a leading role in promoting the conservation of pollinators and many other invertebrates. We collaborate with people and institutions at all levels and our work to protect bees, butterflies and other pollinators encompasses all landscapes. Our team draws together experts from the fields of habitat restoration, entomology, plant ecology, education, farming and conservation biology with a single passion: Protecting the life that sustains us.

To learn more about our work, please visit or follow us @xercessociety on Twitter, Facebook or Instagram.