Eastern Monarch Butterfly 2023 Overwintering Numbers Announced

On March 21, the World Wildlife Fund (WWF) Mexico announced the long-awaited overwintering population estimate of the eastern population of monarch butterflies. Counts over this past winter (2022-2023) indicated that monarch butterflies occupied 2.21 hectares, or about 5.5 acres. This represents a 22% decline relative to the 2021-2022 overwintering season. These numbers represent a roughly 88% decline compared to the highest monarch population counts on record from the mid-1990s.

But Wait, Aren’t Monarchs Rebounding?

A first glance, reports of monarch overwintering numbers can sometimes be confusing. Some reports say they're up; others down. Like any insect, monarch populations are variable. The recent differences reported are related to the two primary and geographically distinct monarch populations across North America: western and eastern.

Western monarch butterflies migrate throughout the states located west of the Rocky Mountains. Western monarchs overwinter primarily in coastal California. This population count, led by the Xerces Society, occurs between Thanksgiving and New Year’s each year. This year’s western count totaled over 335,000 butterflies – a welcome improvement over the less than 2,000 butterflies recorded in the winter of 2020.

In contrast, the eastern population migrates throughout the eastern half of North America - spanning from Mexico northward to southern Canada. The eastern monarchs overwinter in Mexico’s oyamel fir forests each winter. The eastern monarch population comprises over 90% of the global monarch population. As such, changes to this population over time are proportionally substantial in the global population of the monarch butterfly.

In the Waiting Room

A listing on the Endangered Species Act is often referred to as “the emergency room” for a species. It's where we (as a nation) triage species in danger of extinction through restrictions and focused conservation. With the announcement of the monarch overwintering numbers, we are now in the “waiting room”. Conservationists, agencies, and companies are now waiting for the USFWS to make their proposed determination on the monarch’s potential for listing under the Endangered Species Act. Will the monarch be admitted into the emergency room, sent back to urgent care, or continue in the waiting room?

USFWS previously determined that listing was warranted, but precluded in December 2020. Nearly two-and-a-half years later, USFWS is now revisiting this decision with a revised determination expected in November 2023. When considering the health of the North American monarch butterfly population, the USFWS evaluates whether the species has a sufficient population to withstand annual variation in its environment (resiliency), potential catastrophes (redundancy), and changes in its environment (representation). Within their updated species status assessment (SSA),?USFWS will consider these factors along with the positive contributions created and sustained by conservation efforts like the Monarch CCAA.

Addressing the Uncertainty

A monarch butterfly listing can have widespread repercussions for land and vegetation management throughout the country. So how can landowners and managers prepare for the uncertainty of a possible listing?

• Plant and protect milkweed and nectar plants. The recent overwintering results underscore the importance of landscape-scale conservation efforts. Monarch butterflies need an abundance of milkweed and diverse nectar plants throughout their migratory range across North America. While some land managers may want to remove vegetation to reduce regulatory risk, this is often a costly and short-sighted approach. Not only may this approach be unsustainable in practicality, it may also conflict with other land management goals for sustainability and environmental responsibility disclosures. Without milkweed and nectar plants, monarchs will continue to decline. From a regulatory perspective, this risks greater prohibitions and a prolonged listing. Engaging in proactive conservation can help species recover more quickly and reduce long-term costs associated with a listing.
• Consult with USFWS early. Federal agencies that have not done so yet should consider consultation with USFWS to determine how they can fulfill Section 7(a)(1) of the ESA and promote conservation of potential endangered and threatened species. Engaging in consultation early can help streamline agency workloads and avoid costly delays or bottlenecks.
• Engage in conservation partnerships. Monarch conservation leaders like Monarch Joint Venture, Xerces Society, and Journey North provide opportunities and resources for engaging with diverse partnerships. Efforts like the University of Illinois at Chicago’s Monarch CCAA ?program provide a specialized partnership of energy and transportation land managers that to date has resulted in over 800,000 acres of habitat commitments for the monarch butterfly.
• Explore alternative scenarios and approaches. Considering the potential regulatory risks as well as conservation and sustainability commitments can help understand and navigate the complexities of biodiversity conservation and regulatory support. At Stantec, our team of monarch conservation experts and endangered species specialists can assist in scenario planning and navigating the uncertainty of a possible listing.

Learn More About the Overwintering Monarch Population Counts:

World Wildlife Fund announcement on the 2022-2023 eastern monarch population overwintering count: https://www.worldwildlife.org/stories/troubling-news-for-monarch-butterfly-populations

Xerces Society’s announcement on the 2022-2023 western monarch population overwintering count: https://xerces.org/press/western-monarch-count-tallies-over-330000-butterflies

Journey North’s announcement on the 2022-2023 eastern monarch population overwintering count: https://journeynorth.org/monarchs/news/spring-2023/03202023-get-ready-monarch-movement