Washington, D.C. — In a new study published in Frontiers in Ecology and Evolution, a team of scientists from NatureServe has unveiled detailed maps identifying migratory habitats essential to western monarch butterflies, revealing a critical insight: despite federal management over half of the land in the western United States, the vast majority of suitable habitat lies on private lands. This finding emphasizes that federal efforts alone are not enough; coordinated conservation initiatives that engage private landowners are vital to protect this iconic species.
The migratory monarch butterfly (Danaus plexippus plexippus) is known for its iconic migrations in North America. The population east of the Rocky Mountains mostly migrates to central Mexico to overwinter. West of the Rockies, most monarchs migrate to overwintering sites along the California coast. This new research, which focused on western monarchs, addresses a critical gap in our understanding of where conservation efforts for these butterflies would be most effective.
“Previous models have provided a general sense of where monarchs might be found, but our new high-resolution models, combined with land stewardship information, offer detailed insights that can directly inform land management decisions,” said Dr. Bruce Young, Chief Scientist for NatureServe. “This information is vital for anyone involved in conservation efforts, from federal and state agencies to NGOs and private landowners.”
Western migratory monarchs (Danaus plexippus plexippus). NatureServe Global Status: Vulnerable Subspecies (T3). Photo by Lisa Hupp, U.S. Fish & Wildlife Service.
Unraveling the Monarch’s Journey
Migratory species like the monarch butterfly present unique conservation challenges. Their populations face myriad threats across different geographic areas, often far removed from each other. As these animals travel across a vast landscape over multiple generations, understanding when and where they need protection becomes a complex puzzle.
This study sought to solve part of that puzzle by modeling suitable habitat for western monarchs during their spring and fall migrations. The resulting maps, derived from advanced modeling techniques, are the first to offer such precise information at a scale useful to land managers.
“The advanced modeling approach used for this study is not just limited to monarchs,” said Dr. Patrick McIntyre, Director of Ecology for NatureServe. “It could be adapted to support the conservation of other migratory animals facing similar threats.”
Key Findings from the Study
The study’s findings are as detailed as they are impactful. The research reveals that environmental predictors of habitat suitability vary significantly with the seasons to reflect the butterfly’s lifecycle. For instance, climate plays a crucial role in determining suitable habitat in March and April, while in late spring and early summer, the abundance of milkweed—the monarch’s host plant—becomes the dominant factor. In the fall, nectar availability and climatic water deficit—a measure of moisture availability—become critical.
The study also highlights the stewardship responsibility for these habitats. Nearly 85% of spring and over 70% of fall migratory habitat is on private lands, especially in river valleys that are prized for agricultural production, underscoring the need for outreach and education efforts targeted at private landowners. Federal agencies like the Bureau of Land Management (BLM) and U.S. Forest Service manage important tracts of monarch migratory habitat but cannot tackle this conservation challenge alone.
Western monarch caterpillar on its host plant, milkweed.
“By breaking down the habitat ownership, we can see exactly who needs to be involved in conservation efforts,” said Hannah Ceasar, Spatial Analysis Program Manager for NatureServe. “It’s not just about identifying the habitat; it’s about making sure the right people have the right tools to protect it.”
Turning Knowledge into Action
The implications of these findings are far-reaching. The maps provide a practical guide for land managers, enabling them to identify the most crucial times and places for conservation actions. For example, managers can use these maps to determine when to avoid disruptive activities like mowing or controlled burns and where to focus restoration efforts or efforts to reduce pesticide use. By providing sustainable management solutions, this paper contributes to global efforts such as the United Nations Sustainable Development Goal 15 to conserve Life on Land.
The maps above reveal the results of habitat suitability modeling for western migratory monarch populations during the migratory seasons.
This study also arrives at a pivotal moment, as the BLM announced a new Public Lands Rule in April 2024 that places conservation on equal footing with other activities such as energy development or ranching when determining uses of the lands under their management. This rule provides BLM land managers with additional support for actions that benefit at-risk plants and animals such as the western monarch butterfly.
Charting the Path Forward
The research team hopes that these insights will inspire collaborative conservation efforts. Restoration efforts that prioritize native milkweeds, nectar plants, and habitat protection are essential, especially given the predominant role of private lands in monarch conservation, as are reductions in pesticide use in habitats used by monarchs. This research was only possible due to the thousands of monarch sightings posted by members of the public and shared by organizations participating in the Monarch Joint Venture conservation effort. Ongoing research and monitoring are encouraged to help landowners assess monarch use of their lands before committing to enhancements.
This study marks a significant advancement in our understanding of the migratory habitat of western monarch butterflies. Providing detailed, actionable information equips conservation practitioners with the knowledge they need to make informed decisions that will help reverse the decline of this iconic species.
“Studies like this demonstrate how cutting-edge applied science can bridge gaps in understanding and action,” said Dr. Anne Bowser, CEO of NatureServe. “This research reveals a critical truth in conservation: no single entity can tackle the challenges facing migratory species like the western monarch alone.”
The full paper is available in the journal Frontiers in Ecology and Evolution. This project is made possible through a grant from the National Fish and Wildlife Foundation, with support from The Bureau of Land Management.
About NatureServe
For 50 years, NatureServe has been the authoritative source for biodiversity data throughout North America. To protect threatened biodiversity, NatureServe works with over 60 organizations and 1,000+ conservation scientists in the U.S. and Canada to collect, analyze, and deliver standardized biodiversity information, providing comprehensive spatial data to meet both regulatory and conservation needs. NatureServe and its network partners develop and manage data for over 100,000 species and ecosystems, answering fundamental questions about what exists, where it is found, and how it is doing. Visit www.natureserve.org to learn more.