Size of Monarch Overwintering Population Underscores Continued Need for Conservation in the Midwest and North America

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Steve Bradbury & David Nistler
Natural Resource and Ecology Management & Entomology
Iowa State University &

The World Wildlife Fund, Comisión Nacional de Áreas Naturales Protegidas and the Monarch Butterfly Biosphere Reserve released its 2020-2021 overwintering monarch population report on February 25, 2021. Adult monarch butterflies covered approximately five acres of forest canopy in Mexico, an area about two acres smaller than last year. Scientists estimate a long-term average of 15 acres of occupied forest canopy is needed to sustain the eastern North America monarch population and its continental migration. The report notes loss of habitat in the United States, forest degradation in Mexico, and extreme weather events contribute to the population decline over the last 25 years.

The over-wintering report was preceded by the United States Fish & Wildlife Service (FWS), Endangered Species Act listing decision published on December 15th 2020. The FWS concluded that adding the monarch butterfly to the list of threatened and endangered species is warranted but is currently precluded by work on higher-priority listing actions. With this decision, the monarch becomes a candidate for listing in 2024. At this time, the FWS recommends continued implementation of voluntary conservation efforts within the upper Midwest. Conservation efforts that establish new breeding habitat are of prime importance.monarchs

Iowa Monarch Conservation Consortium, facilitated by Iowa State University, Iowa Department of Natural Resources and the Iowa Department of Agriculture and Land Stewardship, is leading voluntary conservation efforts in the state, based on a strategy developed by the consortium’s 50 organizations, which include agricultural and conservation associations, agribusiness and utility companies, universities and federal agencies. The strategy guides the implementation of a voluntary, statewide conservation effort based on the best available science. The consortium supports habitat improvements in rural landscapes that do not conflict with agricultural production, are sufficient in scale to support improved monarch breeding success and strive to complement other conservation programs.

“Now is a critical time for us to recognize the importance of providing habitat for monarchs to help minimize the decline in population,” said Kayla Lyon, director of the Iowa Department of Natural Resources. “Together, we can all do our part to provide the necessary habitat for these butterflies by simply planting milkweed or other native wildflowers not just on large landscapes but even in our backyards and planters. We are proud of our continued partnerships that focus on providing this habitat on a larger scale on our publicly managed lands.”

The monarch butterfly faces many challenges including the loss of milkweed and nectar plant habitat in its spring and summer breeding ranges. Female monarchs lay eggs exclusively on milkweed plants and caterpillars also feed solely on milkweed leaves, though adult monarchs feed on nectar from a variety of flowering plants. Habitat restoration and reconstruction should include a diverse array of milkweed and blooming species to provide nectar for adult monarchs throughout their full life cycle, including spring and fall migrations. The current Iowa Monarch Conservation Strategy seeks to establish approximately 480,000 to 830,000 acres of monarch habitat by 2038.

"We’re working with public and private partners to ramp up conservation efforts around the state to improve the health of our soils, protect our water sources, and preserve the monarchs that play a critical role in our ecosystem,” said Iowa Secretary of Agriculture Mike Naig. “I encourage everyone to look for opportunities to layer conservation practices, like buffer strips and milkweed, to maximize the environmental benefits while creating habitats for monarchs and other wildlife.”

”Research at Iowa State has improved our understanding of what it takes to establish and enhance habitat to sustain the monarch,” said Daniel J. Robison, holder of the Endowed Dean’s Chair in the College of Agriculture and Life Sciences at Iowa State. “Our research findings and on-going extension efforts, in coordination with other state and national partners, helps ensure science-based information guides our conservation practices in Iowa and the greater Midwest.”

Consortium members have collaborated with Iowa State University Extension and Outreach to develop several free publications including, “5 Ways to Help the Monarchs” and “Enhancing Monarch Butterfly Conservation in Iowa.” Additional resources can be found by visiting or following or

Date of Publication: 
March, 2021