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IUCN Changes Migratory Monarch Status from Endangered to Vulnerable

Dec 11, 2023


  • Community Science
  • Population Trends
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On December 30, 2021, the International Union for the Conservation of Nature (IUCN) added the migratory monarch butterfly (Danaus plexippus) to the Red List of Threatened Species as endangered. In June 2023, the IUCN Standards and Petitions Committee received a petition regarding their listing of the migratory monarch butterfly. The petition challenged the appropriateness of population models used in its assessment over the past ten years. After much deliberation, the Standards and Petitions Committee announced on September 27, 2023, that the IUCN would change their listing of the migratory monarch butterfly from endangered to vulnerable on December 11, 2023.

The primary reason for the shift in status was not due to a change in the current status of migratory monarchs. Many methods exist for examining population trends over time, all of which are complex, especially for a migratory insect with a broad geographic range. IUCN-specified criteria are based on the level of population reduction over the past 10 years or three generations, whichever is longer. In the original review, population data demonstrated a long-term population decline in migratory monarchs over multiple decades. When re-evaluated per IUCN criteria, the population decline within the last 10 years did not match the decline of the longer-term trend. Therefore the review warranted a change in IUCN status to be congruent with its evaluation criteria. Both methods of population evaluation used were scientifically valid. The monarch's IUCN status change highlights science's dynamic nature and the imperative need for continuous data collection and evaluation.

Below are frequently asked questions regarding the status of monarchs and monarch conservation efforts. If you have further questions after reviewing the questions and resources below, please contact

What does the IUCN listing change mean for monarchs?

The status change of the migratory monarch on the IUCN’s Red List is due to a shift in the data used to evaluate the species, not due to a change in the current population. While concerns remain about the sustainability of the monarch migration, conservation efforts will persist.

Does the IUCN Red List have legal ramifications in the United States?

No, the IUCN Red List provides international recommendations and does not carry legal implications in the United States. The authority to classify the migratory monarch as endangered lies with the US Fish and Wildlife Service (USFWS).

What is the current legal status of the migratory monarch in the United States?

On December 15, 2020, the USFWS concluded that listing the monarch butterfly under the Endangered Species Act (ESA) is “warranted but precluded.” With this announcement, monarch butterflies became a candidate species. While candidate species do not have legal protections under the ESA, candidate species status highlights the need for continued monitoring, voluntary conservation, and support of the monarch population. The USFWS will review the monarch’s status each year as part of their annual Candidate Notice of Review, and if a change in status is warranted, they may take action sooner.

Are monarch populations still at risk?

Monarchs are globally distributed. These majestic butterflies are well known for their two long-distance migrating populations in North America. The eastern and western migratory monarch populations are divided by the Rocky Mountains. Each population has been monitored at their respective overwintering sites, California and Mexico, since the mid-1990s. Researchers and community scientists now estimate the eastern population has declined by more than 80% since the mid-1990s, and the western population has decreased by more than 95% since the 1980s.

What is causing monarch populations to decline?

Monarchs face many threats and stressors that result in declining populations in both the eastern and western regions of their North American range. The most significant impacts come from habitat loss for breeding, migrating, and overwintering. In addition, indiscriminate use of chemicals to control insects and weeds can have harmful unintended consequences for monarchs; a changing climate is making some habitat less suitable and forcing changes in migratory patterns; and monarchs face many risks from natural enemies such as predators, parasitoids, and diseases.

How can I support monarchs?

Supporting monarchs requires a collective effort through habitat development, participation in community science projects, information sharing, advocacy, and supporting conservation organizations. Explore opportunities to contribute to nationwide efforts to protect monarchs at



Migratory Monarch Assessment Information

Migratory Monarch IUCN Status Petition Description

US Fish and Wildlife Service

About Monarchs

Species Status Assessment Fact Sheet

Monarch Butterfly Species Status Assessment (SSA) Report

Pesticide Supplemental Materials for the Monarch (Danaus plexippus plexippus) Species Status Assessment Report

Endangered Species

Environmental Conservation Online System: Monarch Butterfly

Monarch Conservation Strategies

Midwest Association of Fish & Wildlife Agencies, Mid-America Monarch Conservation Strategy

Western Association of Fish and Wildlife Agencies, Western Monarch & Native Insect Pollinator Working Group

Monarch Joint Venture’s Monarch Conservation Implementation Plan