Monarch Populations and the ESA Listing Designation

By Chris García-Hellmuth, Butterfly Coordinator, Butterfly Pavilion

Monarch butterfly ESA listing decision

Migrating monarch butterflies (Danaus plexippus) are experiencing a drastic decline in population numbers. Some populations are suffering, while others remain static. The US Fish and Wildlife Service (USFWS) have announced their decision that listing monarchs under the Endangered Species Act (ESA) is “warranted but precluded”. This means that monarchs will become a candidate species for listing under the ESA. For more information on the decision, the official press release can be found here.

Why warranted but precluded?

The decision to list monarchs as threatened or endangered has been a nuanced process for the USFWS. This listing does not mean that monarchs will never be considered for an ESA listing, just at a later date. Analyzing all of the information through a scientific lens has led them to this decision. The constraints of the ESA prevents it from considering only a specific population of monarchs from being listed. The complexity of the monarch endangerment requires a considerate approach. The USFWS has announced a proposal to be released for a monarch listing under the ESA in 2024 as long as the listing is still warranted. Monarch populations will be monitored yearly to assess the potential need for an ESA listing.

Monarchs still need our help

Every November, the Xerces Society for Invertebrate Conservation monitors all of the known overwintering sites along the California coast. The past few years have yielded counts just below 30,000 total individuals, the proposed quasi-extinction threshold for the Western population. This year, however, preliminary results indicate that the total overwintering count for all sites will not exceed 2,000 individuals. (For more information about the past overwintering counts and the difference between the Eastern and Western populations, click here)

Conservationists across the country are using this ruling as a call to action to help save monarch butterflies. Climate change, disease, and the use of pesticides and herbicides are the main threats facing the monarchs that overwinter on the West coast.

What can we do?

This listing decision invites communities to continue to work to conserve monarch butterflies. Below is a list of actions we can do to conserve this valuable species.

• Plant native milkweed and other nectar plants to promote pollinator habitat
• Reduce pesticide use in gardens, lawns, and other areas that serve pollinators
• Get involved with monarch and pollinator community science at Butterfly Pavilion and other institutions (such as Monarch Watch and Monarch Joint Venture)
• Support organizations that work to conserve monarchs

Butterfly Pavilion is constantly working to conserve monarchs and the other invertebrates that serve as the backbone to our vital ecosystems.