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Eastern Monarch Butterfly Population Decreases In the 2022-2023 Overwintering Season

Mar 20, 2023


  • Population Trends
  • Important Monarch News

 St. Paul, Minnesota, March 21, 2023- The presence of monarch butterflies in Mexico’s oyamel fir forests this past winter was 22% less than the previous year, according to the most recent survey led by the World Wildlife Fund (WWF) Mexico. Monarch butterflies occupied 2.21 hectares, 0.63 less than the 2.84 hectares in the 2021-2022 overwintering season.

The eastern monarch butterfly population is surveyed most comprehensively during this overwintering period. Because it is too difficult to count individual monarchs, the population is estimated by the area they occupy (in hectares). Each hectare is approximately 2.47 acres. Semmens et al., 2016 established a recommended threshold of at least 6 hectares of overwintering monarchs to sustain the eastern population and its migration. While populations fluctuate annually, the long-term decline continues to be of great concern and in need of conservation action.

Monarch butterflies face many threats, but through widespread, collaborative, and ongoing conservation action, we can support their recovery. Supporting and sustaining the monarch migration will take a unified effort across all land use sectors in North America. The Monarch Joint Venture supports monarch and pollinator conservation planning and implementation efforts on a broad scale by facilitating information sharing, partnership building, and carrying out identified conservation priorities within its Monarch Conservation Implementation Plan. With over 120 partners, ranging from federal and state agencies to non-governmental organizations, businesses, and academic programs, the MJV partners to protect the monarch migration across the United States. The MJV’s work leverages partnerships and the charisma of the monarch butterfly as a flagship for broader conservation benefits.

Individuals and communities can support monarchs in various ways, including planting milkweed and nectar resources, joining a monarch community science project, engaging your community and elected officials, or contributing to conservation financially.


Read the annual survey, Forest Area Occupied by Monarch Butterflies Colonies in Mexico During the 2022-2023 Hibernation Season here.

Read the recent study, Forest Degradation at the Core Zone of the Monarch Butterfly Biosphere Reserve (2021-2022) here

Read the WWF- Mexico news release here

Read the WWF Blog Post here

Are you curious about how researchers measure the eastern monarch population in Mexico? Learn about the process here.

Read this year's 2022-2023 western monarch population announcement here.

Read last year's 2021-2022 eastern monarch population announcement here.

The Monarch Joint Venture is a 501c3 nonprofit organization and a national partnership of federal and state agencies, non-governmental organizations, businesses, and academic programs working together to conserve the monarch butterfly migration. The content in this statement does not necessarily reflect the positions of all Monarch Joint Venture partners.