Population Decline

News from the Xerces Society:

Both the eastern and western migrations have experienced significant decline in a matter of decades. In the 1990s, nearly 700 million monarchs made the epic flight each fall from the northern plains of the U.S. and Canada to sites in the oyamel fir forests north of Mexico City. Now, researchers and citizen scientists estimate that there has been a decline of more than 80% in the east. In the west, the news is more dire. In the 1980s, around 4.5 million monarchs were observed in the West. In 2020, monarch surveys revealed only 2,000 monarchs, an astounding decline from the 1980s. Thankfully, in 2021, monarchs in the West rebounded slightly to nearly 250,000 monarchs, although experts still estimate the population has declined by 99.9%.

Status of the monarch:

The International Union for the Conservation of Nature listed the migratory population of monarchs as endangered on the IUCN's Red List of Threatened Species on July 21, 2022 citing climate change and habitat destruction. Learn more about the listing here.

In response to a petition to list the monarch under the federal Endangered Species Act, the U.S. Fish and Wildlife Service reviewed the status of the monarch and in December 2020, the Service determined that listing the monarch was warranted but precluded. The Service plans to review the status of the monarch again in 2024 and will make a decision about whether to list or not as a result of the 2024 review.

Threats include:

  • Loss of milkweed (breeding) habitat

  • Pesticide use

  • Climate change

  • Logging and development

To learn more about monarch decline and what you can do to help, visit www.xerces.org/monarchs or www.fws.gov/savethemonarch/.