Eastern Monarch Numbers Increase, But Conservation Efforts Still Critical

Photo Credit: © Robert Seilheimer

Media Contact: Wendy Caldwell, Executive Director, wcaldwell@monarchjointventure.org

The eastern monarch butterfly population in Mexico’s oyamel fir forests this past winter occupied 1.79 hectares, according to the latest survey released by the World Wildlife Fund-Telmex Telcel Foundation Alliance (WWF) and the National Commission of Protected Natural Areas in Mexico (CONANP). This represents a 99% increase from last year’s 0.9 hectares in the 2023-2024 overwintering season.

Researchers survey the eastern monarch population each winter when the butterflies cluster together in their overwintering sites in Mexico. Instead of counting individual monarchs, scientists estimate the population size by measuring the area of the trees the butterflies are occupying (in hectares). Each hectare is approximately 2.47 acres or just over two American football fields. While the number of monarchs per hectare can vary, estimates suggest there are between 20-30 million monarchs per hectare (median of 21.1 million, according to Thogmartin et al., 2017). According to Semmens et al., 2016 a threshold of at least 6 hectares of overwintering monarchs is recommended to support a sustainable eastern migratory population. The current population remains below this target, highlighting the need for continued conservation action.

Monarchs face many threats and stressors that contribute to their decline. Losses in habitat necessary for breeding, migrating, and overwintering have been a significant factor, compounded by weather and climate conditions unfavorable for population growth and unintended effects of pesticide use. Monarchs also face many risks from natural enemies such as predators, parasitoids, and disease.

Given the ongoing threats to its population, the monarch butterfly's legal status has been discussed for many years. In December of 2024, the U.S. Fish and Wildlife Service proposed to list the monarch as threatened under the Endangered Species Act (ESA). While monarchs are not yet listed under the ESA, this proposal underscores the urgency of scaling up conservation efforts to support population recovery.

Conservation Efforts Are Critical

Monarch butterflies face numerous threats, but their recovery is possible through widespread, collaborative conservation action. Supporting the monarch migration requires engagement from all land use sectors across North America. The Monarch Joint Venture (MJV) plays a key role in these efforts by facilitating collaboration, sharing information, and implementing conservation strategies outlined in the Monarch Conservation Implementation Framework.

With over 135 partners—including federal and state agencies, non-governmental organizations, businesses, and academic institutions—the MJV works to conserve monarchs and the ecosystems they depend on. Our collaborative network contributes to habitat restoration, research, education, and community engagement efforts to safeguard the monarch migration for future generations.

How You Can Help

• Create Habitat for Monarchs – Monarchs cannot survive without an abundant supply of milkweed. Plant native milkweed and nectar-rich flowers to support monarchs throughout their life cycle.

• Participate in Community Science – Help researchers track monarch populations, migration patterns, and health by contributing to community science projects.

• Share Information – Share your knowledge with others so they, too, can enjoy monarchs and do their part in conserving the migration.

• Advocate – Speak up for what you care about.

• Donate – Nonprofit organizations like the MJV depend on donations and grants to continue their critical work in monarch and wildlife conservation. You can support these efforts in many ways, including shopping at our store, making monthly contributions, sponsoring programs, and more.