Over the past 20 years, scientists have noted declines in North American monarchs overwintering in Mexico and California where these butterflies cluster. Numbers in the larger eastern population are measured by the size of the area they occupy. At a density of roughly 8.5 million monarchs per acre, it is estimated that the eastern population fell from about 384 million in 1996 to a low of 14 million in 2013. The population in 2019 was about 60 million. The western population, located in California, saw a more precipitous decline, from about 1.2 million in 1997 to fewer than 30,000 in 2019.

In 2014, the Service received a petition to list the species and published a substantial 90-day finding in December 2014. In 2016, the agency began an in-depth status assessment, looking at the global population as well as focusing on monarchs in North America, where 90% of the world’s population occurs.

The ESA provides for a warranted-but-precluded finding when the Service does not have enough resources to complete the listing process because the agency must first focus on higher-priority listing rules. Warranted-but-precluded findings require subsequent review each year until the agency undertakes a proposal or makes a not-warranted finding.

The Service prioritizes work on imperiled species through its National Listing Workplan. Currently, listing actions for 161 species on the workplan (64%) are a higher priority than the monarch. These species include plants, insects, freshwater mussels, fish, birds, and mammals. Obligations to meet court orders and settlements due to litigation can affect when the agency works on some species.

Robust conservation efforts are ongoing across the continent, including partnerships with states, tribes, Canada and Mexico, local communities, and conservation organizations, to address threats to the monarch and to bolster milkweed abundance and other habitat needs.

"The Monarch Joint Venture is committed to continuing its conservation efforts for monarchs. Each of our partners, and many other stakeholders, come to the monarch conservation table with different approaches, audiences, strengths, and opportunities to make a difference. There is a role for everyone in monarch conservation,” stated Wendy Caldwell, Executive Director, Monarch Joint Venture.

The Midwest Association of Fish and Wildlife Agencies (MAFWA), working with state agency partners in the northeast and south-central US, created the MidAmerica Monarch Conservation Strategy to address monarch issues in the Midwest and the Northeast United States. Similarly, the Western Association of Fish and Wildlife Agencies (WAFWA) created a working group to develop a plan for monarch conservation.

“The Association of Fish and Wildlife Agencies has been working side-by-side with the U.S. Fish and Wildlife Service on voluntary monarch butterfly conservation since 2014. We’ve made great strides, including raising awareness and restoring key habitat, but we still have a long way to go for a sustainable, long-term impact. Moving forward, we’ll continue to be a close partner in our collaborative efforts to restore this iconic species,” stated Sara Parker Pauley, Director of the Missouri Department of Conservation and President of the Association of Fish and Wildlife Agencies in the FWS press release.

Concerns with the population size of the western population of monarchs remain heightened following the unusual year of drought and fires in the western states and a disappointing count of monarchs at traditional monarch wintering sites. Estimates from the survey of monarch wintering sites in Mexico have yet to be made available.

By Bill Moritz; Excerpted from various press releases including the U.S. Fish and Wildlife Service press release on December 15, 2020.