FWS weighs endangered status for monarch butterfly

Staff reports
The Chronicle-Express

After a thorough assessment of the monarch butterfly’s status, the U.S. Fish and Wildlife Service (Service) has found that adding the monarch butterfly to the list of threatened and endangered species is warranted but precluded by work on higher-priority listing actions. With this decision, the monarch becomes a candidate for listing under the Endangered Species Act (ESA), and its status will be reviewed each year until it is no longer a candidate.

“We conducted an intensive, thorough review using a rigorous, transparent science-based process and found that the monarch meets listing criteria under the Endangered Species Act. However, before we can propose listing, we must focus resources on our higher-priority listing actions,” stated U.S. Fish and Wildlife Service Director Aurelia Skipwith. “While this work goes on, we are committed to our ongoing efforts with partners to conserve the monarch and its habitat at the local, regional and national levels. Our conservation goal is to improve monarch populations, and we encourage everyone to join the effort.”

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 Service used the best scientific information to evaluate threats to the monarch, including habitat loss, climate change and exposure to pesticides, and used a model to create millions of simulations of future conditions to estimate the risk of extinction. The agency launched a monarch conservation database and gathered vast quantities of data on existing and future conservation efforts that benefit the monarch across the continent. The resulting assessment was then peer reviewed.

After a thorough review of the best available scientific and commercial information, the Service found that listing the monarch butterfly as an endangered or threatened species is warranted but precluded by higher priority actions to amend the Lists of Endangered and Threatened Wildlife and Plants. Therefore, the Service is adding the monarch butterfly to the candidate list and assigning it a listing priority number of eight. This priority number indicates the magnitude of threats is moderate and those threats are imminent. 

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.