LINCOLN, Neb. (DTN) -- Two conservation groups argue in a new lawsuit that a continued delay in implementing federal protections for the monarch butterfly is increasing its chances of extinction and are seeking a binding date for the U.S. Fish and Wildlife Service to finalize federal protections.

Last year, the USFWS opened a new 60-day comment period that ran through May 19, 2025, on a proposed rule to list the monarch as a threatened species. That was an extension of a comment period that previously ended on March 12, 2025.

Instead of issuing the final listing at the end of 2025, the USFWS delayed the decision as a long-term action but offered no definitive date for issuing the rule.

The Center for Biological Diversity and the Center for Food Safety said in a lawsuit filed in the U.S. District Court for the Northern District of California, that "On Dec. 12, 2024, over 10 years after receiving the centers' ESA (Endangered Species Act) listing petition, the service proposed to list the monarch butterfly as a threatened species under the ESA," the centers said in its complaint filed on Thursday.

"Concurrently with the proposed rule, the service proposed designating 4,395 acres of critical habitat in Alameda, Marin, Monterey, San Luis Obispo, Santa Barbara, Santa Cruz and Ventura counties, California. The deadline for issuing a final listing rule and critical habitat designation was due a year from the proposed rule or Dec. 12, 2025. Therefore, the deadline for publishing the final listing rule has passed."

The monarch has been at the center of numerous lawsuits filed by environmental and conservation groups across the years, focused on protecting species from agriculture chemicals including glyphosate, Enlist Duo and others.

In 2024, the USFWS said the proposal came about as the monarch's population numbers have been declining.

In North America, monarchs are grouped into two long-distance migratory populations including the eastern and western migratory population.

The eastern is the largest and overwinters in the mountains of central Mexico. The western population primarily overwinters in coastal California.

According to the USFWS, over 4.5 million western monarchs flocked to overwintering grounds in coastal California in the 1980s. In the mid-1990s, an estimated 380 million eastern monarchs made the long-distance journey to overwintering grounds in Mexico, completing one of the longest insect migrations in the world.

"Today, the eastern migratory population is estimated to have declined by approximately 80%," the USFWS said in its 2024 announcement.

The western migratory population has declined by more than 95% since the 1980s, putting the western population at greater than 99% chance of extinction by 2080, according to the USFWS. During this same period, the probability of extinction for eastern monarchs ranges from 56% to 74%.

The USFWS proposal includes conserving critical habitat for the species at a portion of its overwintering sites in coastal California.

In 2014, the Center for Biological Diversity, Center for Food Safety and others petitioned the USFWS seeking protection for the monarch, after the agency reported the lowest monarch count on record that year.

Todd Neeley can be reached at todd.neeley@dtn.com

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