The U.S. Fish and Wildlife Service (USFWS) proposed to list the monarch butterfly (Danaus plexippus), the iconic orange and black butterfly, as a threatened species and designate approximately 4,395 acres of critical habitat under the Endangered Species Act (ESA).

Citing the ongoing impacts from loss and degradation of breeding, migratory, and overwintering habitat, exposure to insecticides and effects of climate change, the threatened listing is proposed with protective regulations under section 4(d) of the Act. A ‘threatened species’ is a species likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.

Western Population in High Decline

Monarch Populations and Habitat. Source: Xerces Society https://journeynorth.org/monarchs/featured/monarch-butterfly-distribution-map

Compared to the Eastern monarch population, the Western monarch population is facing greater decline and environmental threats. The draft states: “In its current condition, the Western migratory population has a probability of extinction of less than 10 percent over the next 10 years. The Western migratory population has a higher risk of extinction due to current threats, with a probability of extinction of 60‒68 percent over the next 10 years…Looking across the range of future conditions for which we can make reasonably reliable predictions, the probability of extinction for the Eastern migratory population is estimated to be 24‒46 percent in 30 years and 56‒74 percent in 60 years. The probability of extinction for the Western migratory population is estimated to be 92‒95 percent in 30 years and reaches 99 percent in 60 years.”

The decline and threats to the Western population can be highly attributed to climate change. The draft states, “the Western population is vulnerable to catastrophic losses due to both widespread drought events and the co-occurrence of poor environmental conditions [such as extreme weather events or temperature] and low population abundance.”

East vs West, the Population Divide

Distinctions are made by USFWS between the Eastern monarch populations and the Western monarch population. Although not distinguished genetically, the population’s morphology, habitat and threats are the primary differentiators. A third subset, “non-migratory” monarchs are also identified by USFWS.

Nonmigratory monarchs are not likely to go extinct due to their widespread nature and ubiquity around the globe. However, likelihood of nonmigratory population growth to support migratory populations is low, due to nonmigratory populations of monarch butterflies building up high levels of a protozoan parasite, Ophryocystis elektroscirrha (OE). “In California, about 8 percent of migratory monarch butterflies are infected with OE, compared to about 75 percent of residents [nonmigratory] (Satterfield et al. 2016, p. 346). Similarly, for the eastern North American population, less than 10 percent of migratory monarch butterflies are infected with OE, compared to 75–100 percent of nonmigratory monarchs in Florida (Altizer and de Roode 2015, p. 91).”

Monarch Butterfly (Danaus plexippus) Source: USFWS https://www.fws.gov/species/monarch-danaus-plexippus

Climate Change as a Driver

Climate change is identified as a significant driver for the decline in monarch populations. The draft notes, “the Western population is vulnerable to catastrophic losses due to both widespread drought events and the co-occurrence of poor environmental conditions [such as extreme weather events or temperature] and low population abundance.”

New geographies shifted due to climate change that have potential to sustain monarch habitat are not expected to host monarch populations. The draft reads, “in western North America, climate change is predicted to cause a significant change in the distribution of overwintering monarchs in coastal California (Fisher et al. 2018, p. 10). While modeling projections suggest an inland and upslope displacement of suitable overwintering conditions by the year 2050, the best available evidence does not indicate that monarchs would move to or use these upslope areas (Fisher et al. 2018, pp. 10, 13–14).”

Critical nectar resources and access to milkweed are also expected to decline due to climate change. The draft notes that, “with a warming climate, drought impacts may affect the availability of nectar sources, especially in the western population and in the migratory bottleneck through Mexico… The reduced amount of breeding and migratory habitat continues to negatively impact the viability of the migratory North American monarchs. Monarch conservation needs an approach that encourages and incentivizes landowners to add milkweeds and nectar resources and implement actions to maintain this habitat.”

Farming Critical to Support

Farmers have demonstrated that agriculture and pollinator conservation work hand in hand. USFWS acknowledges that, “private landowner and general public support are crucial because the species is wide-ranging and needs broad conservation action, from small- to large-scale efforts, throughout its range.”

To improve future conditions that would allow monarch migratory populations to stabilize and grow, USFWS suggests that there is a need to “(1) achieve a significant increase in the availability of milkweed and nectar plants in monarch breeding and migratory areas; (2) protect and enhance overwintering habitat; (3) avoid and minimize impacts to monarchs and their habitat from insecticides and herbicides; and (4) maintain public support for the conservation of monarch butterflies.”

Next Steps

USFWS will hold two public informational meetings followed by public hearings. The first meeting and hearing will be from 6:00 p.m. to 8:30 p.m., eastern time, on January 14, 2025. To accommodate those in western time zones, the second meeting and hearing will be from 8:00 p.m. to 10:30 p.m., eastern time, on January 15, 2025

• FAQ
• Public comments can be submitted until March 12^th, 2025.
  • Submit comments online by searching for docket number: FWS–R3–ES–2024–0137
• Full draft of the proposed listing