Are Monarch Butterflies Endangered? Status and Population Trends

What does the IUCN Red List say?

The IUCN treats the monarch at two levels. The species as a whole was assessed as Least Concern in 2022. It lives across the Americas from Canada to northern South America and has spread to Hawaii, Australia, New Zealand, Pacific islands, Atlantic islands and southern Spain and Portugal, where most populations do not migrate.

The migratory North American subspecies, Danaus plexippus plexippus, is assessed separately. In July 2022 the IUCN listed it as Endangered, a decision that made headlines around the world. A reassessment in 2023 moved it to Vulnerable, which still means it faces a high risk of extinction in the wild.

Is the monarch protected in the United States and Canada?

In the United States, conservation groups petitioned for protection in 2014. In 2020 the U.S. Fish and Wildlife Service ruled that listing was “warranted but precluded”, meaning deserved but delayed by higher priorities. In December 2024 the agency formally proposed listing the monarch as threatened under the Endangered Species Act.

The proposal estimated that the eastern population had declined by about 80% and the western population by about 95% since the 1980s. It put the chance of the eastern migratory population collapsing within 60 years at 56–74%, and for the western population at 99%. The final rule was due in December 2025 but was postponed. After a lawsuit, a court settlement in 2026 set a deadline of 2030 for the decision.

Canada listed the monarch as endangered under its federal Species at Risk Act in December 2023. In Mexico, most winter colonies lie within the Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage Site since 2008.

How many monarchs winter in Mexico?

The eastern population is too large to count one by one. Instead, each December WWF-Mexico and Mexican authorities measure the area of forest covered by the winter colonies, a series that began in 1993. Scientists then estimate numbers using the density of butterflies per hectare, often put at roughly 20 million or more.

Numbers swing from year to year with weather on the breeding grounds and during migration, but the long-term trend since the 1990s is clearly downward. A US federal strategy in 2015 set a goal of about 6 ha (15 acres) of occupied forest, roughly 225 million monarchs. Colonies have reached that size only once since then, in winter 2018–2019.

What happened to the western monarchs?

The western population has fallen even more steeply. Volunteers have counted monarchs at California’s coastal winter sites around Thanksgiving since 1997 in the Western Monarch Count, run by the Xerces Society. Researchers estimate that several million monarchs wintered on the coast in the 1980s, and well over a million were counted in the late 1990s.

By 2018 the count had dropped to tens of thousands, and in 2020 fewer than 2,000 monarchs were found. Numbers bounced back to hundreds of thousands in 2021–2023, with about 335,000 counted in 2022, then crashed again to about 9,100 in 2024 and about 12,300 in 2025, the third-lowest total on record.

Why are monarchs declining?

Scientists point to a combination of pressures rather than a single cause:

• Loss of milkweed. Monarch caterpillars eat only milkweeds. Large areas of milkweed have disappeared from Midwestern farmland as herbicide-tolerant crops allowed weeds between and around crop rows to be sprayed, and as grassland was converted to fields and buildings.
• Fewer nectar flowers. Adults need flowers along the migration route to fuel the journey and build fat for the winter.
• Pesticides. Insecticides, including widely used neonicotinoids, can harm caterpillars that feed on contaminated plants.
• Climate change and extreme weather. Droughts, heat waves and unusual storms affect milkweed growth and breeding, and severe winter storms in Mexico have killed huge numbers of resting butterflies.
• Damage to winter forests. Illegal logging and forest degradation in Mexico, and the loss or aging of coastal groves in California, reduce the shelter monarchs need.
• Losses during migration. Some studies suggest that summer breeding numbers have declined less than winter counts, which points to heavy losses on the way south, including collisions with vehicles.

Disease also plays a part. The parasite Ophryocystis elektroscirrha spreads more easily where monarchs breed all year, for example on non-native tropical milkweed planted in southern gardens.

Is there any good news?

Yes. The 2025–2026 Mexican colonies covered 64% more forest than the year before, and the latest survey of the reserve’s core zone found less forest degradation than the year before. Monitoring experts note that summer breeding numbers in parts of eastern North America have stayed fairly steady even as winter counts dropped.

Across the US, Canada and Mexico, farmers, highway agencies, cities and gardeners are planting native milkweeds and wildflowers, reducing roadside mowing and creating pollinator habitat. Monarchs breed quickly, so they can bounce back fast in good years if enough habitat remains.

To see how monarchs compare with other threatened wildlife, browse our list of endangered animals or read about the struggles of other pollinators in are bees endangered? For the migration itself, see where do monarch butterflies migrate? and the monarch butterfly profile.