Monarch butterflies added to the endangered species list

Migratory monarch butterflies — the much-loved orange-and-black insects known for their impressive annual journey that takes them thousands of miles across North America — are now considered endangered.

The International Union for the Conservation of Nature (IUCN), a group headquartered in Switzerland that tracks species and extinctions, added the migratory monarch butterfly (Danaus plexippus plexippus) to its Red List of Threatened Species. The new classification, announced Thursday, comes after monarch populations on the continent have dwindled in recent decades due to habitat loss and climate change.

"Today's Red List update highlights the fragility of nature's wonders, such as the unique spectacle of monarch butterflies migrating across thousands of kilometres," Bruno Oberle, the union's director general, said in a statement.

The migratory monarch butterfly is a subspecies that breeds over the summer throughout Canada and the United States before traveling south to California and Mexico for the winter. IUCN scientists estimate that populations of the insects have shrunk 22 percent to 72 percent over the past decade.

Warmer temperatures, years of intense drought and severe wildfires — all elements that are exacerbated by climate change — are transforming the land and reducing the availability of plants that these monarchs need to breed and fuel their long migratory journeys. The insects are also affected by the overuse of pesticides and habitat loss from agriculture and urban development.

There are two types of migratory monarchs in North America: the Eastern monarch butterflies and the Western monarch butterflies.

Western monarchs, which typically breed over the summer within a narrow corridor that includes California, Nevada, Oregon and Washington state, are at greatest risk of extinction, according to the IUCN. Their numbers have fallen from as many as 10 million in the 1980s to less than 2,000 in 2021, the group said.

The larger population of eastern monarch butterflies, which typically breed over the summer across a wide swath of the United States and Canada east of the Rocky Mountains, is also declining, the scientists found. The number of eastern monarchs shrunk by around 84 percent from 1996 to 2014, according to the IUCN.

The group's Red List is used as a gauge of a species' overall health, with classifications ranging from "near threatened" to "vulnerable" to "endangered" and "critically endangered" before being considered "extinct" or "extinct in the wild." The categories are adjusted regularly, largely based on conservation initiatives and other efforts to help threatened or endangered species rebound.

"It is difficult to watch monarch butterflies and their extraordinary migration teeter on the edge of collapse, but there are signs of hope," Anna Walker, a butterfly and moth expert at the New Mexico BioPark Society who led the IUCN's assessment, said in a statement.

She added that projects are underway to help protect monarch butterflies and their habitats.

"From planting native milkweed and reducing pesticide use to supporting the protection of overwintering sites and contributing to community science, we all have a role to play in making sure this iconic insect makes a full recovery," Walker said.