24th July 2022

Migratory monarch butterfly is now endangered

The migratory monarch butterfly, known for its spectacular annual journey of up to 4,000 kilometres across the Americas, is now classed by the IUCN Red List as endangered.

Credit: Joe Schelling

This week, the International Union for Conservation of Nature (IUCN) updated its Red List of Threatened Species. The migratory monarch butterfly, a subset of the monarch butterfly (Danaus plexippus) is now classed as endangered, due to habitat destruction and climate change.

Known for its winter migrations from Mexico and California to breeding grounds throughout the United States and Canada in summer, its population has seen an alarming decline over recent decades.

Logging and deforestation (both legal and illegal) to make space for agriculture and urban development has already destroyed substantial areas of the butterflies’ winter shelters in Mexico and California, while pesticides and herbicides used in intensive agriculture across the range kill butterflies and milkweed, the host plant that the larvae of the insects feed on.

Climate change has significantly impacted the migratory monarch butterfly and is a fast-growing threat; drought limits the growth of milkweed and increases the frequency of catastrophic wildfires, temperature extremes trigger earlier migrations before milkweed is available, while severe weather kills millions of butterflies.

Migratory routes. 1) March; 2) April; 3) End of April; 4) April – June; 5) June – August; 6) September – November
Credit: Harald Süpfle/B kimmel, CC BY-SA 3.0, via Wikimedia Commons

The western population is at greatest risk of extinction, having declined by 99.9%, from an estimated 10 million in the 1980s to just 1,914 now.

The eastern population is much larger but has seen major declines too, shrinking by 84% since 1996. Concern remains as to whether enough butterflies can survive to maintain the populations and prevent extinction.

Migratory monarch butterfly population size, 1993-2020. This graph includes the population totals across both eastern and western migratory populations.

“The Red List update highlights the fragility of nature’s wonders, such as the unique spectacle of monarch butterflies migrating across thousands of kilometres,” said Dr Bruno Oberle, IUCN Director General. “To preserve the rich diversity of nature we need effective, fairly governed protected and conserved areas – alongside decisive action to tackle climate change and restore ecosystems. In turn, conserving biodiversity supports communities by providing essential services such as food, water and sustainable jobs.”

“It is tragic to see one of the world’s most well-known butterfly species, with remarkable migratory behaviours and local cultural significance, threatened with extinction,” said Sophie Ledger, a researcher at the Zoological Society of London (ZSL) and member of the IUCN Butterfly and Moth Specialist Group. “Assessments like these provide us with the foundations for conservation actions to try and help protect a species and avert further loss. Here at ZSL, we are collaborating with global experts to shed light on the status of a wide range of species, including butterflies. Considering the current global biodiversity crisis, it is critical to uncover what is happening with diverse and functionally important species such as these before it’s too late.”

“It is difficult to watch monarch butterflies and their extraordinary migration teeter on the edge of collapse, but there are signs of hope,” said Anna Walker, member of the IUCN Butterfly and Moth Specialist Group and Species Survival Officer at New Mexico’s BioPark Society, who led the assessment. “So many people and organisations have come together to try and protect this butterfly and its 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.”

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