Why monarch butterflies, now endangered, are on the ‘edge of collapse’

The migratory monarch butterfly, a North American icon with a continent-spanning annual journey, now faces the threat of extinction.

Thursday’s decision by the International Union for Conservation of Nature to declare the species endangered comes as years of habitat destruction and rising temperatures have decimated the fluttering orange itinerants’ population.

The species’ numbers have dropped between 22 and 72% over the past decade, according to the new assessment. Monarchs in the Western United States are in particular danger: The population declined by an estimated 99.9%, from as many as 10 million butterflies in the 1980s to fewer than 2,000 in 2021.

Despite being able to survive thousands of miles of migration, the monarch now faces abundant threats from humans.

Forest-clearing to harvest timber and to make space for farms and homes is creeping into its wintering grounds. Pesticides and herbicides threaten not only the insect itself but also milkweed, which monarch larvae need to live.

Among butterflies, the monarch is not alone. Butterflies across the West are vanishing as the region gets hotter and drier. According to one recent study, a majority of 450 species across a swath of 11 Western states are dropping in numbers.

The loss of monarchs underscores a looming extinction crisis worldwide, with profound implications for the humans who have caused it. One million species could disappear, according to the United Nations, a potential calamity not just for plants and animals but also for the people who depend on ecosystems for food and fresh water.

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