Research Finds California's Monarch Butterfly Population Dropped by 86 Percent Last Year

Image: AP

In what is yet another sad and alarming piece of news, the number of monarch butterflies in California has dropped precipitously and catastrophically in the past year.

The butterflies, which typically migrate to California from as far as Idaho and Utah in the winter, have been failing to make the commute. On Wednesday, the New York Times reported on the findings of a study conducted by the nonprofit group Xerces Society for Invertebrate Conservation which saw the population of monarch butterflies in California decline 86 percent from last year’s numbers. This is, if you can believe it, a historic low.

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This news is even more troubling when one considers that the total population of monarch butterflies has declined 97 percent since the 1980s. In 2017, a study conducted by the society posited that at this rate the entire North American monarch butterfly population had a 72 percent chance of becoming near extinct in 20 years.

In November, the sharp decline of monarch butterflies in the U.S. over the past two decades was referenced in the sweeping New York Times Magazine feature with a self-explanatory title, “The Insect Apocalypse Is Here”:

“In the United States, scientists recently found the population of monarch butterflies fell by 90 percent in the last 20 years, a loss of 900 million individuals; the rusty-patched bumblebee, which once lived in 28 states, dropped by 87 percent over the same period…. [A] whole insect world might be quietly going missing, a loss of abundance that could alter the planet in unknowable ways. ‘We notice the losses,’ says David Wagner, an entomologist at the University of Connecticut. ‘It’s the diminishment that we don’t see.’”

From the same piece, here’s a taste of what happens when insects, vital to decomposition and natural champions of harmonious ecosystems everywhere, disappear:

“When asked to imagine what would happen if insects were to disappear completely, scientists find words like chaos, collapse, Armageddon. Wagner, the University of Connecticut entomologist, describes a flowerless world with silent forests, a world of dung and old leaves and rotting carcasses accumulating in cities and roadsides, a world of ‘collapse or decay and erosion and loss that would spread through ecosystems’—spiraling from predators to plants.”

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The Times reported on Wednesday that monarch butterflies in particular are crucial because they pollinate flowers, and because their wellbeing is an indication of an entire ecosystems’s overall health.

Biologist Emma Pelton explained to the Times that monarchs thrive off milkweed, a plant that has undergone a recent decline due to pesticide use and urban development.

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About the author

Hannah Gold

contributing writer, nights