American butterflies disappear at the “catastrophic” rate

By Seth Borenstein, scientific writer AP

Washington (AP) – American butterflies disappear due to insecticides, climate change and loss of habitat, the number of winged beauties decreased by 22% since 2000, according to a new study.

The first systematic analysis at the scale of the country of the abundance of butterflies revealed that the number of butterflies in the 48 lower states has dropped on average 1.3% per year since the beginning of the century, with 114 species showing significant declines and only nine increases, according to a study of the journal Science of Thursday.

“Butterflies have decreased in the past 20 years,” said the study co-author, Nick Haddad, entomologist at Michigan State University. “And we see no sign that it will end.”

A team of scientists combined 76,957 surveys of 35 surveillance programs and mixed them for an apple comparison and ended up having 12.6 million butterflies during the decades. Last month, an annual survey that turned just on the monarch butterflies, which federal officials planned to put on the list of endangered species, had a low of less than 10,000 people, against 1.2 million in 1997.

Many decline species have dropped by 40% or more.

The loss of “catastrophic and sad” over time

David Wagner, an entomologist from the University of Connecticut who was not part of the study, praised his scope. And he said that if the annual decline rate may not seem significant, it is “catastrophic and sad” when aggravated over time.

“In just 30 or 40 years, we are talking about losing half of the butterflies (and other insects) on a continent!” Wagner said in an email. “The tree of life is bare to unprecedented rates.”

The United States has 650 species of butterflies, but 96 species were so sparse that it did not arise in the data and 212 other species were not found in a sufficient number to calculate trends, said Collin Edwards, a study of the study, an ecologist and scientist of the Washington Data Department of Fish and Wildlife.

“I am probably the most worried about species that could not even be included in the analyzes” because they were so rare, “said Karen Oberhauser of the University of Wisconsin-Madison, which was not part of the research.

Haddad, who specializes in rare butterflies, said in recent years, he had only seen two Satyr St. Francis butterflies disappearing – who live only on a range of Bragg’s Bragg bombs in North Carolina – “so he could be extinguished.”

Some well -known species had large drops. The red admiral, who is so calm that he lands on people, is down 44% and the American butterfly, with two large eyes on his rear wings, decreased by 58%, said Edwards.

Even the invasive white cabbage butterfly, “a species well suited to invade the world”, according to Haddad, dropped by 50%.

“How can it be?” Haddad wondered.

Billiards decline as a warning sign for humans

The butterfly expert at Cornell University, Anurag Agrawal, said that he was the most worried about the future of a different species: humans.

“The loss of butterflies, parrots and porpoises is undoubtedly a bad sign for us, the ecosystems we need and the nature we appreciate,” said Agrawal, who was not part of the study, in an email. “They tell us that the health of our continent is not doing so well … Butterflies are an ambassador for the beauty of nature, fragility and interdependence of species. They have something to teach us.

Oberhauser said that butterflies connect people to nature and that “calms us, makes us healthier and happier and promotes learning”.

What happens to butterflies in the United States probably arrives at other less studied insects through the continent and the world, Wagner said. He said that not only is it the most complete butterfly study, but the richest in data for any insect.

Butterflies are also pollinators, but not as prominent as bees, and are a major source of pollination of Cotton Harvest in Texas, said Haddad.

The driest and hottest areas are the worst for butterflies

The greatest decrease in butterflies has been in the southwest – Arizona, New Mexico, Texas and Oklahoma – where the number of butterflies has dropped more than half during the 20 years.

“It seems that butterflies that are in dry and hot areas are particularly bad,” said Edwards. “And this kind of capture a lot of southwest.”

Edwards said that when they looked at species of butterflies that lived both in the warmer and cooler south in the north, those who did better were in cooler areas.

Climate change, loss of habitat and insecticides tend to work together to weaken butterfly populations, said Edwards and Haddad. Of the three, it seems that insecticides are the largest cause, based on previous research from the US Midwest, said Haddad.

“It makes sense because the use of insecticides has changed dramatically over time since the start of our study,” said Haddad.

Habitats can be restored and butterflies too, so there is hope, said Haddad.

“You can make changes to your garden and in your neighborhood and your condition,” said Haddad. “It could really improve the situation of many species.”

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Originally published: March 6, 2025 at 11:08 a.m. PST