BBC: “Butterfly populations in the US shrank by more than a fifth within the space of two decades, according to a new study. Numbers fell by 22% between 2000 and 2020, according to research by Binghamton University in New York. A third of species saw serious decline, with some, like Julia’s Skipper, losing more than 90% of their populations. However, the researchers say butterflies may be able to recover if urgent conservation measures are taken. The study published in the journal Science measured butterfly “abundance” – the number of individuals of a species within a specific area. It analysed 12.6 million butterfly sightings from 76,000 surveys across 35 monitoring programmes. This included data from citizen science programmes like the North American Butterfly Association’s Fourth of July counts. Using statistical models, they estimated population trends for 342 species. The results showed that 33% were in significant decline, with many exhibiting extreme losses – 107 species declined by more than 50%…”

See also The New York Times – See How Butterflies Are Surviving, or Not, Near You. “Populations are falling in the United States, a new study has found. Look up what’s happening in your area. It’s hard to count insects. Even as scientists have found that many populations are in decline, they’ve struggled to understand the scale of what’s happening. Now, a groundbreaking new study offers the most comprehensive answers to date about the status of butterflies in the contiguous United States. In 20 years, the fleeting time it takes for a human baby to grow into a young adult, the country has lost 22 percent of its butterflies, researchers found.”