Butterfly populations across the United States have experienced a troubling decline, shrinking by over a fifth within the last two decades. The study, which focused on the abundance of butterflies or the number of individuals within a specific area, revealed a grim picture for these delicate creatures. Between 2000 and 2020, butterfly numbers fell by 22%, with the US Southwest, one of the hottest and driest regions, seeing the most severe declines.
Some of the species most affected include the Florida white, Hermes copper, tailed orange, Mitchell's satyr, and West Virginia white. A staggering 33% of butterfly species have experienced significant declines, with certain species like Julia's Skipper losing more than 90% of their populations. In total, 107 species saw a decrease of more than 50% in their numbers. The once common West Coast lady butterfly has dwindled by 80%, highlighting that even familiar backyard species are not immune to these trends.
"That's alarming because it suggests even common butterflies aren't safe," said Prof Grames.
The research analyzed data from 12.6 million butterfly sightings, collected through 76,000 surveys across 35 monitoring programs. Citizen science initiatives, such as the North American Butterfly Association's Fourth of July counts, contributed significantly to this comprehensive study. The findings underscore the need for urgent conservation efforts to prevent further losses and prioritize species for protection under frameworks like the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and the Endangered Species Act.
"While the results aligned with global trends, seeing the extent of the decline at such a large spatial scale was sobering," Prof Eliza Grames remarked.
Despite the sobering news, there is hope for recovery. Butterflies have short generation times, allowing them to rebound quickly if conditions improve. Simple actions such as planting wildflowers, reducing pesticide use, or leaving portions of gardens unmowed can significantly enhance their survival prospects.
"Butterflies can recover quickly because they have short generation times. Small actions like planting wildflowers, reducing pesticide use, or even leaving part of a backyard unmowed can significantly improve their chances," Prof Grames explained.
The study highlights that drought conditions pose a dual threat to butterflies by directly impacting them and affecting their food and host plants.
"Drought is a double threat – it harms butterflies directly and also affects their food and host plants," added Prof Grames.
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