The alarming disappearance of butterflies in the United States is rooted in the effects of insecticides, climate change, and habitat degradation, according to new research.
Since the year 2000, the population of these vibrant insects has decreased by 22%.
A thorough analysis featured in the journal Science reveals that, on average, butterfly numbers across the continental U.S. have diminished by 1.3% annually.
The study examined butterfly abundance from 114 declining species, while only nine species showed an increase.
Entomologist Nick Haddad, who co-authored the study, highlighted this troubling downward trend.
“The dwindling numbers of butterflies we’ve observed over the past two decades show no signs of improving,” said Haddad, a Michigan State University expert.
Researchers collaborated on 76,957 surveys from 35 different monitoring initiatives, encompassing over 12 million butterflies through the decades.
Moreover, a recently conducted annual counting effort on monarch butterflies recorded a substantial drop to an all-time low of fewer than 10,000, plummeting from 1.2 million in 1997.
Several species have experienced declines of 40% or more.
University of Connecticut entomologist David Wagner, unaffiliated with the study, lauded its comprehensive scope.
He emphasized that while a 1.3% annual reduction might seem inconsequential, the cumulative effect over years is severe and disheartening.
“Within the next 30 to 40 years, we’re looking at potentially losing half the butterfly population and other insect species throughout the continent,” Wagner noted, warning about the potential for a “denuded” ecosystem.
With the U.S. home to 650 butterfly species, there are concerns for the 96 species too rare for inclusion in the analysis, along with another 212 species showing insufficient numbers for identifying trends, according to lead author Collin Edwards from Washington’s Department of Fish and Wildlife.
University of Wisconsin-Madison entomologist Karen Oberhauser, not involved in the study, voiced similar worries, particularly regarding the unaccounted species.
Haddad, whose expertise lies in rare butterflies, recounted spotting only two endangered St. Francis Satyr butterflies recently, suggesting a potential near-extinction.
Among noted declines, the red admiral and American lady butterflies registered reductions of 44% and 58% respectively, while the invasive white cabbage butterfly also saw a surprising 50% decrease.
Anurag Agrawal from Cornell University stressed the significance of these findings, linking them to broader ecological implications for humans.
Stressing the importance of these trends, Agrawal pointed out how butterfly losses indicate troubling conditions for human well-being and ecosystem balance.
Butterflies symbolize the interconnectedness and delicate nature of ecosystems.
Oberhauser highlighted the intrinsic connection between humans and nature, which butterflies enhance by fostering stress relief, health benefits, and learning.
This nationwide scenario appears indicative of global insect population declines, echoed Wagner.
This study sets a benchmark, being among the most comprehensive data-driven research on insects.
Butterflies serve vital ecological roles such as pollination, particularly aiding crops like Texas cotton, added Haddad.
The Southwest region faced the sharpest decline, losing over half its butterfly population.
“Butterflies in hotter, arid regions are the hardest hit,” noted Edwards, linking warmer climates with these decreases.
Species thriving are often in cooler zones.
Researchers suggested insecticides, habitat loss, and climate change collectively threaten butterfly populations, singling out insecticides as the primary culprit.
According to Haddad, drastic changes in insecticide use since the start of their study have exacerbated these issues.
However, hope lies in habitat restoration opportunities.
Haddad encouraged grassroots actions like improving gardens and local areas to bolster species survival.
