Butterfly numbers have fallen by nearly a quarter since 2000
ARI SHAPIRO, HOST:
Since the year 2000, the number of butterflies in the U.S. has dropped by nearly a quarter, according to a new study in the journal Science. As NPR's Jonathan Lambert reports, this decline of these fluttering bugs signals broader trouble for all kinds of insects.
JONATHAN LAMBERT, BYLINE: People love butterflies, says ecologist Collin Edwards.
COLLIN EDWARDS: They are pretty visually distinct, and you can identify them just by walking past them.
LAMBERT: That passion and ease of identification has sparked volunteers to spend hundreds of thousands of hours counting them.
EDWARDS: Frankly, the amount of volunteer effort in the U.S. in looking at butterflies gives us really one of the best insect data sets in the world.
LAMBERT: But no one had tried to combine all these patchwork efforts into a single analysis. So Edwards, currently at the Washington Department of Fish and Wildlife, and his colleagues sorted through millions of butterfly sightings from enthusiasts and professionals, to analyze how numbers have changed since the year 2000.
EDWARDS: We saw a decrease of about 22%. If you were seeing a hundred butterflies, you know, in the summer in 2000, on average across the country you'd be seeing 78 butterflies in the year 2020.
LAMBERT: That year-over-year decline worries David Wagner, a biologist at the University of Connecticut.
DAVID WAGNER: It doesn't sound like much, but 1- or 2% decline per year of any group is absolutely phenomenal when you compound that over more than one decade.
LAMBERT: Some butterfly species actually improved in numbers, especially those that thrive closer to humans. But such success stories were rare.
EDWARDS: We had 13 times as many species declining as we had increasing, and that was, frankly, a really rough number to see.
LAMBERT: And it was butterflies of all kinds, in every corner of the country. That generality suggests three major culprits - habitat loss, pesticide use and climate change. And those forces are likely impacting harder-to-study insects, too. That really worries Wagner.
WAGNER: Insects are the little things that run the world. They're pollinating, helping with our food. And so if butterflies are declining at 1.3% a year, we can bet that these 10 million other species that share our planet and make it run, make it function are in trouble, too.
LAMBERT: Wagner says addressing climate change and limiting pesticide use is key. And individuals can make a difference, too, with simple actions like planting butterfly-friendly plants in the backyard. Jonathan Lambert, NPR News.
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