U.S. butterflies 'all in trouble' as their numbers rapidly decline: Report
Over the past 20 years the U.S. butterfly population has declined 22%, a dramatic loss that has scientists concerned.
"The easy number to think about is the total number of butterflies in your yard. If you had a garden in 2000 and you saw 100 butterflies, you'd see only about 78 in the year 2020," said Collin Edwards, an ecological modeler with the Washington state Department of Fish and Wildlife and first author on the paper being published in the journal Science.
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Researchers across the United States collected data on more than 35 butterfly monitoring programs. It included data from 12.6 million individual butterflies comprising 554 species taken in 756,957 surveys.
The results were worse than researchers expected.
"It would be really nice to be able to say that this one group of butterflies is in trouble but everywhere else is fine. But no. They are all in trouble, everywhere," Edwards said.
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The chief causes of the decline include habitat destruction, drier and hotter climate because of climate change and insecticide use.
Butterflies have been declining for a long time, but the scientists began in 2000 because most butterfly monitoring programs didn't exist before that. They stopped in 2020 because many of those programs shut down during COVID, which could have skewed their data.
While butterflies might just seem like pretty insects that make children smile and add color and beauty to gardens, they're important for two reasons.
The first is that butterflies are important in nature. "It's easy to forget that the flapping around pretty part is just one portion of their lifecycle," said Edwards. "The eggs, pupae and caterpillars are in your garden year-round, and a lot of birds rely on them for food."
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Any decrease in butterflies also means other insects, ones that aren't as charismatic or easy to spot, are also decreasing.
Threatened insects
We have more data on butterflies because they're so easy to count.
"They're really easy to identify on the wing," Edwards said. "I've done wasp studies where you have to catch them and take them back to the laboratory to look at them under a microscope to identify them."
Insects are tiny, but they play a critical role in the ecosystems we depend on and they, too, are in trouble.
A meta-analysis of 16 scientific studies done in 2021 found that insect populations globally have declined by about 45% in just the past 40 years. It's one of the reasons your windshield is less covered in bug splatter than in your grandparents' time.
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This large-scale decrease in the number of insects in the world is a threat not just to ecosystems but also agriculture.
According to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, insects pollinate about 75% of global crops and as much as $577 billion in global food production relies on them.
That's not to say that butterflies aren't also important for farmers. One study found that butterflies and flies contribute as much as $120 million a year to cotton producers in Texas.
How you can help butterflies
While home gardeners can't fix widespread habitat loss or global warming, it is possible to make a haven for butterflies in your yard.
Even a small space can make a big difference for local species, said Edwards. "Local changes to improve habitats for butterflies also help buttress them against the effects of climate change."
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According to researchers at Tufts University, this can include simple changes such as:
Planting native plants that will provide food for your local butterfly species.
Minimizing insecticide use.
Growing a diverse group of plants to provide nesting habitats and allowing some ground to remain bare.
Letting at least some of your lawn grow into a more meadow-like area.
Some good news about butterflies
The good news is that butterflies can rebound quickly, when given appropriate habitat.
"A lot of endangered species, like killer whales or elephants, are long-lived and only have one offspring at a time, so it takes a long time for the population to grow," Edwards said. "But butterflies can lay hundreds of eggs and have two or three generations a year. So if you make it possible for not just one or two to survive but hundreds, they can rebound quickly."
This article originally appeared on USA TODAY: US butterflies 'all in trouble' as their numbers rapidly decline, report finds.
Reporting by Elizabeth Weise, USA TODAY / USA TODAY.
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