Scientists fear nonpest insects are declining
OXFORD, Pa. — A staple of summer — swarms of bugs — seems to be a thing of the past. And that’s got scientists worried.
Pesky mosquitoes, disease-carrying ticks, crop-munching aphids and cockroaches are doing just fine. But the more beneficial flying insects of summer — native bees, moths, butterflies, ladybugs, lovebugs, mayflies and fireflies — appear to be less abundant.
Scientists think something is amiss, but they can’t be certain: In the past, they didn’t systematically count the population of flying insects, so they can’t make a proper comparison to today. Nevertheless, they’re pretty sure across the globe there are fewer insects that are crucial to as much as 80 percent of what we eat.
“You have total ecosystem collapse if you lose your insects. How much worse can it get than that?” said University of Delaware entomologist Doug Tallamy. If they disappeared, “the world would start to rot.”
He noted Harvard biologist E.O. Wilson once called bugs: “The little things that run the world.”
It hit home last year when the 89-yerold Wilson drove from suburban Boston to Vermont and decided to count how many bugs hit his windshield. The result: a single moth.
Windshield test
The unscientific experiment is called
the windshield test. Wilson recommends everyday people do it themselves to see.
Research has shown dwindling individual species in specific places, including lightning bugs, moths and bumblebees. One study estimated a 14 percent decline in ladybugs in the United States and Canada from 1987 to 2006.
The evidence
Last year, a study that found an 82 percent midsummer decline in the number and weight of bugs captured in traps in 63 nature preserves in Germany compared with 27 years earlier. It was one of the few, if only, broad studies. Scientists say similar comparisons can’t be done elsewhere because similar bug counts weren’t done decades ago.
“We don’t know how much we’re losing if we don’t know how much we have,” said University of Hawaii entomologist Helen Spafford.
After the German study, countries started asking if they have similar problems, said ecologist Toke Thomas Hoye of Aarhus University in Denmark. He studied flies in a few spots in remote Greenland and noticed an 80 percent drop in numbers since 1996.
“It’s clearly not a German thing,” said University of Connecticut entomologist David Wagner, who has chronicled declines in moth populations in the northeastern United States.
The suspects
Most scientists say lots of factors, not just one, caused the apparent decline in flying insects. Suspects include habitat loss, insecticide use, the killing of native weeds, single-crop agriculture, invasive species, light pollution, highway traffic and climate change.
“It’s death by a thousand cuts, and that’s really bad news,” Wagner said.
To Tallamy, two causes stand out: Humans’ war on weeds and vast farmland planted with the same few crops.
Weeds and native plants are what bugs eat and where they live, Tallamy said.
Milkweeds, crucial to the beautiful monarch butterfly, are dwindling fast. Manicured lawns in the United States are so prevalent that, added together, they are as big as New England, he said. Those landscapes are “essentially dead zones,” he said.
Light pollution is another big problem for species such as moths and fireflies, bug experts said. Insects are attracted to brightness, where they become easy prey and expend energy they should be using to get food, Tallamy said.
Jesse Barber of Boise State is in the middle of a study of fireflies and other insects at Grand Teton National Park. He said he notices a distinct connection between light pollution and dwindling populations.
“We’re hitting insects during the day, we’re hitting them at night,” Tallamy said.
Restoring habitat
Governments are trying to improve the situation. Maryland is in a three-year experiment to see if planting bee-friendly native wildflowers helps. University of Maryland entomology researcher Lisa Kuder says the usual close-crop “turf is basically like a desert” that doesn’t attract flying insects. She found an improvement — 70 different species and records for bees — in the areas where flowers are allowed to grow wild and natural alongside roads.
The trouble is that it is so close to roadways that Tallamy fears that the plants become “ecological traps where you’re drawing insects in and they’re all squashed by cars.”