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In this archive photo from May 26, 2010, a Coccinellidae, more commonly known as ladybug or ladybird, rests on the petals of a rose in Portland, Oregon. One study estimates 14% ladybug numbers in the United States and Canada from 1987 to 2006. (AP Photo / Don Ryan)
A summer food – swarms of insects – seems to be a thing of the past. And scientists are worried.
Heavy mosquitoes, ticks with diseases, aphids and cockroaches are doing very well. But the most beneficial flying insects of the summer – native bees, moths, butterflies, ladybugs, bugs, mayflies and fireflies – seem to be less abundant.
Scientists think that something is wrong, but they can not be certain: in the past, they did not systematically count the population of flying insects, so they can not make any comparison with the current population. Nevertheless, it is certain that globally, there are fewer insects essential to 80% of our diet.
Yes, some insects are parasites. But they also pollinate plants, are a key link in the food chain and help break down life.
"You have a total ecosystem that collapses if you lose your insects – how bad can it be?" said entomologist at the University of Delaware, Doug Tallamy. If they are gone, "the world would start to rot".
He noted Harvard biologist E.O. Wilson once called insects "the little things that make the world go round".
Wilson, 89, recalled that he had once frolicking in a "living Washington of insects, especially butterflies". Now, "flying insects are practically gone".
Last year, he returned home from the suburbs of Boston to Vermont and decided to count the number of bugs hitting his windshield. The result: a single butterfly.
WINDSHIELD TEST
The non-scientific experience is called the windshield test. Wilson recommends that ordinary people do it themselves. Baby boomers will probably notice the difference, Tallamy said.
Several scientists have done their own tests with windshields, grilles and car headlights, and most of them have noticed some crushed insects. Researchers are quick to point out that such exercises are not good scientific experiments because they do not include control groups or allow comparisons with previous results. (Today's cars are also more aerodynamic, so bugs are more likely to overtake them and live on it.)
Yet there are signs of decline. Research has shown that individual species are declining in specific places, including insects, moths and bumblebees. One study estimated a 14% decrease in ladybirds in the United States and Canada from 1987 to 2006. The University of Florida's urban entomologist, Philip Koehler, has seen a recent decrease in insects – this year, a- he said, "it was rather disappointing, I thought."
The University of Nevada, Reno, researcher Lee Dyer and his colleagues have been studying insects at the La Selva Biological Station in Costa Rica since 1991. Several decades ago, a large insect trap with black light would be covered d & # 39; insects. Now, "there are no insects on this sheet," he said.
But there is not much research on all flying insects in large areas.
THE PROOF
Last year, one study found an 82% decrease in the number and weight of insects caught in the traps of 63 nature reserves in Germany in the middle of the summer compared to 27 years ago. It was one of the few, if only, broad studies. Scientists say similar comparisons can not be made elsewhere because similar bug counts have not been done decades ago.
"We do not know how much we lose if we do not know how much we have," said entomologist Helen Spafford of the University of Hawaii.
The absence of older data does not help to know how far we are facing arthropocalypse, said May Berenbaum, an entomologist at the University of Illinois. Individual studies are not convincing in themselves, "but the accumulated weight of evidence seems to be changing," she said.
After the German study, countries began to ask if they had similar problems, said ecologist Toke Thomas Hoye of the Aarhus University in Denmark. He has studied flies in some parts of Greenland and has seen a decline of 80% since 1996.
"This is clearly not a German thing," said David Wagner, an entomologist at the University of Connecticut, who recounted the decline of moth populations in the northeastern United States. "We just need to know how widespread the phenomenon is."
THE SUSPECTS
In this archive photo from June 27, 2017, ephemera swarm around the lights of a baseball stadium during a baseball game in Cincinnati. Experts say that light pollution is a big problem for some species of insects. Some insects are attracted to the light, where they become easy prey and spend energy they should use to feed themselves, said University of Delaware entomologist Doug Tallamy. (AP Photo / John Minchillo)
Most scientists say that many factors, not one, have caused the apparent decline of flying insects.
The suspects include habitat loss, the use of insecticides, the destruction of native weeds, monoculture, invasive species, light pollution, road traffic and climate change.
"It's death by a thousand denominations, and that's really bad news," Wagner said.
For Tallamy, two causes stand out: the war of humans against weeds and the vast farmland planted with the same few crops.
Weeds and native plants are what insects eat and where they live, Tallamy said. Milkweeds, crucial for the beautiful monarch butterfly, are rapidly declining. The well-manicured lawns in the United States are so widespread that, they add, they are as big as New England, he said.
These landscapes are "essentially dead zones", he said.
Light pollution is another big problem for species such as moths and fireflies, experts said. Insects are attracted to brightness, where they become easy prey and expend energy that they should use to feed themselves, Tallamy said.
Jesse Barber of Boise State is studying fireflies and other insects in Grand Teton National Park. He said that he notices a distinct link between light pollution and dwindling populations.
"We hit insects during the day, we hit them at night," Tallamy said. "We hit them pretty much everywhere."
Lawns, light pollution and road traffic caused by the massacres are associated with people who gather. But the Danish scientist Hoye found a noticeable drop in musk flies in Greenland, 500 kilometers from civilization. His studies linked declines to higher temperatures.
Other scientists claim that climate change of human origin could play a role, even minimal.
RESTORE THE HABITAT
Governments are trying to improve the situation. Maryland is in a three-year experiment to see if the native wildflower plantation helps bees.
Lisa Kuder, an entomology researcher at the University of Maryland, says "turf is like a desert" that does not attract flying insects. She has found an improvement – 70 different species and registers for bees – in areas where flowers are allowed to grow wild and natural along the roads.
The problem is that Tallamy is so close to roads that plants become "ecological traps in which you attract insects and are crushed by cars".
Tallamy remains optimistic. In 2000, he moved to this rural area between Philadelphia and Baltimore and turned his 10-acre parcel into native plants, creating a playground for insects. It now has 861 species of butterflies and 54 species of breeding birds that feed on insects.
Wagner, from the University of Connecticut, spends his summers teaching college students in a camp to look for insects, as he did decades ago. They have trouble finding the cocoons he saw regularly.
"The kids I'm teaching right now are going to think that rare insects are the rule," said Wagner. "They do not realize that there could be an ecological disaster on the horizon."
Explore more:
Insects in the face of climate change
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