VOA慢速英語：科學(xué)家表示：益蟲逐步消失！
It is common to see many different kinds of insects while spending time outside in the summer. Some of these tiny creatures do not bother people and can even add beauty to the natural environment. Examples of these are insects like ladybugs, butterflies and fireflies.
Other insects can harm the environment or humans. Many are known to bite or sting. Some carry dangerous diseases. This group includes insects like mosquitoes, ticks and cockroaches. The population of these insects seems to stay large and healthy.
But scientists say this does not appear to be true for some flying insects that serve an important purpose. There is growing evidence that these insects are decreasing across the world.
Many of these insects are very important to plant growth and development. They also serve as a necessary link in the food chain and can help break down life when animals die.
One researcher looking into the current insect population is Doug Tallamy, a professor at the University of Delaware. He worries that a continual drop in the number of helpful insects could lead to disastrous results.
If the insects disappeared, Earth’s important life forms would begin to go away too, Tallamy told the Associated Press. This could result in a total breakdown of the ecosystem.
“How much worse can it get than that?” he asked.
Tallamy noted a statement by one of America’s best-known biologists, E.O. Wilson of Harvard University. Wilson once called insects “the little things that run the world.”
Wilson is now 89 years old. He told the AP that he remembers walking through Washington, D.C., in the past when it was “alive with insects, especially butterflies.”
Now, he said, “the flying insects are virtually gone.”
Wilson said this point seemed to be confirmed during a drive he made last year from Boston, Massachusetts, to the neighboring state of Vermont. He was surprised that, during his trip, he counted only one insect that had hit the car’s front window.
Several other scientists have carried out similar tests by checking how many insects hit their cars while traveling. An insect researcher from the University of Florida, Philip Koehler, reported that far fewer insects hit his vehicle today than in the past.
While researchers admit this method is not scientific, they say it can still help them understand the changing insect population.
Scientists say there are likely many reasons for the drop in flying insects. Most are related to the destruction of insect habitat caused by things like insecticides, other animals, pollution and climate change.
There have not been many studies done on the insect populations covering large areas. However, some international research suggests a downward turn.
In 2006, a group of studies estimated there had been a 14-percent drop in ladybugs in the United States and Canada from 1987 to 2006.
In Costa Rica, researchers have been studying the flying insect population at the La Selva Biological Station since 1991. One of the researchers is Lee Dyer from the University of Nevada, Reno. He told the AP his team has repeatedly examined a big trap that would have been covered with insects decades ago. Now, they find no insects in the trap.
In Germany, a 2017 study found an 82-percent drop in the number of flying insects captured in 63 traps across the country, compared to levels recorded in 1990. This is the main insect population study carried out so far.
Researchers say it is difficult making similar comparisons in other areas. That is because similar insect counts were not done decades ago.
After the German study, other countries also started looking into the problem. Toke Thomas Hoye of Aarhus University in Denmark studied flies in a few areas of rural Greenland. He said he discovered an 80-percent drop in the insects since 1996.
David Wagner of the University of Connecticut says other evidence leads him to believe the findings of the 2017 study are “clearly not a German thing.” Wagner has measured drops in moth populations in the northeastern United States.
“We just have to find out how widespread the phenomenon is,” he said.
I’m Bryan Lynn.
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Words in This Story
bother – v. annoy, worry or cause problems for someone
sting – v. produce a small but painful injury by making a small hole in the skin
ecosystem – n. all the plants, animals and people living in an area considered their environment
virtually – adv. almost
habitat – n. the natural surroundings in which a plant or animal usually lives
insecticide – n. chemical substance used to kill insects
phenomenon – n. someone or something considered special because it is completely different or extremely unusual
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