Can you imagine a world without insects? Without ants or flies in your house, it might sound great. However, the results may be out of imagination. 

The number of insects has dropped by half in the past few years, according to a British biologist Dave Coulson. You may think small insects are not important. But in fact they are the main part of the species(物种)on Earth. 

Insects are indeed on the way to extinction, according to the first review of insect population. The researchers say the main reason for this is the use of pesticides(杀虫剂)because they destroy insects' living areas. Also, weather change is another important cause.

"Unless we change our ways of producing food, insects will go down the way to extinction in a few years," the researchers wrote in the review. "This will have huge influences on the planet's ecosystem(生态系统)."

We need insects to pollinate(授粉)crops. They also break down(分解)dead plants and animals, which can keep the soil healthy. Without insects, many animals would have nothing to eat and die of hunger. Then, the ecosystem would be off balance. 

"If the number of insect species keep dropping, this will have bad influences on both Earth's ecosystem and the survival of us humans," said one of the writers of the review.

"The first step to stop this is to let more people understand the values of the natural world," he suggests. "The best place to start is from our children, who should realize environmental protection from an early age."