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For people in the cities, the simple beauty offered by a floating butterfly vanished long ago. In the valleys of Yunnan province in the southwest of China, explosions of brightly colored butterflies were a common spectacle. But even there, butterflies are now dying out.

A spectacular wonder. Every May, thousands of yellow butterflies are spotted¹ in the small valleys of Jinping county in southwest Yunnan province.

"This particular butterfly prefers humid climates. With 2500 millimeters of annual rain and vast vegetation, this area is an ideal breeding ground for the butterflies." Zhou Xuesong, ecological² expert with Southwestern Forestry³ University, said.

Expert says unique geographical⁴ conditions are also perfectly⁵ suited for the butterflies. The altitude of the valleys ranges from 130 to 3,000 meters, with tropic, subtropical and temperate⁶ zones. The forest coverage⁷ is over 70%. The area is filled with bamboo and flowers, and has few natural predators⁸ for the butterflies. But global warming and pollution have endangered the species, whose number has been dropping by a third every year.

"This massive breakout of butterflies has not been seen for three years. Their number is dropping dramatically. Say last year there were 10,000, this year it’s 3,000, and next year there would be only 1,000." Zhou said.

Experts say the extinction⁹ of insects is at the root of the problem. Sprawling¹⁰ cities leads to heavy pollution. The over-use of pesticides¹¹ and fertilizers also kills off these insects. If they go extinct, humans will be directly affected¹².

"85% of plants are host plants. When they bear fruits, they need these insects as a medium for fertilization. If they disappear, our agricultural production will be severely¹³ affected." Wu Xiaoqiang, associate professor with Southwestern Forestry University, said.

According to a global butterfly study by London Animal Society, the number of world butterflies is down by two thirds. If the trend is not reversed, some of the rare species could disappear forever.