To protect the ecosystem, farmers living on the banks of the Yangtze River have begun to dramatically reduce the use of chemicals and adopt biological pest control methods.

Orange farmer Ran Xiaoli's orchard of navel oranges on the south bank of the river is a good example.

In addition to insect-trapping balls, solar-powered lamps and sticky cards, a special type of mite has been introduced to kill pests. One of the predatory mites, the size of a sesame seed, can eat an insect, such as a red spider, that's two or three times its size. A bag of 1,500 mites can kill all the pests on a citrus tree.

Ran, 37, is also director of Huolong, a community in Chongqing's Yunyang county. In 2005, she was the first in the area to plant orange trees and promote the idea of green agriculture.

Many fields had been abandoned, as young farmers left to work in the cities. Left-behind seniors grew traditional crops such as corn and rice. Some planted peach and plum trees.

"Different crops and fruit trees need different types of pesticides and fertilizer," Ran said. "The total amount of chemicals used by the farmers was huge, which severely damaged the soil and water."

After some research, she decided to try growing oranges using as few chemicals as possible. Her success encouraged people in the community. Now, about 80 percent of the residents have joined her.

"In the past, we spread pesticide five times a year," she said. "Now we use it only once or twice a year."

The world's third-longest river, the Yangtze stretches 6,300 kilometers from the glaciers of the Qinghai-Tibet Plateau eastward through Chongqing, Wuhan and Nanjing before reaching the East China Sea at Shanghai.

More than 400 million people get their drinking water from the Yangtze, and water security has become a major issue in China's development.

President Xi Jinping has attached great importance to restoring the river's ecology, and urged officials from provinces along the river to concentrate on restoration and protection, and to avoid large-scale development.

Chongqing, located in the upper reaches of the Yangtze, is among the 11 provinces and cities in the Yangtze River Economic Belt, a key national development strategy that has made ecological protection its most important mission.

Orange farming has become popular in Chongqing and the Three Gorges Reservoir area.

Wanzhou district in northeast Chongqing began building a national agricultural park to demonstrate the green agriculture concept in 2017.

"It can help reduce the use of pesticides and improve air quality," said Wang Xiaowei, who works in the fruit tree department of the Wanzhou Agricultural Commission. "Farmers also make more money from those organic products."