XINING, April 21 (Xinhua) -- Three smiling Tibetan children stand on a plateau in colorful blouses. Necklaces made of plastic bottles hang around their tiny necks. The plateau is about to turn green.

It is a picture taken in May 2017. In the picture, 9-year-old Tenzin is standing next to his two cousins in their hometown county of Zadoi in Yushu Tibetan Autonomous Prefecture in northwest China's Qinghai Province.

The prefecture is an important ecological barrier. Of the entire Sanjiangyuan National Park, 85 percent is located in Yushu. Sanjiangyuan is known as the headwaters of the Yangtze, Yellow and Lancang rivers. Tenzin's home county of Zadoi is the source of the Lancang River.

Tenzin said that when the picture was taken, he was running wild with his cousins on the grassland. They picked up plastic bags they saw and put them inside the empty bottles. Then they tied the bottles together with a rope and hung the bottles on themselves, just like a necklace.

"We were about to take the bottles to a local garbage recycling station," Tenzin said.

The environment in Yushu may have taken on a brand-new look, but back in the 1970s, due to climate change and over-herding, the area of grassland and forests in the Sanjiangyuan area decreased drastically. At that time, the grassland area nosedived by 1,389 square km, while the desert area increased by 674 square km. The entire area of wetlands and water also went down by 375 square km.

Beginning in 2005, China launched the country's biggest ecological project to protect and restore the environment in Sanjiangyuan. In 2016, China started piloting the Sanjiangyuan National Park.

Officials in Yushu also set up an ecological court in 2017 to deal with environment-related cases in the area. By the end of 2019, the court had handled 14 cases regarding environmental resources.

In recent years, the Sanjiangyuan National Park has enjoyed a better ecological environment, according to research results from the country's second comprehensive scientific expedition to the Qinghai-Tibet Plateau.

According to the research results, the pilot area of the Sanjiangyuan National Park and its adjacent areas have become warmer, wetter and greener, with stable vegetation productivity and a significant increase in the number of wild animals.

The productivity and quality of vegetation in the source of the three rivers have improved. Since 2012, the aboveground biomass of grassland in the pilot area of the park has continued to increase and stabilize.

In addition, satellite remote sensing has revealed that the number of Tibetan antelopes, Tibetan gazelles and Tibetan wild donkeys have reached 37,000, 34,000 and 17,000, respectively, within the 23,000 square km of the core conservation area in the pilot area of the park.

"In the past, areas more than 4,000 meters above sea level barely had any vegetation, and rubble was everywhere," said local forestry official Tashi. "Now there are plants wherever possible."

Local herdsmen have also transformed their roles.

In the park alone, for example, the government has employed 17,211 local ecological protectors, with each receiving 1,800 yuan (254 U.S. dollars) a month.

"We need to let everyone enjoy the ecological benefits," said Li Xiaonan, with the provincial department of forestry and grassland.