At dusk, herdsman Dondrup drove some 100 sheep back to the flock. When he reached a stretch of sand, he stopped and scattered them. He hoped their dung could help the grass grow.
Dondrup's home is in Maqu County, Gannan Tibetan Autonomous Prefecture in northwest China's Gansu Province. The county sits on the upper reaches of the Yellow River, China's "mother river," which runs 5,464 km across the country from west to east before entering the Pacific.
Between Dondrup's family pasture and the river, there is a rolling sand belt that stretches some 100 meters. It used to be fertile grassland. Newly planted willows and sea buckthorn shoots reflect human attempts at controlling the sand.
The county has some 1.28 million hectares of grassland and 374,666 hectares of wetlands formed by the flow of meltwater from the Qinghai-Tibet Plateau.
Since the 1980s, the wetlands have shrunk and the sand has encroached on the prairie as a result of over-grazing, burrowing by rats, and wind erosion. This has raised fears that the "mother river" that has sustained China for thousands of years might someday dry up.
"When grandpa was young, there was not a single grain of sand in our pasture. My father has witnessed one-third of the pasture turn into sand. It is time for people of my generation to take some action," Dondrup said.
In order to turn things around, the county has turned to a combination of measures to fix the problem since 2013, such as introducing a grazing ban, combating rats, and increasing vegetation coverage.
In 2015, some 3,333 hectares of grass and about 90,000 trees were planted, and 4,180 hectares of wetlands were treated.
As grassland and wetlands are key to the livelihood of local herders, the environmental upgrading efforts unavoidably affect how they make a living.
"In order to help recover the grassland, I had to cut my cattle population from 500 to 200," Dondrup said. The government has been offering subsidies, but the amount is far from enough to cover the loss.
"But still, I think it's the right thing to do," he said, adding that the grass on his pasture has become much more lush since reducing his cattle.
Having witnessed the changes, more locals are joining the sand control army, and some are turning from livestock to tourism for a living.
Dondrup's neighbor, Zhoima Gyabug, sold all his cattle last year. He opened a Tibetan-style hostel and has been investing the money he makes from tourism into environmental control.
He planted 1,600 willow trees and has invested in treating over 12 hectares of grass in his own pasture for the past year.
"Tibetan people have an awe for nature. They have demonstrated great passion in environmental protection under the guidance of the government," said Lhamogya with the local animal husbandry, veterinary medicine and forestry bureau.
The provincial and prefecture governments have been working to beautify natural landscapes through garbage clean-up and building tourism facilities. Local people can also obtain financial support from the government to open hostels.
The central government initiated a flood control program on the Maqu section of the Yellow River in November 2015 in an effort to prevent the expansion of sand brought by the river.
To heal the fragile ecological system, local officials have called for more action.
The cattle population on the grassland still exceeds the ideal by some 50 percent, Lhamogya said.
"To further cut the cattle population, we need to maximize the value of the cattle by extending the industrial chain and developing the processing industry," he said. "We also have precious grassland mushrooms and medicine, which have yet to be developed."
Yang Changde, head of the agriculture and animal husbandry bureau of Gannan, said, "There are still no existing models for the treatment of desertified grassland and wetlands on the plateau. Hopefully scientists and experts will join us to offer some technological support."