From Madoi County, a settlement near the headwater of the Yellow River, our two-car convoy headed out to visit a desert Yang Yong first viewed through binoculars in 1997. At the time, the geologist had seen a small, wind-blown patch of sand surrounded by greenery. This time, Yang looked out past a stretch of sloping grassland to where a new desert extended beyond the horizon. That sandy expanse, Yang told me, was where we would spend the night.

Yang, now sixty, is one of China’s most prominent environmentalists. For nearly thirty years, he has studied environmental changes in the Tibetan plateau, in particular the region where the Yellow, Yangtze, and Mekong Rivers originate. Using satellite images, remote sensing, and data collected on expeditions, he and his crew are documenting the degradation of lands along the headwaters of China’s major rivers. In May 2018, I joined Yang on an expedition to capture the transformation of the Yellow River and its surrounding landscapes.

We piled into our cars and drove off the road, with Yang’s yellow SUV leading the way through the grasslands and down the side of a hill. With no obvious route, the uneven ground caused the car to jolt so violently that some of our heads hit the roof.

Partway, Yang stopped the car and got out. It looked like he had changed his mind about driving any farther. He lit a cigarette, taking long drags as he contemplated the rough terrain ahead.

Shortly afterward, Yang got back in the car and told us to buckle up. With a series of deft manoeuvres, he slalomed down the hill, twisting the vehicle like an Olympic skier. I thought that, when we reached the sand, the rest would be easy. But, almost as soon as we did, our tires spun freely. We got stuck.

There are many forces causing desertification on the plateau, including natural physical processes, human mismanagement, and climate change. The land, which ranges from semiarid to arid, is unable to sustain high densities of human and wildlife populations, while the high altitude and dry climate can make it vulnerable to wind erosion. Rising temperatures accelerate the melting of permafrost, exposing once-frozen topsoil to winds and burrowing rodents. Some claim that overgrazing has contributed to the damage. The Tibetan plateau’s water cycle is also under severe stress, with shrinking glaciers, expanding lakes, and overflowing rivers in some parts.

Yang hopes his research will help officials protect the Sanjiangyuan, a nature reserve established in 2000 to protect the headwaters of the Yangtze, Mekong, and Yellow Rivers. He is careful not to criticize government officials for their mismanagement of natural resources; instead he shares his findings with them. By involving them in his work, he tries to influence rather than challenge them. To Yang, when it comes to the environment, diplomacy is far more effective than shame.

The Sanjianguyan National Nature Reserve, with the Yellow River running through it.
The Sanjiangyuan National Nature Reserve was created in 2000, when it became clear that the Yellow River was drying up: in 1997, the river failed to reach the sea for nearly eight months. Despite efforts to sustain the river, industry, agriculture, and urbanization continue to take a toll. Click on image to expand
A panoramic photo of yaks grazing around a lake in the Sanjiagyuan.
Yaks graze around a lake in the Sanjiangyuan. Experts disagree about whether grazing herds are exacerbating the desertification of grasslands—some believe that human activity, such as gold mining in the outer regions of the reserve, bears more responsibility. Click on image to expand
A woman stands between two men, wearing jackets and hats and standing in darkness as they consult a map.
Yang Yong (right); his wife, Wang Qiang, who handles the research team’s finances; and drone operator and logistics coordinator “Captain” Lu—an old friend of Yang’s—plan the next stages of their expedition.
Several people push on the hood of a yellow truck to try and dislodge it from sand as a woman looks on.
Yang’s expedition group, the Hengduan Mountain Research Society, includes his brother Yang Hongbing—the crew’s unofficial chef—and his apprentice Xiao Wei, who records Yang Yong’s scientific observations. Their fieldwork can require physical labour.
Dozens of sheep graze in the boundary between desert and grassland.
Sheep graze at the boundary between desert and grassland.
A wide-angle view of the Yellow River's Liujiaxia dam.
The Yellow River’s Liujiaxia dam, built in the late 1960s, generates electricity and is used to control flooding and irrigation. China has more than 87,000 dams—more than any other country. Around 23 million people have been displaced from their homes for such projects. Click on image to expand
A panoramic shot of the town of Guide, which contains lush vegetation and is backed by huge mountains.
The lush vegetation in the agricultural town of Guide is fed by upstream reservoirs. Farther downstream, the river turns its characteristic yellow, a sign of high silt content, which wears down the river’s many short-lived dams. Click on image to expand
A distant shot of hillsides in northwestern China, which are covered with new saplings.
Saplings take root on a hillside, where they’ve been planted as part of a government program known as the Green Great Wall, an initiative aimed at slowing desertification in northwestern China. Click on image to expand
A wide view of the city of Lanzhou, which is very industrial with a hazy sky.
Lanzhou, the last stop on my journey along the Yellow River, is also one of China’s oldest cities. Today, it is a major petrochemical hub. Click on image to expand

This story was produced with support from the Pulitzer Center

Ian Teh
Ian Teh is a Kuala Lumpur-based photographer. His work has appeared in National Geographic, The New Yorker, and Mother Jones.