In a sign of the sensitivity of the subject, the authorities declined to officially answer the Guardian's questions. Privately, officials said resettlement and other efforts to restore the grassland, including fencing off the worst areas, were worthwhile.

"The situation has improved slightly in the past five years. We are working on seven areas, planting trees and trying to restore the ecosystem around closed gold mines," said one environmental officer. The problem would not be solved in the short term. "This area is particularly fragile. Once the grasslands are destroyed, they rarely come back. It is very difficult to grow grass at high altitude."

The programme's effectiveness is questioned by others, including Wang Yongchen, founder of the Green Earth Volunteers NGO and a regular visitor to the plateau for 10 years. "Overgrazing was considered a possible cause of the grassland degradation, but things haven't improved since the herds were enclosed and the nomads moved. I think climate change and mining have had a bigger impact."

Assessing the programme is complicated by political tensions. In the past year, three prominent Tibetan environmental campaigners have been arrested after exposing corruption and flaws in wildlife conservation on the plateau.

Infestation

Another activist, who declined to give his name, said it was difficult to comment. "The situation is complicated. Some areas of grassland are getting better. Others are worse. There are so many factors involved."

A growing population of pika, gerbils, mice and other rodents is also blamed for degradation of the land because they burrow into the soil and eat grass roots.

Zoologists say this highlights how ecosystems can quickly move out of balance. Rodent numbers have increased dramatically in 10 years because their natural predators – hawks, eagles and leopards – have been hunted close to extinction. Belatedly, the authorities are trying to protect wildlife and attract birds of prey by erecting steel vantage points to replace felled trees.

There is widespread agreement that this climatically important region needs more study.

"People have not paid enough attention to the Tibetan plateau. They call it the Third Pole but actually it is more important than the Arctic or Antarctic because it is closer to human communities. This area needs a great deal more research," said Yang Yong, a Chinese explorer and environmental activist. "The changes to glaciers and grasslands are very fast. The desertification of the grassland is a very evident phenomenon on the plateau. It's a reaction by a sensitive ecosystem that will precede similar reactions elsewhere."

Phuntsok Dorje is unlikely to take part in any study. But he's seen enough to be pessimistic about the future. "The weather is changing. It used to rain a lot in the summer and snow in the winter. There was a strong contrast between the seasons, but not now. It's getting drier year after year. If it carries on like this I have no idea what I will do."

Additional reporting by Cui Zheng

Photo: Antoine Taveneaux

(Republished with permission)