[Photo by Jun Cheng/provided to China Daily]

"European mining companies are moving in. New roads are being built," he says.

"How can the caravans last if it takes a camel a week and an automobile three hours to transport salt?"

Jun Cheng believes it's crucial to return to the same locations to capture changes.

Transformations are especially conspicuous when photographing nature. A volcano that has been active for a century may be dormant later.

Not everyone can endure such journeys.

Jun Cheng recalls one team member quit when they were approaching the airport.