Over the last 30 million years, the Indian subcontinent has been pushing northwards into Eurasia. On the border between India and Tibet, the rocks have been raised 8 kilometers above sea level, creating the world's highest mountain range, the Himalayas. But to the east, the rocks have buckled into a series of steep north-south ridges cutting down through the heart of Yunnan, the parallel mountains of the Hengduan Shan.

 

These natural barriers serve to isolate Yunnan's plants and animals in each adjacent valley. While the huge temperature range between the snowy peaks and the warmer slopes below provides a vast array of conditions for life to thrive. Through spring, the Hengduan slopes stage one of China's greatest natural spectacles. The forests here are among the most diverse botanical areas in the world.

 

Over 18,000 plant species grow here, of which 3,000 are found nowhere else. Until little more than a century ago, this place was unknown outside China. But then news reached the West of a mysterious hidden world of the Orient: hidden among the mountains, a lost Shangri-la paradise. Western high society in the grip of a gardening craze was eager for exotic species from faraway places. This gave rise to a new breed of celebrity adventurers: intrepid botanist explorers, known as “the plant hunters”. Yunnan became their Holy Grail. The most famous was Joseph Rock, a real life Indiana Jones. Remarkable film footage captured his entourage on a series of expeditions as they pushed into the deepest corners of Yunnan.