Can one of the world’s great waterways survive its development?

GUO, the driver, pulls his car to a merciful halt high above a crevasse: time for a cigarette, and after seven hours of shuddering along narrow, twisting roads, time for his passengers to check that their fillings remain in place. Lighting up, he steps out of the car and dons a cloth cap and jacket: sunny, early-summer days are still brisk 3,500 metres above sea level. Mr Guo is an impish little dumpling of a man, bald, brown-toothed and jolly. He is also an anomaly: a Shanghainese in northern Yunnan who opted to stay with his local bride rather than return to his booming hometown.
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The ribbon of brown water cutting swiftly through the gorge below is rich with snowmelt. With few cars passing, its echoing sound fills the air. In the distance, the Hengduan mountains slump under their snowpack as if crumpled beneath its weight. Mr Guo recalls the drivers who have taken a switchback too quickly and fallen to their deaths in the valley below. He tells of workers who lost their footing or whose harnesses failed while building a bridge near his home town of Cizhong, 20 or 30 kilometres south. He pulls hard on his cigarette. “This river”, he says, “has taken so many lives.”

It has sustained many more. From trickles of meltwater in arid Qinghai, the river grows quickly as it passes through Tibet and Yunnan. Leaving China, and in doing so changing its name from the Lancang to the Mekong, it descends through a landscape ripening into jungle. Swollen by rainforest tributaries, it defines the Myanmar-Laos border and most of the Laos-Thailand border. It cuts Cambodia in two, and then splits into distributaries in south-western Vietnam, the lush, claustral delta landscape opposite in every way to the craggy austerity where it began.

The Mekong region is Asia’s rice bowl: in 2014 lower Mekong countries (Myanmar, Laos, Cambodia, Thailand and Vietnam) produced more than 100m tonnes of rice, around 15% of the world’s total. The region’s fertile soil depends on nutrient-rich sediment that the Mekong carries downriver, mainly during the rainy season from June to October; more than half the sediment in central Cambodia comes from China. The river and the nutrients it brings also support the world’s biggest inland fishery, accounting for a quarter of the global freshwater catch, feeding tens of millions of people.

The region boasts remarkable biodiversity; only the vast basins of the Congo and the Amazon compare to or surpass it. There are more than 20,000 types of plant and nearly 2,500 animal species; freshwater dolphins and giant catfish; spiders 30 centimetres across and, in a limestone cavern in Thailand, a day-glo pink, cyanide-secreting millipede. The human diversity is striking, too: Tibetan monks pray; Burmese traders buy and sell; Cambodian fishermen cast nets; Thai farmers reap; Vietnamese markets float. The history is as rich as the soil. The Buddha smiled while resting at the northern Lao city of Luang Prabang. Angkor Wat on the Mekong-fed Tonle Sap lake was among the biggest cities of the preindustrial world. The Khmer empire that built it dominated South-East Asia for longer than there have been Europeans in the Americas.

Since its French colonial days the Mekong has been more of a backwater. But the life-changing development seen elsewhere in Asia is spreading into this mostly rural world. Pickup trucks are replacing bullock-carts, karaoke bars dot lonely two-lane roads, fishermen can catch up on soap-operas at night. People are getting richer, and their lives longer.

And as modernity comes into the region, it also seeks to take something out. Countries see a new resource in the Mekong: not the support it offers rich networks of life, but the simple fact of its flow. The hydroelectric dams now built on and planned for the Mekong amount to one of the largest-ever interventions in a river’s course. As its currents are rechannelled down copper conduits to power far-off cities the river itself will be trapped behind a series of concrete walls. Its fisheries, agriculture and biodiversity will suffer; the lives lived on its banks will be reshaped with scant regard for the feelings of those who lead them

In teaching his students that change was the one true constant, the philosopher Heraclitus told them that no one ever steps in the same river twice. At the second step both man and river are not what they once were. In space and in time, from narrow gorges to salty seas and from great empires to impoverished peasantry, the river at Mr Guo’s feet encompasses more change than most. These new developments, though, feel like something more profound. Flow means change, but it also brings identity, because it embodies continuity. As the river is stilled, precious identities risk being lost for ever.