Sebastião Salgado is a photographer famous for mining the great upheavals of humanity: his 1990s project Migrations, for example, charted the mass movements of those in search of work from the countryside to the cities; in Workers, he documented industrial labour in 23 countries.
His latest project, Genesis, is different. Instead of observing men and women's struggles in a global, industrialised context, he sought out the natural world in what he calls its most "pristine" state, spending eight years on the road in 35 countries and in places as diverse as Siberia, Papua New Guinea, Alaska and the Democratic Republic of the Congo.
The result is a new book and exhibition which, after it opens to the public on Thursday at the Natural History Museum in London, will travel to Toronto, Rio, Rome and Paris.
From the flying foxes of Madagascar to Congolese lava flows; from a leopard sipping watchfully from a pool in Damaraland to the crags of Monument valley in Arizona, the exhibition presents a dizzying array of images of the natural world at its most dramatic, rendered in Salgado's trademark, deeply shadowed, black and white.
Alongside are photographs of those people who remain relatively isolated from the mainstream globalised world: the Nenets of Siberia, the rhythm of whose lives is intertwined with the reindeer they herd over the tundra into the Arctic Circle; and the Mursi and Surma women of Omo valley, south Ethiopia, some of the last people to wear lip-plates.
Salgado described how the project came about: during a bout of illness in the late 1990s, he returned to the ranch in Brazil where he grew up. He found it much changed: the lush vegetation and rich wildlife he remembered had withered and retreated.
With his wife and collaborator, Lélia Wanick Salgado, he decided to do something about it: they replanted nearly 2m trees and watched the landscape renew itself as birds and animals returned. The idea for Genesis was born: both paean to the natural world's capacity to renew itself and elegy for its loss.
The project demanded huge endurance from the photographer, who is a lean and stringy 69.
He travelled for about eight months of the year for eight years. "I walked for 47 days with 7,000 reindeer for the Nenets," he said. "For me, a Brazilian, in temperatures of -35C, -45C, spending 10 or 12 hours outside wasn't easy." His specialist clothing was discarded in favour of kit from the Nenets. "They said, 'Sebastião, you will not survive'."
Endurance was also required in Ethiopia. He added: "I walked 850km because there were no roads. It was an incredible trip, fabulous, but for me very tough – I was 65 years old." Modes of transport also included "boats, balloons and small planes".
The photographs are "a call to arms for us to preserve what we have. Of course it is not possible to ask people to go back to live in the forest, but we can preserve and protect this, our real heritage."
• Sebastião Salgado: Genesis is at the Natural History Museum, London, from 11 April to 8 September