When Davi Kopenawa Yanomami leaves home, you know the world is in trouble

When Davi Kopenawa Yanomami leaves home you know something's wrong. He's a shaman, or traditional healer, from one of the world's largest largest groups of isolated peoples. Home is Watoriki, a village in the northern Amazon, deep in the forests and mountains near the Brazilian border with Venezuela.

Davi leaves his orca, the great communal house where his village lives and sleeps, only to fight for his tribe. Twenty years ago, he came to London to alert the world to the plight of his people and the Brazilian rainforest.

More than 20,000 goldminers had invaded Yanomami tribal lands and as well as cutting down forests and poisoning the rivers, they brought violence and disease. With no immunity, one in five Yanomamai died within a few years from measles, malaria and other illnesses. Davi's uncle was murdered by the goldminers and the tribe faced extinction.

Davi was chosen to leave the village because he spoke Portuguese and had been in contact with white people, having worked with Funai, the Brazilian National Indian Foundation. He put on his toucan feathers, and accompanied by his shamanic spirtits, took boats and walked hundreds of miles first to Boa Vista and then to Manaus, the capital of Amazonas state.

The Brazilian politicians did not help, he said, and it was only when he was invited to Europe and then America in 1989 that the Yanomamai became an international cause, with rock stars like Sting putting the tribe on the map.

The international pressure worked. In 1992 the Brazilian government finally threw out the ranchers and goldminers from Yanomami land and demarcated an area the size of Portugal for the tribe.

But now Davi is back in London with a terrifying warning about threats from miners, cattle ranchers and climate change.

"History is repeating itself. Thousands of miners have come back," he told the Guardian in London this week. "They are repairing and expanding the old airstrips. The cattle ranchers are coming in, cutting down the forest. They are coming with planes and helicopters, guns and machines and rafts. They bring malaria and destroy the rivers. We are warning the world that without your help the Yanomami people will die.

"The error of the whites is to take the riches of the land. You only want to take the riches. But the land is sacred. If the Yanomamai die the shamans will disappear and the governments will continue to take the land. You are worried about climate change. It is arriving. The rains come late, the sun behaves in a strange way. The world is ill. The lungs of the sky are polluted. We know it is happening.

"We are shamans. We care for the planet, the sun, the moon the darkness and the light. Everything that exists we look after. You cannnot go on destroying nature. We will all die, burned and drowned, and that is the Yanomamai word."