Standing in a deep pit, the men are up to their knees in mud. They spray the walls with water from hoses, while one of them sucks up the loose material. A generator rattles.
A pump transports the water to the top, where it pours over a scaffolding that is covered with a carpet and forms a slide. Metre after metre, they hose down the muddy brown ground in the tropical heat, 12 hours a day, for one month.
Then they wash the carpet with a mercury solution. What remains is gold dust – and a trail of destruction left behind by illegal gold mining in the Amazon.
Wherever the "garimpeiros" cut aisles into the rainforest and dig deep into the earth, as in Creporizao in the west of the Brazilian state of Para, the forest recovers only with difficulty.
Researchers from the University of Leeds recently warned of the forests' problems with regrowth in the Journal of Applied Ecology.
"Tropical forests are severely affected by gold mining and mining," co-author Michelle Kalamandeen says,"and they hardly grow back on their own."
Kalamandeen and the other researchers warn that the consequences will persist for a long time – also with regard to climate change – and that active farming of the land is necessary.
The Amazonas region stores one of the biggest amounts of carbon dioxide worldwide. However, absorption and storage capacity decrease with the destruction of the rainforest.
According to the study, the tropical forests grow back particularly poorly in abandoned gold mining pits and quarries. The team conducted field research at two recently abandoned gold mines in Guyana, analysed soil samples and determined the biomass of individual trees.
In some places, the vegetation had hardly returned even long after gold mining had stopped.
The results indicate that nutrient depletion affects recovery more than mercury pollution. The rainforest's fertile soil layer is very thin. However, the high mercury content has serious implications for food security, water supply and biodiversity.
Today, there are over 20,000 garimpeiros scattered across their territory. The indigenous people, who consider themselves the "guardians of the forest," have started a campaign to expel the garimpeiros from their area between Brazil and Venezuela, which is the size of Portugal.
The illegal quest for gold in the north of South America, along the Guayana Shield, is responsible for 90% of deforestation in Guyana, Suriname, French-Guyana, Venezuela, Colombia and Brazil.
In the Brazilian Amazon, this quest is concentrated in the western region of Para with hundreds of illegal gold mining pits, with miners having long been in the territory of the indigenous Munduruku people.
The illegal search for gold in protected indigenous areas and national parks has increased overall. According to the environmental organisation Greenpeace, an area the size of 1,841 football pitches was deforested in indigenous areas and national parks for gold exploration in the first four months of 2020, compared to an area of 1,218 football pitches in the same period the year before.
There are places like Creporizao, resembling a village in a cowboy film, which doesn't have a post office or a bank, but there are a dozen shops that buy and sell gold, supplied by the garimpeiros.
They exchange it for money to spend in the city. The gold, in turn, travels into the world – via Sao Paulo to the US, Europe or Asia.
"This gold is the blood of the indigenous people," Kopenawa says. The Yanomani recently reported the murder of two indigenous people by illegal gold miners.
The incident recalls bad memories from the gold fever of the 1970s and '80s, when the garimpeiros killed 25% of the indigenous population, according to Kopenawa.
The coronavirus crisis has reawakened the desire for gold, as the metal is considered economically stable.
Critics accuse Brazilian President Jair Bolsonaro, who welcomes opening the Amazon region to economic activities, of encouraging gold diggers, and therefore fuelling deforestation.
Kalamandeen fears a race against time might make things even worse: "With a gold price of more than US$1,700 (RM7,091) an ounce (in July), estimated to reach US$3,000 (RM12,515) in the coming months, many gold diggers are already reacting quickly." – dpa