SÃO FÉLIX DO XINGU – As João Inácio de Assunção’s small boat sliced through the clay-colored waters of Rio Fresco in northern Brazil, he recalled a different time when the river was clearer and brimming with fish.

“There used to be so many types of fish here,” said 51-year-old de Assunção as he steered the engine-powered boat. “Things have changed a lot.”

De Assunção has spent 30 years working on the river, which cuts through São Félix do Xingu, a municipality in the northern state of Pará better known for its frenzied cattle production. Yet in recent years, it has become increasingly difficult for fishermen like him to survive from the river.

“Now the fish are dying, they are disappearing,” he said.

Environmentalists point to a surge in illegal gold mining in this corner of the Brazilian Amazon, which has brought along with it a dramatic rise in water pollution and deforestation, as speculators clear swaths of forest along the riverbanks to make way for makeshift mines known as garimpos.

This activity has done “irreversible damage” to the rivers in the region, said Gilberto Santos, who works with the Comissão Pastoral da Terra (CPT) in São Félix do Xingu, an arm of the Catholic Church that strives to advance human rights in rural communities in Brazil.

“There’s always been mining speculation here – but in recent years, it has spread like a fever, ” said Santos. “And the water they are polluting is in small rivers and streams that flow directly into Rio Fresco.”

Local sources say the most dramatic pollution has occurred in Rio Branco, a narrow river that snakes through the adjacent region of Ourilândia do Norte – or Northern Land of Gold – before flowing into the larger Rio Fresco.

The Ourilândia do Norte municipality, most of which was still covered in lush forest a few years ago, has recently seen a sharp rise in clearing: it lost more than 5 percent of its forest cover between 2001 and 2018, according to satellite data from the University of Maryland (UMD). About half of this loss occurred in 2017 and 2018 alone, indicating deforestation in the region may be accelerating.

And there are also signs that this acceleration has kept up this year: preliminary data from UMD indicate deforestation spiked in September and October to more than double the average rate for the same period over the past four years. Satellite images show the bulk of 2019 deforestation is due to mining expansion, much of it clustered around Rio Branco.

Local sources say some illegal miners – known as garimpeiros – dump toxic waste directly into the river. But most of the pollution occurs because the removal of forest and topsoil has badly weakened the banks of Rio Branco, said Daniel Clemente Vieira Rêgo da Silva, adjunct professor at the Federal University of Southern and Southeastern Pará (Unifesspa) in São Félix do Xingu. This means the soil – and the toxins miners use to extract minerals – runs directly into the river when it rains.

“What happens is that you remove this protection,” Rêgo da Silva said. “And we have a big problem with the use of mercury in mining. That soil that is entering the water is rich in mercury and other minerals too.”

While Rêgo da Silva says it’s  difficult to establish a direct link, many environmentalists in the area believe  the mercury is likely a key contributor to the dwindling number of fish in Rio Fresco – a sentiment that some global studies echo. Across Brazil, as much as 221 metric tons of mercury are released into the environment each year due to illegal mining, preliminary studies showed in 2018.

Scientific studies have also found mercury to be detrimental to human health, linking exposure to the element to skin disease, infertility and birth defects. It can also impact river-dwelling communities far beyond the immediate area around a mining site, as contamination travels downstream and the impact becomes amplified up the food chain.

In Pará, the contaminated water flows from one river into the next, eventually reaching São Félix do Xingu. In the open water where Rio Fresco meets Rio Xingu, the blue stream of one flows alongside the muddy currents of the other.

“How can you use the water?” de Assunção wondered. “For whoever lives here, it’s impossible.”

Decades of damage

The decline of Rio Fresco didn’t begin this year with the spike in mining activity in this part of the Brazilian Amazon. Instead, it goes back to the mining rush that gripped the broader Amazon region beginning in the 1970s.

As new roads were built across the Amazon, the path into the mineral-rich lands around Ourilândia do Norte and Tucumã was opened up by miners searching for gold, nickel and iron. In the decades that followed, more and more miners moved into the area, hoping to strike it rich in the illicit gold trade.

Today, there are more than 450 illegal mines in the Brazilian Amazon, according to the Rede Amazónica de Información Socioambiental Georreferenciada (RAISG), a consortium of civil society organizations. Brazilian authorities estimate that 30 metric tons of illegal gold – worth about 4.5 billion reais ($1.1 billion) – are traded each year just in the Tapajós Basin, much of which lies in Pará state.

While mining accounts for  a far smaller proportion of deforestation than cattle ranching or logging, its environmental impact has become clearer – and more worrying – in recent years. A 2017 study found that mining contributed to about 10 percent of deforestation in the Brazilian Amazon between 2005 and 2015. The vast majority of mining-related clearing – about 90 percent – occurred illegally outside mining leases granted by the Brazilian government.

Most often, miners come with heavy machinery, including excavators, that can raze large swaths of forest with ease. Often, they also carve out makeshift airstrips, allowing mining supplies and equipment to be flown into densely forested areas by plane. When the land begins to yield less, they move on to another patch of mineral-rich forest.

Some of the mining in the region is legal but even those operations have run into controversy. Earlier this year, prosecutors suspended a nickel mine owned by mining giant Vale following contamination of a nearby river in the Xikrin indigenous territory. Vale has denied that its mine, which straddles the municipalities of Tucumã and Ourilandia do Norte, is responsible for the contamination.

Meanwhile, the area where illegal miners have recently ramped up their activity overlaps with the Kayapó indigenous territory, a vast region spanning some 3.28 million hectares that is home to several indigenous groups, including some that live in voluntary isolation from the outside world.

In Brazil, it is illegal to mine on indigenous lands – but local sources claim this isn’t stopping illegal garimpeiros from encroaching on the Kayapó territory. Some indigenous people who live on this land have been battling to expel the invaders in recent years. Others have reluctantly tolerated the illegal mining in exchange for a cut of the profits, which they say brings badly-needed funds to their communities.

Deforestation has more than doubled in the Kayapó protected area since 2000, with nonprofit groups pointing to gold mining as the key driver. FUNAI, the government agency tasked with protecting the interests of indigenous people in Brazil, has identified almost 3,000 people contaminated by mining residue in the territory.

Along Rio Fresco, the long-term impacts of mining pollution have also started to become evident. A study done by researchers at Unifesspa, led by Rêgo da Silva, recently found only 21 invertebrate species still living in Rio Fresco. In contrast, there were roughly 45 species in Rio Xingu. Aquatic invertebrates – often the larvae of flying insects – are routinely used by researchers as indicators of waterbody health. 

“This isn’t just an environmental problem – it’s also a social problem,” said Cristian Bento da Silva, an anthropologist with the Instituto de Estudos do Xingu, who is studying the impact of water pollution on the São Félix do Xingu community. “In the early 2000s, it was still possible to fish in Rio Fresco. Now, this river is known as the ‘Dead River’ here.”

As Rio Fresco became more polluted and the number of fish dwindled over the last two decades, de Assunção says many fishermen who relied on its waters have moved further along Rio Xingu in search of more plentiful catch.

“The veterans, the majority have left. Because it became impossible to work as the mining picked up,” he said, noting that there’s also been instances of illness in the community, which he blames on the polluted water.