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Peru’s crackdown on illegal gold mining a success, but only briefly, study shows

Gold mining in the Peruvian Amazon. Photo by Rhett A. Butler.

Gold mining in the Peruvian Amazon. Photo by Rhett A. Butler.

  • Peru’s state intervention against illegal gold mining in the Madre de Dios region succeeded in halting the activity for a couple of years, pushing miners into concessions allowing mining, according to recent research.
  • Operation Mercury, which ran between 2019-2020, led to the abandonment of almost all targeted illegal mining sites in La Pampa, an area found in the buffer zone of a major national park.
  • But while there’s been some forest regeneration in the affected areas since then, this has been undone by even higher rates of deforestation in the legal mining areas where the miners have moved into.
  • Experts also say the effort has been unsustainable, as law enforcement in the area has waned and miners have started to come back, with the COVID-19 pandemic playing a major role in cutting enforcement budgets.

Between 2019 and 2020, the Peruvian government cracked down on illegal gold mining in Madre de Dios, its southeastern Amazon region, through an unprecedented initiative dubbed “Operation Mercury.” But according to a recent study, miners have been returning to the areas that the operation had driven them from, as enforcement eased partly due to the COVID-19 pandemic.

The coordinated government effort resulted in a big win for the Peruvian state versus miners in La Pampa, a 100,000-hectare (250,000-acre) area located in the buffer zone of Tambopata National Reserve, an Amazonian park bursting with biodiversity. The zone sits on the southern side of the Interoceanic Highway, which connects Peru’s Pacific ports with Brazil’s Atlantic coast.

Artisanal gold mining, 90% of it illegal or informal, accounts for at least half of the economy in the sparsely populated region of Madre de Dios, and sustains around 50,000 miners, according to a 2022 study by USAID.

But the destructive activity has deforested at least 100,000 hectares of the Amazon Rainforest in Madre de Dios between 1990 and 2020, and it’s estimated that about 78% of adults in Puerto Maldonado, the state’s capital, have mercury levels above safe international standards, due to poor mining practices, according to the USAID study.

Deforestation in La Pampa caused by more than a decade of illegal mining. Image by Jason Houston for the International League of Conservation Photographers.

Since the start of Operation Mercury, which deployed 1,200 police officers, 300 soldiers and 70 prosecutors, deforestation caused by illegal mining dropped by 92% — from 173 to 14 hectares (427.5 to 35 acres) a month, according to satellite images from the Monitoring of the Andean Amazon Project (MAAP). Overall, following Operation Mercury, deforestation associated with gold mining decreased by 78% across six mining sites in Madre de Dios, including La Pampa, the same MAAP report found.

According to the recent study published in Conservation Letters, most miners operating in the raided areas crossed to the north side of the Interoceanic Highway, into an area where informal mining was permitted, known as the government-designated “mining corridor.”

The coordinated enforcement operation succeeded in its main goal of shutting down illegal mining operations and keeping out miners. Authorities set up three police bases in the zone and conducted regular antimining raids to destroy equipment and arrest miners, the report found.

“There was a very quick movement from La Pampa illegal zone across the road,” said study co-author Luis E. Fernández, executive director of Wake Forest University’s Center for Amazonian Scientific Innovation, based in Madre de Dios.

While the intervention was successful in stopping illegal gold mining activity in La Pampa, activity in legal areas spiked, triggering many of the same environmental concerns, particularly the use of mercury to extract the gold, the study said.

Limited success

“[Operation Mercury] was very effective in the area of operation,” said Fernández, who has been working on and off in Madre de Dios for more than two decades. “But there was no deterrent effect. It only controlled mining in one particular area: La Pampa. In the other areas, it was business as usual.”

“When you have a decision to govern mining then you can have people stop illegal activities and those activities can be moved to places where they are legal,” report co-author Miles Silman, a professor of conservation biology at Wake Forest, told Mongabay. “Which is exactly what Operation Mercury did, the miners that were in illegal areas went back to areas that were titled for mining. What happened is that the government didn’t follow through with the other stages.”

Illegal gold mining operations dominate the banks of - and fundamentally change the landscape and ecology of — the Madre de Dios River upstream of Puerto Maldonado, Peru. Photo courtesy Jason Houston/Upper Amazon Conservancy.
Illegal gold mining operations dominating the banks of  the Madre de Dios River upstream of Puerto Maldonado, Peru. Although the Peruvian government deployed Operation Mercury to tackle the phenomenon, its actions, though effective for a while, did not last long, due to a lack of continuous enforcement and the COVID-19 pandemic. Photo courtesy Jason Houston/Upper Amazon Conservancy.

Miners began to return to “areas controlled by the police, then into other areas,” Silman added, as enforcement dwindled during the pandemic because officers were deployed to enforce a strict lockdown.

“Conservationists sometimes focus too little on enforcement, but without enforcement, there’s no sustainability,” he said.

While Operation Mercury raids went on into late 2020, from the onset of the pandemic in March 2020 there was a reduction in military and police presence at the bases, and deep budgetary cuts.

“The pandemic started and that was the turning point,” said Martín Arana, a consultant for the Foundation for Conservation and Sustainable Development in Peru, who has researched illegal mining in the country. The pandemic was a “substantial setback” for financing Operation Mercury, as funds from all ministries were redirected to deal with the public health emergency.

The government of then interim president Francisco Sagasti tried to refloat the antimining initiative with “Plan Restoration.” But the multiple ministerial changes that came with the new government of Pedro Castillo, in office from July 2021 until he was impeached in December 2022, made maintaining a consistent policy near impossible. In 2019, funding for the “reduction of illegal mining” in Madre de Dios and other regions in the country amounted to 33 million soles ($9.9 million at the time); this year, it’s down to 8.4 million soles ($2.2 million), according to government figures.

“All the political instability which continues to this day means everything that had been achieved is lost,” Arana said.

A flooded gold mine in Madre de Dios, Peru. Photo by Claire Salisbury.

Following Operation Mercury, mining decreased by 70-90%, the study found, and for the next two years, the miners had virtually abandoned almost all the areas targeted. The number of excavated mining pits or ponds in illegal mining areas decreased by up to 5% per year, compared to increases of 33-90% per year before the intervention.

Deforested areas experienced revegetation at a rate of 100-300 hectares (250-740 acres) per year. Most of the revegetation occurred on the edges of deforested areas, with the highest revegetation in southern La Pampa. However, this progress was more than offset by increases in deforestation in legal mining areas north of the Interoceanic Highway. Here, forest was lost at rates of 300-500 hectares (740-1,240 acres) per year, and mining pond areas also increased by 42-83%.

Satellite monitoring

In order to assess Operation Mercury’s impact on mining activity, the research team drew on satellite data from 2016 to 2021.

Using radar and multispectral data, they were able to quantify changes in water, water quality, mining pond areas, and deforestation in La Pampa from before, during, and after the intervention.

Mining ponds typically show up as yellow to brown; this color is associated with high levels of suspended sediment in the water — a marker for gold mining activity, Fernández said.

“We use the color changes in the mining ponds as a proxy for [mining] activity,” he told Mongabay. As mining ceases and ponds are abandoned, the sediment settles, and the degree of yellowness diminishes — a pattern the researchers found in the raided areas following Operation Mercury.

“Conversely, when it turns back to a cappuccino color, we know it’s being mined again,” Fernández added.

Illegal and unregulated gold mining in the La Pampa area near Puerto Maldonado, Peru. Photo courtesy Jason Houston/Upper Amazon Conservancy.
Mining ponds in the La Pampa area near Puerto Maldonado, Peru. Image courtesy Jason Houston/Upper Amazon Conservancy.

Recent MAAP satellite images  show that mining infrastructure has returned, increasing by 400% in La Pampa compared to 2020. But unlike before, current mining takes place mostly in waste pits and lagoons because much of the forest cover has gone.

The return of illegal mining has brought with it the return of crime and violence, in many cases associated with transnational organized crime gangs. The vast majority of the mining activity is illegal or unauthorized, paying no tax and attracting crime groups involved in human trafficking, the sexual exploitation of underage girls, and modern-day slavery, Arana said.

“There are now bigger fish on the scene which are eating the previous ones,” he said, referring to the presence of new, more powerful organized crime groups.

Meanwhile, scientists continue to study the toxic impacts of residual mercury used in illegal gold mining. As wildlife returns to abandoned mining ponds, scientists are also studying the fallout, with results expected to be published soon.

“The worry is that you’re going to get the methylation of mercury as you start to build up organic matter, so you’re going to get a lot of mercury cycling,” Silman said.

As illegal gold mining continues to proliferate in the Amazon, Madre de Dios serves as an example that the state’s presence is key to controlling its spread, Silman said.


Dethier, E. N., Silman, M. R., Fernandez, L. E., Espejo, J. C., Alqahtani, S., Pauca, P., & Lutz, D. A. (2023). Operation Mercury: Impacts of national‐level armed forces intervention and anticorruption strategy on artisanal gold mining and water quality in the Peruvian Amazon. Conservation Letters16(5). doi:10.1111/conl.12978

Banner image: Gold mining in the Peruvian Amazon. Photo by Rhett A. Butler.

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Qualified success: What’s next for Peru’s Operation Mercury?

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