Indonesia’s illegal gold boom leaves a toxic legacy of mercury pollution

MERANGIN, Indonesia — There wasn’t much Aris Adrianto felt he could do when the gold miners’ heavy vehicles broke into Bukit Gajah Berani, here in this remote pocket of Sumatra’s Merangin district.

“They just kept going, like they were afraid of nothing,” said Aris, who is the head of the forestry office in Birun village in the Sumatran province of Jambi.

Aris reported the deforestation of Bukit Gajah Berani, a forest whose name means “the hill of the brave elephant,” but nothing changed, he told Mongabay Indonesia.

Heightened political risks and giddy company valuations propelled the international price of gold, traditionally viewed as a safe haven asset during nervy economic times, up by almost 70% last year to more than $4,500 per ounce.

Around the world, that shine has likely induced a dangerous response as people on the ground, like Aris, report an expansion of illegal gold mining, undermining international commitments to curb deforestation and improve public health.

In Bukit Gajah Berani, Aris watched on as the miners turned the forest upside down, altering the landscape from a deep green to a sallow muddy brown.

The Bukit Gajah Berani forest is a buffer contiguous to Kerinci Seblat National Park, the largest old-growth rainforest in Sumatra — a high-conservation-value protected area and the largest intact habitat of the critically endangered Sumatran tiger (Panthera tigris sumatrae).

The forest here is a small part of a vast total area of landscape that fell victim to mining this century.

Analysis by Nusantara Atlas, a nonprofit remote-sensing platform, estimated that 721,000 hectares (1.78 million acres), including 150,000 hectares (371,000 acres) of old-growth forest, were cleared by miners across Indonesia between 2000 and end-2023. Surface and underground coal mines accounted for almost half of that total, but digging for gold accounted for around one-fifth.

Recent Mongabay reporting has documented rising disease burdens in illegal mining sites, community breakdown and violence, and expansion into old-growth forest by major gold-mining companies.

The public health impacts can be diverse and unexpected. Last year, Mongabay Indonesia reported malaria diagnoses surged from 32 cases in 2022 to 815 in 2023 at one gold-mining area in the province of Gorontalo, on the island of Sulawesi.

However, a large share of the public health burden borne by miners and local populations remains down to mercury, a heavy metal used to bind and extract gold particles from ore. The devastating consequences of that chemistry have been known for decades.

Death metal

In 1956, health workers in the Japanese port town of Minamata discovered a horrific new disease of the central nervous system.

It took the government of Japan more than a decade to acknowledge that the grim combination of symptoms resulted from people eating shellfish contaminated by the Chisso Corporation’s acetaldehyde chemical factory.

Acetaldehyde is a ubiquitous all-round precursor used as a building block in the manufacture of myriad consumer and industrial chemicals. It is used in the manufacture of plastics, insecticides, dyes and drugs. Acetaldehyde also flavors and preserves processed foods.

In the 1950s, the Chisso Corporation used mercury sulfate in its manufacture of acetaldehyde, a reaction that also yielded the byproduct compound methylmercury. Chisso simply dumped its wastewater into Minamata Bay, allowing methylmercury to accumulate in the food chain unnoticed until the people of Minamata began to suffer.

Doctors recorded the symptoms of Minamata disease as distal and diffuse: impaired vision, hearing and speech, and wasted muscles. Birth anomalies were common.

More than half a century later, in 2017, the Minamata Convention entered into force as a global framework to protect people by controlling the production, trade and use of mercury.

And in early November last year, countries gathered for five-day talks in Geneva, Switzerland, for the Conference of the Parties to the Minamata Convention on Mercury (COP-6).

COP-6 led to an international agreement to strengthen national action plans to contain mercury use and to phase out mercury in dentistry by 2034, which, if successful could cut up to 10% of current global demand for mercury (a 2017 report by the United Nations Environment Programme estimated global demand for mercury in dentistry at up to 322 metric tons per year).

Countries also committed to strengthen data collection and introduce new mercury-free technologies to the gold-mining sector.

Krishna Zaki of the Nexus3 Foundation, a nonprofit that works extensively to limit mercury in Indonesia, said most of the mercury in circulation in the country comes from cinnabar mining on western Seram Island, with some extraction to a lesser extent in parts of West Kalimantan and Southeast Sulawesi provinces.

Vermillion-colored cinnabar deposits in these areas of Indonesian can contain 70% mercury, among the highest concentrations in the world.

“Most of it is used for small-scale gold mining, which generally operates without any permits,” Krishna said.

At a public discussion in October 2025 on implementing the Minamata Convention, government and law enforcement officials acknowledged the need for stronger enforcement and institutional shifts to make Indonesia’s existing mercury measures effective.

Yunik Kuncaraning Purwandari, who leads the environment ministry’s working group on toxic substances, said the government has introduced alternatives to processing gold in several regions, using technologies from gravity concentration to cyanidation.

“On paper, our regulations are comprehensive, but on the ground, implementation is fragmented,” said Ratih Andrawina Suminar from the Attorney General’s Office in Banten, a province bordering Jakarta with numerous illegal mines. “Each agency operates on its own timeline, but this issue involves multiple sectors.”

The Nexus3 Foundations counts around 1,200 illegal mining locations in 190 districts, with mining taking place in 15 protected forests.

“Many officials and the public don’t yet view mercury as a dangerous substance on a par with narcotics,” Ratih said.

Krishna called on government agencies to shut down illegal cinnabar mines, restore contaminated land, establish secure mercury waste storage, and expand environmental and public health monitoring while cracking down on illegal actors.

Last year the environment ministry set up a new enforcement desk to counter illegal mining. Tens of thousands of medical devices containing mercury have been replaced in hospitals, officials say. However, criminal actors are adapting to law enforcement efforts on the ground.

“Sellers are now increasingly sophisticated, using new keywords to evade detection systems,” Yunik said.

In addition, several forecasters expect growth in the wider mercury market to persist, with some market research firms putting the annual increase in market size at more than 2% through this decade.

Peer-reviewed research published in the Journal of Material Cycles and Waste Management in 2023 noted a decline in both the supply and demand of mercury, but added that “the supply of mercury from primary mining has not decreased as much as initially expected.”

Under the Minamata framework, countries have submitted action plans to significantly reduce human mercury uses, but the sustained high price of gold is prompting more deforestation of areas like Jambi’s Bukit Gajah Berani.

In retrograde

Indonesia published its national action plan on reducing mercury under the government of then-president Joko Widodo in 2019. That document included an ambitious target to eliminate mercury from the illegal gold mining sector by 2025.

However, Indonesia remains one of the world’s largest producers and consumers of mercury — and the archipelago’s illegal mining sector is a globally significant source of mercury pollution.

Inventories of mercury emissions conducted in 2012 estimated the illegal mining sector then was responsible for 57.5% of the mercury emissions caused by humans in Indonesia (some mercury is released by processes such as volcanic eruptions and emissions from ocean vents).

More recent estimates indicate mining is to blame for the vast majority: 69.7% of Indonesia’s combined mercury emissions, an estimated release of 338.5 metric tons per year.

Studies in regions beset by illegal mining have found mercury concentrations in multiple fish species far above the World Health Organization’s safety limit of 0.5 milligrams per kilogram.

A peer-reviewed study published this year from Sukabumi district, just south of Jakarta, found mercury contamination in cassava, soil and water samples at levels several times above accepted safety limits. The district is home to numerous illegal gold mines.

In semiautonomous Aceh province, at the northern tip of Sumatra, the area quarried by illegal miners increased from 6,805 hectares to more than 8,000 hectares (16,816 to 19,800 acres) last year, said Ahmad Shalihin, who runs the provincial chapter of civil society group the Indonesian Forum for the Environment (Walhi).

That includes 1,882 hectares (4,651 acres) of illegal mining in the critical Leuser Ecosystem, a habitat for elephants, orangutans, rhinos, sun bears and tigers.

“The community doesn’t dare go against it because these activities involve many powerful actors,” said Ramadhan, a resident who lives near an illegal gold mine in Aceh’s southern Nagan Raya district.

In Bukit Gajah Berani, a fundamental change brought on by market forces appears to have altered the relationship sustained between people here and the landscape.

“People here used to just live off nontimber forest products,” said Deri Sopian, who also works at the village government’s forestry office in Bukit Gajah Berani.

“Now, around 30 hectares [74 acres] of the forest have been wrecked by illegal gold mining,” Deri said, an area the size of around 100 football fields.

Several politicians and civil society groups said land-use change, including illegal gold mining, has reduced the drainage capacity of northern Sumatra’s mineral soils, worsening floods from Cyclone Senyar, which killed at least 1,154 people in late November.

“The impacts affect the future of humanity and the planet we inhabit,” said Krishna from the Nexus3 Foundation.

Nuggets of information

Governments and environmentalists say this new rush for gold may be worsening an existing crisis, which is mostly hidden from view in the forests of Indonesia and the Amazon.

Early on Sept. 19, 2025, police pulled over a minivan on the Bangko–Kerinci Highway here near Bukit Gajah Berani and Birun village, where Aris Adrianto runs the local forestry office.

Officers seized 16 chunks of gold weighing a combined 1.7 kilograms (3.7 pounds), a consignment worth almost $200,000.

Taufik Nurmandia, a senior police officer at Jambi’s provincial police headquarters, said the three suspects in the vehicle had acquired the gold from someone in Perentak village and another person of interest in Merangin district, a fugitive at the time of writing.

Taufik said the network’s courier had made at least 10 gold runs up over the Barisan Mountains and down into the city of Padang, the capital of West Sumatra province, to meet with traders. The suspects would be charged under a mining law, and faced prison sentences up to five years, Taufik added.

Less than a fortnight later, on Sept. 30, a district court in neighboring Bangko sentenced trader Syamsir and courier Ahmadin Nuri to 11 months in prison and a 200 million rupiah ($12,000) fine after police thwarted a 1.2-kg (2.6-lb) illegal gold run to Padang in late May.

“As long as there are buyers, illegal mining will continue,” Taufik said. “That’s why we are not just taking action against the perpetrators in the field, but also against those who trade and store the results of illegal mining.”

Illegal mining also appears to be eating into local food production. The regional government statistics agency has recorded a sharp fall in rice production in recent years, with a harvest of 386,413 metric tons recorded in 2020 but only 275,950 metric tons in 2023. That production decline by weight has taken place alongside a reduction in the harvested area from 84,773 to 61,240 hectares (209,479 to 151,327 acres).

In 2022, the Merangin district government recorded 3,920 hectares (9,687 acres) of rice fields were damaged as a result of gold mining.

A Nexus3 Foundation report published in 2018 found mercury levels in rivers in four areas of Merangin district reached 0.01-0.02 milligrams per liter, significantly exceeding accepted health guidelines. Today, the nonprofit says more than 50,000 hectares (123,600 acres) in Jambi province have been destroyed by illegal mining.

“River water that used to sustain life for the community is now heavily polluted, the fish numbers have decreased,” said Sukmareni, a spokesperson with KKI Warsi, a civil society organization based in Jambi and West Sumatra province.

A decade ago, local authorities estimated 12,000 hectares (nearly 30,000 acres) of community land was damaged every year by illegal mining here in Merangin, one of 11 devolved district and city governments in Jambi province. That’s equivalent to the land area of the U.S. city of San Francisco.

In 2022, the government sought to arrest the crisis in Jambi’s forests by providing a pathway for the illegal community mines to achieve formal status. By 2022, more than 7,000 hectares (17,300 acres) were zoned as areas where “community mining” could take place.

However, at the time of writing, not even one community in Jambi had received a community mining permit, said Feri Irawan, director of nonprofit Assosiasi Hijau.

“The facts on the ground now are that the area is being worked by illegal miners,” Feri said, adding that community mining concept “exists only on paper.” He called on Jambi Governor Al Haris to initiate a crackdown to remove heavy machinery from Jambi’s forests.

Many here in Merangin district say they worry that allowing illegal gold mining to expand in order to generate one-off, untaxed revenues by criminality eats away at the food production base and pollutes waterways for a generation.

“Forest-grown coffee, forest honey and rattan are proven providers of income without destroying nature,” Sukmareni said.

“Children are losing the resource to learn from nature, they are losing the land they will inherit,” she added. “And they are inheriting a heavy ecological burden.”

Banner image: Rescuers search for victims at the site of a landslide in Suwawa on Sulawesi Island in July 2024. Image by AP Photo/Basarnas.

This story was first published here, here and here in Indonesian on Oct 7, 18 and 20, 2025.

25-fold surge in malaria at Indonesia gold frontier raises deforestation questions

Indonesian gold mine expanding in ‘wrong direction’ into orangutan habitat

Citations:

Sodeno, R. (2023). Projected global mercury supply, demand, and excess to 2050 based on impacts of the Minamata Convention. Journal of Material Cycles and Waste Management, 25, 3608-3624. doi:10.1007/s10163-023-01780-y

Agustiani, T., Sulistia, S., Suciati, F., Sudaryanto, A., Amandita, F. Y., Efadeswarni, … Agusa, T. (2025). Comprehensive assessment of mercury contamination and health risks from artisanal and small-scale gold mining (ASGM) in Sukabumi, Indonesia. Earth, 6(3), 110. doi:10.3390/earth6030110

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