Study warns mining boom choking hundreds of rivers worldwide

By Stephen Beech via SWNS

Hundreds of rivers are being choked with sediment due to a mining boom, warns a new study.

Gold and mineral mining is degrading waterways in 49 countries across the tropics, according to the findings.

The new wave of excavation is having negative impacts on the environment in the form of deforestation, erosion, and the transmission of sediment downstream, say scientists.

They said their findings, published in the journal Nature, represent the first physical footprint of river mining and its hydrological impacts on a global scale.

Study first author Dr. Evan Dethier said: "For hundreds, if not perhaps, thousands of years, mining has been taking place in the tropics but never on the scale like we've seen over the past two decades.

"The degradation of rivers from gold and river mining throughout the tropics is a global crisis."

For the first part of the study, Dr. Dethier and his colleagues analyzed river mining across the tropics from 1984 to 2021.

They looked at the media and literature, mining company reports, social media, and satellite imagery.

The team recorded more than 7.5 million measurements of rivers around the world to map mining areas, and deforestation and sediment impacts. They also identified target minerals at the mining sites.

The results show that there are around 400 individual mining districts in 49 countries across the tropics.

More than 80 percent of the mining sites are located within 20 degrees of the equator in South America, Africa, Asia, and Oceania.

The team found a major uptick in mining in the 21st Century, with the emergence of mining at 60 percent of the sites after 2000, and 46 percent after 2006, coinciding with the global financial crisis.

For the second part of the study, the research team assessed the magnitude that mining operations have had on the amount of suspended sediment in 173 affected tropical rivers.

The data showed that more than 35,000 kilometers of tropical rivers are affected by gold and mineral mining around the world.

Of the 500,000 kilometers of tropical rivers worldwide, about six percent of that length is affected by such mining.

Mining has also caused suspended sediment concentrations to double at 80 percent of the 173 rivers represented in the study, relative to pre-mining levels.

Dr. Dethier, who worked on the study while he was a postdoctoral researcher at Dartmouth College in the U.S., said: "These tropical rivers go from running clear either throughout the year or at least through part of it, to either being choked with sediment or muddy year-round.

"We found that almost every single one of these mining areas had suspended sediment transmitted downstream, on average, at least 150 to 200 kilometers (93 to 124 miles) from the mining site itself but as much as 1,200 kilometers (746 miles) downstream."

He said there are 30 countries that have both active river mining operations and large tropical rivers that are more than 50 meters wide.

In those countries, on average, 23 percent of the length of their large rivers is affected by mining.

In some countries, more than 40 percent of the total length of those large rivers is altered by mining, including in French Guiana (57 percent), Guyana (48 percent), plus Cote d'Ivoire and Senegal (40 percent).

The study also included rivers such as the Congo in Africa, the Irrawaddy in Asia, the Kapuas in Oceania, and the Amazon and Magdalena in South America.

Study senior author Dr. David Lutz, a research Assistant Professor of environmental studies at Dartmouth, said: "Many of these tropical rivers systems are very biodiverse places, if not some of the most biodiverse places on Earth and are still currently understudied.

"The challenge here is that there are many species that could potentially become extinguished before we even knew that they existed."

To evaluate the ecological impact of river mining in the tropics, the researchers examined environmental management guidelines used in the United States and elsewhere and applied the standards to their data.

Since mining began, they found that two-thirds of the rivers represented in the study exceeded the turbidity guidelines for protecting fish on 90 percent of the days or more, meaning the cloudiness of the rivers was higher than recommended.

Dr. Lutz said: "When rivers and streams experience high levels of suspended sediment, fish are unable to see their prey or predators and their gills may become choked with sediment and damaged, which can lead to disease or even mortality."

Co-author Professor Miles Silman said: "Our team's prior work has reported on how gold mining is a problem in the Madre de Dios region of the Peruvian Amazon, by poisoning wildlife and people.

"While gold mining has a lot of potential to lift people out of poverty, particularly on remote tropical frontiers, the way it is done now comes at a tremendous societal cost from environmental degradation, mercury pollution, and corruption and criminal networks.”

While gold is the principal target for miners and accounts for nearly 80 percent or more of the mining sites, mining along rivers in central and west-central Africa, particularly, in Angola, the Democratic Republic of the Congo, and Cameroon, makes diamonds the second most mined mineral in the tropics.

Many minerals used in mobile phones and electric-car batteries and are used in electronics- such as cobalt, coltan, tungsten, and tantalite - are mined in the Democratic Republic of the Congo.

Dr. Dethier added: "These minerals are becoming increasingly necessary as we transition away from fossil fuels to clean energy, so this is an important area to keep track of."