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.
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 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.”
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