Gold and mineral mining in and near rivers across the tropics is degrading waterways in 49 countries, according to a Dartmouth-led study. Published in Nature, the findings represent the first physical footprint of river mining and its hydrological impacts on a global scale.
Shallow mining ponds overwhelm a former river system in the La Pampa region of Madre de Dios, Peru. The colors of the ponds reflect suspended sediment and algae growth following the cessation of gold mining. Credit: Jason Houston
"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," says first author Evan Dethier, an Occidental College assistant professor, who worked on the study while he was a postdoctoral researcher at Dartmouth. Dethier has a Ph.D. and MS in earth sciences from Dartmouth's Guarini School of Graduate and Advanced Studies.
For the second part of the study, the researchers assessed the magnitude that mining operations have had on the amount of suspended sediment in 173 affected tropical rivers. To detect the transport of suspended sediment using Landsat data, the team appliedThe data shows 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 6% of that length is affected by such mining.
"To give you an idea of how far the sediment can travel downstream, this is nearly comparable to the distance from Bangor, Maine, to Richmond, Virginia," says Dethier. To evaluate the ecological impact of river mining in the tropics, the team examined environmental management guidelines used in the U.S. and elsewhere and applied the standards to their data.
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