News Release

Artisanal gold mining and Amazon sediments

Peer-Reviewed Publication

Proceedings of the National Academy of Sciences

Satellite Images from the Dry Season in the Madre De Dios Region

image: Satellite images from the dry season in the Madre de Dios region show the increase in deforestation and suspended sediment concentration in rivers (orange) associated with artisanal scale gold mining activities from 1984 to 2019. view more 

Credit: Landsat imagery courtesy of NASA Goddard Space Flight Center and US Geological Survey

Researchers report environmental impacts of artisanal-scale gold mining (ASGM) in a tropical biodiversity hotspot. ASGM, which has been expanding worldwide, often facilitates deforestation and can lead to increased sediment transport into nearby rivers. The subsequent impacts of ASGM on river hydrological properties in tropical systems, such as the Peruvian Amazon, are not well understood. Evan Dethier and colleagues examined 34 years of satellite images to determine the effects of ASGM on suspended sediment concentrations (SSC) in 32 river reaches in the Madre de Dios River (MDDR) watershed in the Peruvian Amazon, a global biodiversity hotspot. Eighteen of the sites were classified as affected by ASGM, with a significant amount of upstream deforestation associated with ASGM activity. The authors observed significant increases in SSC in 16 out of 18 affected sites. By contrast, only 5 out of 14 unaffected sites exhibited significant SSC increases. Increases tended to be large during the dry season, when SSC at unaffected sites is low, leading to inversion of natural seasonal SSC cycles. Such increases in SSC and the resulting elevated turbidity are likely to affect fish community structure. Additionally, ASGM-associated sediments tend to be associated with mercury and their increase may facilitate mercury transport to nearby communities. The results suggest that ASGM has contributed to deteriorating water quality in the MDDR region, and provide a framework for further evaluating environmental impacts of ASGM worldwide, according to the authors.

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Article #19-07842: "Heightened levels and seasonal inversion of riverine suspended sediment in a tropical biodiversity hot spot due to artisanal gold mining," by Evan N. Dethier, Shannon L. Sartain, and David A. Lutz.

MEDIA CONTACT: Evan N. Dethier, Dartmouth College, Hanover, NH; tel: 413-441-7476; e-mail: evan.n.dethier.gr@dartmouth.edu


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