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Research Highlights - Amazon Gold Mining

Scientists from Carnegie and the Peruvian Ministry of Environment have mapped the true extent of gold mining in the biologically diverse region of Madre de Dios in the Peruvian Amazon. The team combined field surveys with airborne mapping and high-resolution satellite monitoring to show that the geographic extent of mining has increased 400% from 1999 to 2012 and that the average annual rate of forest loss has tripled since the Great Recession of 2008. Until this study, thousands of small, clandestine mines that have boomed since the economic crisis have gone unmonitored. The research is published in the online early edition of the Proceedings of the National Academy of Sciences

The team, led by Carnegie’s Greg Asner in close collaboration with officials from the Peruvian Ministry of Environment, used the Carnegie Landsat Analysis System-lite (CLASlite) to detect and map both large and small mining operations. CLASlite differs from other satellite mapping methods. It uses algorithms to detect changes to the forest in areas as small as 10 square meters, about 100 square feet, allowing scientists to find small-scale disturbances that cannot be detected by traditional satellite methods.

The team corroborated the satellite results with on-ground field surveys and Carnegie Airborne Observatory (CAO) data. The CAO uses Light Detection and Ranging (LiDAR), a technology that sweeps laser light across the vegetation canopy to image it in 3-D. It can determine the location of single standing trees. This level of detail was used to assess how well CLASlite determined forest conditions in the mining areas. The CAO data were also used to evaluate the accuracy of the CLASlite maps along the edges of large mines, as well as the inaccessible small mines that are set back from roads and rivers to avoid detection. The field and CAO data confirmed up to 94% of the CLASlite mine detections.

The results reveal far more rainforest damage than previously reported by the government, NGOs, or other researchers. In addition to wreaking direct havoc on tropical forests, gold mining releases sediment into rivers, with severe effects on aquatic life. Gold mining has contributed to widespread mercury pollution affecting the entire food chain, including the food ingested by people throughout the region. Miners also hunt wild game, depleting the rainforest fauna around mining areas, and disrupting the ecological balance for centuries to come.

Zoom image of gold mining in 3D

A map of all gold mining in Madre de Dios from 1999-2012

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