This event is part of our ongoing Thursday Seminar Series.

Preview: One of the most immediate threats to the Peruvian Amazon–a global biodiversity hotspot–is illegal artisanal and small-scale gold mining (ASGM), which results in widespread land cover change. In ASGM, forests are cleared, rivers are dredged, and mining ponds are created. Gold is isolated using mercury, a potent neurotoxin, which then enters the aquatic and terrestrial ecosystem via atmospheric deposition or from contaminated tailings. Consequently, ASGM activity represents the largest global source of anthropogenic mercury emissions. While previous studies have shown widespread deforestation and mercury contamination from ASGM, little is known about how ASGM changes the hydrologic landscape and how mercury loading and transformation processes differ across these environments. Little is also known about the fate and impact of these atmospheric mercury emissions within forests located near ASGM. We analyzed remote sensing imagery of the Peruvian Amazon over the past 35 years and collected water samples from a 200-km reach of the Madre de Dios River, its tributaries, and surrounding oxbow lakes and mining ponds in areas both upstream and downstream of ASGM activity. We used these data to examine how the creation of ASGM-associated ponds impacts mercury transformations into the more bioavailable form of methylmercury within aquatic ecosystems. We then collected bulk precipitation, throughfall, litterfall, soil, and songbird feathers from locations near and far from ASGM activity in the Madre de Dios region of Peru. We used these data to determine whether atmospherically transported mercury derived from ASGM activity is entering local forest soils and food webs. These results raise important questions about the impact of mercury pollution on both aquatic and terrestrial ecosystems as well as for indigenous communities and wildlife that depend on them.

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