THE WEIGHT OF GOLD: PERUVIAN FORESTS PAY THE PRICE FOR ARTISANAL-SCALE MINING

The Amazon rainforest has suffered from decades of unsustainable land-use practices, combined with the growing effects of climate change. Artisanal scale gold mining (ASGM) is a major driver of deforestation across the Amazon, particularly in southeast Peru. Forest loss is not the only consequence; excavation, sluicing, and mercury usage to amalgamate gold have resulted in the expansion of fluvial systems and a decline in water quality. The chronology of ASGM throughout Peru has been well-studied, along with a range of environmental impacts including carbon loss, pollution, and downstream sedimentation. However, little is known about the latent hydrological legacy of ASGM, which may have enduring impacts on the health and resilience of the Amazon and its aquatic systems.

To address this, a combination of field and remote sensing techniques was employed in the southeast portion of the Madre de Dios (MDD), chosen due to its severe mining activity surrounding many important headwaters of the Amazon River. In-situ measurements over 54 selected sites found a significant increase in hydraulic conductivity in response to ASGM-induced deforestation. Paired electrical resistivity tomography measurements in these areas further indicate low subsurface water availability due to the highly permeable landscape, posing a challenge to natural regeneration and reforestation efforts. Outside of the directly impacted regions, Landsat imagery shows that in the periods following gold mining, there is a transition of surrounding primary forest into oversaturated channels and standing dead biomass. Thus, ASGM has deprived soils of vegetation-sustaining moisture, while lowering the productivity of other regions through inundation. By documenting these effects, this investigation will inform forest recovery strategies in areas impacted by and adjacent to mining activity, assisting in the development of restoration conditions concerning plant choice and soil and water management.