Co-production of contaminated landscapes: anthropogenic loading and food web structure drive mercury bioaccumulation in abandoned gold mines

Artisanal and small-scale mining is a significant and growing livelihood across the global South, which all too often leaves a legacy of contaminated landscapes. Given the increasing reliance of economies on metals and minerals, it is critical to understand what controls contamination outcomes in this rapidly developing extractive practice. Here, we demonstrate that the emerging concept of co-production offers a novel way to elucidate the joint contributions of natural and societal factors in shaping contaminant exposure from artisanal and small-scale mining. Specifically, understanding the co-production of contaminated landscapes requires attention to both the political economy of mining, including how labor and extraction methods differ across mines, as well as the sources and pathways of mercury exposure. In Madre de Dios, Peru, we measured mercury levels in wildlife inhabiting abandoned gold mining sites worked with different extraction technologies. We found that the type of technology used, whether heavy machinery or suction-pump based, influenced mercury loading into mines, and together with differences in food-web structure, mediated mercury biomagnification rates. Mercury concentration increased 2.1 to 3.7-fold per trophic level, and bioaccumulation levels were high in both mined and unmined sites—indicating elevated background levels in the region. We also found evidence of lateral transfer of mercury from abandoned mining pits to terrestrial food webs. This observation indicates that the footprint of mercury contamination extends well beyond individual mines, affecting the larger landscape. Our findings underscore the necessity of understanding the entangled ways in which social and ecological factors contribute to the production of toxic landscapes.