The global crisis of mining in tropical rivers

Abstract Rapidly increasing mining in rivers across the global tropics has major, interrelated consequences for ecosystems and human health. River mining involves intensive excavation and sediment processing in river corridors, altering river form and releasing excess sediment to river waters. Contaminants such as mercury and cyanide are used in some operations and are also released to the environment. Although river mining has been investigated at local and regional scales, no global synthesis of its physical footprint and impacts on hydrologic systems exists, so its full environmental consequences are not known. We assemble and analyze a 37 yr satellite database showing that river mining is pervasive globally. We identify 381 mining districts in 49 countries, concentrated in tropical waterways that are almost universally degraded. Of 173 mining-affected rivers, 80% have suspended sediment concentrations double pre-mining levels. In countries where mining affects large (>50 m wide) rivers, 23 ± 19% of large river length is altered by mining-derived sediment, a globe-spanning effect representing 5–7% of all large tropical river reaches. Mining intensity has rapidly increased during 21st-century global financial insecurity and rising demand for precious minerals. The ubiquity and intensity of mining degradation in tropical river systems is a global crisis.