Integrated assessment identifies pathways for effects of deep-sea nodule mining across ocean and seafloor ecosystems

Seafloor mineral resources offer a potential novel source of critical metals ^1,2 . However, uncertainty about the potential impacts of deep-sea mining on marine ecosystems has led to increasing calls for a scientifically rigorous framework to assess environmental effects ^3–6 . Here, we provide a framework for the first integrated ecosystem assessment of the Clarion-Clipperton Zone (CCZ) — a region of the equatorial Pacific with 17 active exploration areas for potential mining of seafloor polymetallic nodules (totalling ~1.2 million km ² ). We present a comprehensive model of ecosystem structure in the CCZ, extending from the ocean surface down to the abyssal seafloor (~3,500–5,500 m depth), to identify the potential impacts of mining activities on ecosystem components, functions, and services. Our assessment shows that adverse effects could occur within and proximal to directly mined areas, including sustained changes in seafloor communities due to substrate removal and sediment redeposition. However, our analysis did not identify any functional pathways that could transmit effects from the abyssal seafloor to the upper ocean. We identify ecosystem indicators to assess the impacts of a prototype mining system, informing the development of environmental management and monitoring plans before the potential onset of industrial-scale mining in the deep sea.