The Salas y Gómez and Nazca ridges: A review of the importance, opportunities and challenges for protecting a global diversity hotspot on the high seas

The Salas y Gómez and Nazca ridges are two seamount chains of volcanic origin, which include over 110 seamounts that collectively stretch across over 2,900 km in the southeastern Pacific. Ecosystems in this region are isolated by the Atacama Trench, the Humboldt Current System, and an extreme oxygen minimum zone. This isolation has produced a unique biodiversity that is marked by one of the highest levels of marine endemism on Earth. These areas also provide important habitats and ecological stepping stones for whales, sea turtles, corals, and a multitude of other ecologically important species, including 82 species that are threatened or endangered. Recent explorations in this region have documented one of the deepest light-dependent marine ecosystems on Earth, as well as numerous species that are new to science. Waters surrounding the Salas y Gómez and Nazca ridges are mostly located in areas beyond national jurisdiction (ABNJ), with smaller portions located in the national waters of Chile and Peru. Within this region, Chile has already protected all the ridge features that fall within its jurisdiction, and Peru is evaluating a proposal that would protect the seafloor that falls within its national waters. However, all of the ABNJ in the region, which cover over 73% of the Salas y Gómez and Nazca ridges, are unprotected and under threat from a variety of stressors, including climate change, plastic pollution, overfishing, and potential deep-sea mining in the future. Importantly, fishing and other commercial activities are at low levels in international waters of this region, so there is a time-sensitive opportunity to protect its unique natural and cultural resources before they are degraded. This study provides a synthesis of the relevant science that has been conducted on the Salas y Gómez and Nazca ridges, and discusses the opportunities and challenges for protecting this unique region via existing sectoral organizations and through the emerging international agreement on biodiversity beyond national jurisdiction (BBNJ). Given its exceptional natural and cultural significance, the Salas y Gómez and Nazca ridges should be comprehensively protected from exploitation, pollution and other anthropogenic threats using the best available conservation measures