The South Pacific region, covering a quarter of the Earth’s high seas, is a treasure trove of biodiversity and a nexus of cultural heritage. The region is host to hundreds of seamounts, including one of the longest seamount chains on Earth – the Louisville Ridge – which stretches 4,300 km from the Pacific-Antarctic Ridge northwest to the Tonga-Kermadec Trench.
Seamounts—underwater mountains—are hotspots for biodiversity, supporting diverse and complex webs of life in our ocean. Habitat-forming, long-lived coral and sponge species, and the seamounts themselves, provide shelter and hunting grounds to species including sharks, whales and fish. The vast walls of seamounts interrupt ocean currents, pushing nutrients from deep in the sea to the ocean’s surface, fueling food webs and playing a key role in ocean mixing and carbon cycling.
Hydrothermal vents at Tomga: Despite the crushing pressure, extreme variations in temperature and complete lack of sunlight, live still thrives at hydrothermal vents in the deep sea. This is a diffuse flow site dominated by snails and sea anemones. (CC) Schmidt Ocean Institute.Seamount chains have also been found to match the migratory pathways of whales and seabirds, providing rutes in the open ocean. Seamount chains are important habitats and ‘ecological stepping stones’ for a variety of species including whales, sea turtles, corals, and a multitude of other species.
The Louisville Seamount Chain, comprising more than 80 seamounts, hosts a wide array of species including sponges, anemones, and numerous corals including long-lived black corals, all of which are indicator taxa to identify an area as a vulnerable marine ecosystem (VME). Despite this, as a habitat for the survival, functioning, spawning, and recovery of orange roughy populations, the Louisville Seamount Chain is highly susceptible to degradation caused by bottom trawling.
Salas y Gòmez and Nazca Ridge, with over 110 seamounts collectively stretching across 2,900km, are believed to host 82 species considered threatened or endangered, such as sharks and rays, birds, and marine mammals. Each seamount in the Salas y Gómez and Nazca Ridges has been found to have unique community compositions, with very few species shared from seamounts at opposite ends of the ridges.
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The South Pacific ocean has been a cradle of life and culture for Indigenous Peoples and coastal communities for centuries. According to Kanak belief, seamounts must remain undisturbed as the resting place of the spirits of elders, while many Pacific peoples see islands and seamounts as beacons to guide departing spirits. Indigenous knowledge of marine environments, passed down through generations, forms an invaluable ocean wisdom that should guide our approach to marine conservation and sustainable fisheries.
Why Protection is Crucial
The preservation of seamounts and other vulnerable marine ecosystems (VMEs), including hydrothermal vents and cold-water corals, supports global ocean health and the protection of vast biodiversity. However, these ecosystems are incredibly vulnerable to human impacts and continue to face significant threats including industrial bottom trawling and climate change.
Bottom trawling has devastating impacts on seamount ecosystems. The heavy trawl gear physically scrapes and destroys habitats that can be thousands of years old and can take centuries to recover, if at all. This disruption affects not only the structural integrity of the ecosystem but also the species that depend on these habitats for food and shelter. Bottom trawling also stirs up sediment, which can smother nearby organisms and alter nutrient cycles.
Rising temperatures stress cold-water species, while acidification weakens coral and shell-forming organisms crucial to these habitats. Decreasing oxygen levels create oxygen-starved hypoxic zones, and altered nutrient circulation disrupts food chains, endangering the many unique and endemic species that seamounts support. These changes risk biodiversity loss and undermine seamounts’ role in global carbon cycling.
Protecting seamounts and other vulnerable marine ecosystems of the deep sea would realize UN General Assembly resolutions committing States to the protection of these ecosystems from destructive fishing practices and global frameworks, such as the Convention on Biological Diversity’s Global Biodiversity Framework and the High Seas Treaty.
Given the transboundary nature of these ecosystems, international cooperation is vital for protecting the numerous vulnerable and fragile ecosystems in the region. Collaborative efforts between governments, scientists, Indigenous communities, and conservation organizations can ensure that the region’s resources are utilized sustainably while preserving its biodiversity and cultural heritage.
The thirteenth meeting of the Commission to the South Pacific Regional Fisheries Management Organisation (SPRFMO) meets in Santiago, Chile, from 17-21 February, 2025. SPRFMO is responsible for the conservation and management of high seas fisheries in the South Pacific Ocean, and for safeguarding the marine ecosystems of this area.