WALVIS
RIDGE

Salas y Gómez and Nazca ridges

Imagine a mountain range the length of the southern Andes –110 volcanic peaks, stretching nearly 3,000 km end to end. Imagine these mountains are filled with rare, spectacular wildlife, that nearly half the species they shelter live nowhere else on Earth, and that scientists are discovering new life forms with every expedition. 

Now stop imagining, because these mountains are real: they’re called the Salas y Gómez and Nazca ridges, and are deep in the waters of the South East Pacific.

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These two unique chains of submarine slopes and summits areseparated from South America by the rich, cold waters of the Humboldt Currentand the yawning abyss of the Atacama Trench. Numerous studies have concluded they’reamong the most ecologically significant areas in the high seas – those areas ofthe ocean that lie beyond the jurisdiction of any country. Far below the waves intricategardens of slow-growing corals and gorgonians adorn the rocky slopes in some ofthe clearest waters on the planet, and in the plankton-abundant upwellings overthe ridges sharks, turtles, whales and seabirds gather to forage. This uniqueregion is a vital habitat for commercial species too, from swordfish to jackmackerel, underpinning sustainable food security for millions – but only if welook after it.

Threats and the future

The Salas y Gómez and Nazca ridges are still largely ecologically intact, but biodiversity and ecosystem resilience are never the less under threat. Deep-water trawling has destroyed coral and seabed habitats down to depths of 2,000 m, and has taken a heavy toll in bycatch of animals and plant life alike. Floating plastic debris drives the risk of ingestion and entanglement for nearly 100 species. Meanwhile climate change is making the seas warmer, less oxygenated and more acidic, all of which pose an existential threat to marine biodiversity .

Ominously, there’s cobalt in the crusts of the Salas y Gómezand Nazca ridges, which the deep-sea mining lobby may one day step up effortsto exploit – but doing so would be an ecological disaster.  

We’ve got a time-sensitive window of opportunity. By permanently closing the area to fishing and mining and establishing a high seas MPA, we can save the Salas y Gómez and Nazca ridges for ourselves and for future generations. And with 80% of the mountains still unexplored, there’s surely so much more for them to discover…

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Back to the surface

Emperor Seamounts

No mechanism yet exists to establish marine protected areas (MPAs) in the high seas. It’s critical that the new United Nations High Seas Treaty sets up a global process for the establishment and effective management of a wide-ranging network of MPAs, including highly protected areas where no harmful industrial activities are allowed.

‘Walvis’ means ‘whale’ in Dutch and Afrikaans – the name an echo from the past reminding us how important this part of the Atlantic once was to the whaling industry. Today, with commercial fleets consigned to history, cetaceans are once more frequently encountered around the Walvis Ridge: southern right whales, fin whales and humpbacks are among its charismatic visitors.

The Walvis Ridge itself is a chain of seamounts running 3,000 km southwest from the coast of Namibia to the mid-Atlantic Ridge, which it meets around Tristan da Cunha and the Gough Islands. Plumbing depths down to 4,000 m, the Ridge comprises various seafloor types and includes many deep-sea features along with its abyssal plains, seamounts and guyots – steep canyons, embayments, a graben and fossilized cold-water coral reef mounds all contribute to its complex topography, creating a wide range of habitats for a wide variety of species. Biodiversity is particularly rich in the northeast section of the Walvis Ridge thanks to the Benguela Current, which transports nutrients and drives upwellings.

While the Ridge as a whole remains largely unexplored – a lot of what we know about its marine fauna in fact comes from commercial and exploratory fishing expeditions – it’s clearly a vital area for biodiversity. Bluefin and bigeye tunas along with orange roughy have been important species here for commercial fishers, who also operate fisheries for stocks including alfonsino, Patagonian toothfish, pelagic armourhead and deep-sea red crab. But this is only the beginning of the inventory. One research cruise identified a total of 175 fish species, 50 cephalopod species, and 192 benthic invertebrate species; while in the sky the productivity of the waters sustains globally threatened albatrosses as well as several species of seabirds endemic to the Tristan da Cunha islands.

Lophelia, goronian and bamboo corals are among those which have been discovered growing at various heights on the seamounts of the Walvis Ridge; the mounts acting as stepping stones which allow sedentary species like corals and sponges to gradually disperse over large distances.

Threats and the future

Despite the likely presence of vulnerable marine ecosystems (VMEs) on much of the Walvis Ridge, research on their extent has to date been very limited. The Scientific Committee of SEAFO, the regional fisheries management organization responsible for managing fisheries on the ridge, recommended the temporary closure of the area to all bottom trawling and gill netting, but SEAFO chose to go against the advice of its own scientists and has so far only closed a few nearby VME areas around the Wust Seamount. Sensitive habitats and the species which depend on them remain unprotected, and while the overall fishing footprint has so far been relatively small, there is heavy fishing in the northeast.

Fishing is not the only cause for concern. Drilling for offshore oil and gas has already taken place in Namibia’s EEZ, and this is likely to be extended in future. Next to the Ridge, deep on the Cape Abyssal Plain, ferromanganese nodules may one day attract the unwelcome attentions of the deep-sea mining industry. Sediment plumes and pollution from such activities could have a serious impact on the fragile ecosystems of this chain of mountains under the sea.

Nevertheless, there is cause for hope. The UK’s protection in 2020 of a vast area around Tristan da Cunha – which created the largest no-take zone in the Atlantic – should add momentum to regional marine conservation efforts. As an Ecologically or Biologically Significant Area (EBSA) which connects to this same island group, the Walvis Ridge is a natural priority for protection to further strengthen the resilience of the high seas. Because this unique and special place is a global common, we can only effectively protect this area for ourselves and future generations through an international treaty: designation as a high seas MPA is the obvious next step.