THE Lost CITY

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 is 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.

In the year 2000, oceanographers exploring the mid-Atlantic ridge stumbled across something amazing: a field of massive hydrothermal vent chimneys. Located high on the upper slopes of the Atlantis seamount massif, the complex of white mineral chimneys rises 4,300 metres from the bottom but still 750 metres below the surface.

The 30 chimneys, collectively known as the Lost City, extend across an area of 500 m2 and come in many shapes and sizes. The largest, christened ‘Poseidon’, measures 60 by 100 metres, while another, named ‘Beehive’ for its shape, is just one metre tall. The ‘IMAX’ chimney, by contrast, is around 8 metres tall but supports mineral pillars stretching as high as 30 metres.

Some of the chimneys vent hot fluids from holes in their sides, but these are not the underwater volcanoes you might have been expecting. In fact, they are the result of a much rarer phenomenon – and could hold vital clues to the origin of life itself.

To describe what is occurring in simple terms, water far below the seafloor is reacting with rock in the Earth’s mantle, and changing its molecular structure to turn it into a new form of ‘serpintinite’ rock. The chemical process involved generates hydrogen and methane and a lot of heat, all of which are discharged in highly alkaline water escaping through vents in the seafloor. The mineral deposits in this geothermally-heated water then gradually begin to form into chimneys above the vents. It is thought that the chimneys of the Lost City are more than 120,000 years old – relatively young compared to the two-million-year-old Atlantis massif they sit on. 

Geologists, chemists and biologists are all very interested in what is going on down in the Lost City, speculating that places like this could be where life on Earth began.  The chemical reactions which take place during serpentinization are capable of supporting an entire ecosystem teeming with life – all without depending on energy from the Sun. Moreover, the same process is thought to occur on other planets, including Mars – so research in the Lost City could even help us search for clues to finding life in outer space.

Researchers are also interested in learning more about so-called ‘extremophiles’ – organisms which thrive in extreme conditions. In the Lost City, the heat, alkaline water, lack of light and high pressure combine to create an environment that is extreme by any definition – and yet in terms of biodiversity it is thriving: There is a lot more than just rock down there. The unique chemistry and geology at the site create a one-of-a-kind ecosystem which in turn supports rich biodiversity, with bacteria living inside and outside the vents and trillions of microorganisms subsisting on the hydrogen and methane they emit. Despite the harsh environment corals, snails, bivalves, crabs, shrimp and jellyfish can be found there, while neighbouring habitats play host to larger fauna including visiting wreckfish, grenadiers, sharks and arrowtooth eels. Many of the species are only found in this location, with rates of endemism approaching 60 percent.

Threats and the future

There are no other known sites in the world quite like the Lost City, and several different international bodies are united in their determination to protect it. In 2014, it was recognized as an Ecologically or Biologically Significant Marine Area under the Convention on Biological Diversity, scoring on five of the seven criteria. Two years later, UNESCO proposed it as a possible World Heritage site of ‘outstanding universal value’, calling for a 20 km buffer around the area and citing its aesthetic importance, its place in Earth’s history, its significant ecological and biological processes, and its biological diversity and threatened species. It has also been named both a Mission Blue Hope Spot, and a High Seas Gem by the Marine Conservation Institute; Greenpeace and the IUCN have also called for it to receive special protection. 

The complex topography of the Lost City has prevented commercial fishing in the area, making the deep-sea mining industry the dominant threat to this fragile site. In 2018, the International Seabed Authority (ISA) approved a licence for Poland to explore 10,000 km2 of vents along the mid-Atlantic ridge in search of cobalt, manganese, gold and other heavy metals. While the Lost City itself is not currently part of the Polish plans, far-reaching sediment plumes and discharges from mining activity could still cause massive damage to this unique habitat – or to similar sites that have yet to be discovered.

The ISA is theoretically required to take measures to protect the marine environment against the harmful effects of mining, and by the terms of its licence, Poland is obliged to undertake environmental baseline and monitoring studies.  Still, many are questioning the efficacy of the supposed safeguards in place. 

Encouragingly though, exploration is only in its early stages and there is still time to ensure this remarkable place receives the strict protection it needs. Because the Lost City is a shared global treasure, we can only effectively protect it for ourselves and future generations through an international treaty, with its eventual designation as a high seas MPA as an urgently needed next step.