SAYA DE MALHA

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

The new High Seas Treaty sets up a global process for the establishment and effective management of networks of representative and well-connected marine protected areas in the High Seas, including highly and fully protected areas where no harmful industrial activities are allowed.

The Saya de Malha Bank is a shallow-water oasis in the heart of the Indian Ocean, midway between the Seychelles and Mauritius. Home to the world’s largest seagrass community, this unique seascape was named after the Portuguese for ‘mesh skirt’ 50 years ago by sailors who were amazed to find billowing meadows of seagrass teaming with life just a few meters below the surface in the middle of the vast deep ocean. And it is no wonder they were surprised; the Saya de Malha Bank is a rare example of seagrass meadows on the High Seas and the largest submerged ocean bank in the world, spanning more than 40,000 km2.

Centuries later, its remote location has allowed this spectacular ecosystem to remain relatively pristine, especially compared to coastal seagrass communities. Located on the Mascarene Plateau to the northeast of Madagascar, the bank is a biodiversity hotspot thanks to oceanic productivity, enhanced by the interaction of its topography and the South Equatorial Current. As well as seagrass covering 80-90% of its seafloor, the bank hosts extensive coral communities and encrusting red coralline algae, while more than 150 species of invertebrates and 100 species of gastropods
(a diverse class of molluscs) have been identified. Among the array of fauna are parrotfish, surgeonfish, rabbitfish, green sea turtles, wedge-tailed shearwaters, white-tailed tropicbirds, spotted dolphins, pygmy blue whales, and pilot whales. The coral reefs of Saya de Malha are a critical stepping stone for the migration of shallow-water species across the Indian Ocean, and sailors crossing the banks have reported that they are also a major breeding ground for sperm whales and blue whales.

There are undoubtedly many more species yet to be discovered, as the Saya de Malha Bank is one of the most isolated and least studied shallow marine ecosystems on Earth. Although the bank is about 35 million years old, according to volcanic dating, the first direct scientific study of the area was only made in 1997. Expeditions have since revealed that complex interplays between topography, tidal forces, and regional currents produce strong internal waves that deliver a rich supply of nutrients and plankton from adjacent deep waters. The area may also be a significant sink of atmospheric carbon dioxide due to its organic production being swept by currents into deeper waters, where much of it is buried in sediments. The Saya de Malha Bank could, therefore, become an important reference area for studying climate change and human impacts on the High Seas.

Threats and the future

The remoteness of the Saya de Malha Bank cannot protect it from broad-scale climate and oceanographic changes, which represent the biggest threat to this ecosystem. This was demonstrated in 1998, when the reefs were extensively damaged in a global mass coral bleaching event. Although they have recovered considerably since then, rising temperatures, increasing acidity, eutrophication, and changes in ocean currents all still pose a threat to the bank’s biodiversity. 

In 2018, the Joint Commission of the Mauritius-Seychelles Extended Continental Shelf opened the Mascarene Plateau region for oil and gas exploration. The Saya de Malha Bank likely contains reserves of oil and gas, prompting commercial interest in exploration and extraction, which could damage the ecosystem. Seabed mining may also become a threat as, although there are no mining contracts on the banks, there are several contracts for mining sulphides and nodules in the seabed in the surrounding region, the impacts of which have the potential to spill-over into the bank. In addition, oil tankers regularly traveling through neighbouring waters put its biodiversity at risk from oil spills and the dumping of waste.

These mounting threats make it imperative that this exceptional High Seas area is protected to safeguard biodiversity and boost its ecological resilience. In 2008, the bank was classified as an Ecologically or Biologically Important Area (EBIA) by the Convention on Biological Diversity. The Seychelles Plateau and Adjacent Oceanic Waters have been declared a potential Important Marine Mammal Area (IMMA), while the bank itself is a candidate Marine Important Bird and Biodiversity Area for white-tailed tropicbirds and wedge-tailed shear waters. Now there are international calls for the Saya de Malha Bank to be designated as a High Seas protected area, which could enable sustainable ecotourism, climate research, and ecological monitoring. As a biodiversity hotspot and key migration and breeding area, safeguarding the bank would help conserve marine life across the Indian Ocean basin.

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.  However, many are questioning the efficacy of the supposed safeguards in place. 

Encouragingly, 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 designating it as a High Seas marine protected area under the High Seas Treaty.

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