Bycatch from a bottom trawler off the coast of Sète, France, March 2021. Photo by Maxime Gruss/Hans Lucas


Defend the deep

Instead of letting waves of exploitation sweep through the deep ocean, we could choose to protect this vast living realm

by Helen Scales + BIO

Bycatch from a bottom trawler off the coast of Sète, France, March 2021. Photo by Maxime Gruss/Hans Lucas

‘Speak, thou vast and venerable head … Of all divers, thou hast dived the deepest. That head upon which the upper sun now gleams, has moved amid this world’s foundations.’ So says Captain Ahab as he peers over the side of his whaling ship, Pequod, at the head of a sperm whale.

Herman Melville would have been astounded to know what sperm whales encounter as they hunt in the deep sea. When Moby Dick (1851) was published, the scientific establishment still generally held the view that below the upper 300 fathoms (around 550 metres) the ocean was empty of life. In truth, the deep is not only a ghoulish realm of shipwreck and pirate victims, as Melville imagined, it’s home to a tremendous panoply of strange animals. Sperm whales dive well past the 200-metre mark – the official beginning of the deep – to at least 2,000 metres. As they chase after enormous squid, sperm whales pass so many lifeforms unlike anything on land.

The rules of life are very different in this pitch-dark, chilled, high-pressure environment, leading evolution down different paths. There are intricate, jelly-based creatures illuminated by their own twinkling lights, and gossamer worms spinning in tight, twirling circles. There are fish that look like sock puppets, their mouths unfolding to preposterous proportions to swallow whatever prey comes by. Bone-eating worms with red tufted gills and plant-like roots await the bodies of sunken dead whales and their stripped-back bones, after the scavenging crabs, sharks and snails have taken turns at the feast that falls from above.

Life in the deep goes far beyond the reach of sperm whales – all the way to the very bottom of the sea in fact. Tumbling down from the edges of continental shelves in every named ocean, the deep has an average depth of around 4 km and drops into trenches almost 11 km deep. In total, the deep ocean is roughly 1 billion cubic km in size and makes up roughly 95 per cent of the available living space on Earth. It’s tempting to assume the deep is too big and too remote for humans to impact in any meaningful way, and for all forms of deep-sea exploitation to be insignificant on a planetary scale. But those assumptions are simply wrong.

Hunting for sperm whales, from Melville’s time into the 20th century, was the first global industry to exploit the deep ocean. Sperm whales are air breathers but in truth they’re denizens of the deep that spend three-quarters of their lives hundreds of metres underwater. In the 20th century alone, at least 760,000 sperm whales were slaughtered, more than twice the number thought to exist today. The loss of so many whales was a catastrophe for the species and also altered the functioning of the planet. Sperm whales are one of many living elements of the global carbon pump that draws carbon dioxide out of the atmosphere and stores it in the deep ocean for millennia. During brief rests at the surface between dives, sperm whales defecate and fertilise blooms of carbon-fixing phytoplankton. Some of these minute algae die and sink into the abyss, clumped in particles known as marine ‘snow’ and taking carbon with them. Before industrial whaling, sperm whales removed millions of tonnes of carbon from the atmosphere each year, a service to climate regulation that has become drastically diminished.

The whale massacre did, however, come to an end before all the whales were gone. In 1986, a moratorium banned the commercial hunt for all the great whales, including sperm whales. Within a few short years, whales were no longer an industrial resource to be exploited but cherished wildlife deemed worthy of protection.

The history of whaling is a stark warning of the damage people can cause to the living world. Perhaps more importantly, it’s a rare reminder that we humans can change our minds over what is important and worth looking after, even in most distant, unseen places such as the deep ocean. We’ve done it before, and we now need to do it again.

The deep is under grave threat today from three different and often related human activities: fishing, pollution and mining. Unless action is taken swiftly, it will be too late to stop serious damage to species, habitats and the health of the entire global ocean.

Instead of letting these waves of exploitation sweep through the deep, humanity could decide to protect this vast living realm. Agreements could be drawn up that declare the deep ocean off limits to extractive and exploitative industries. Such a move would halt existing damaging activities before they cause any more trouble, and prevent the newest threats from taking hold. And there are clear, logical motivations for doing so.

For millennia, people have gathered food from the edges of the ocean and shallow seas. More recently, the search for seafood has been sinking deeper, as more accessible waters became overfished and overcrowded with fishing fleets competing for space and catches. As fishers have lowered nets further down, the deep has shown itself to be extremely sensitive to disturbance and woefully slow to recover from damage and depletion.

In the mid- to late 20th century, trawlers in the Pacific began operating over giant underwater volcanoes known as seamounts whose peaks don’t reach the surface. A major target was the orange roughy, a palatable, white-fleshed fish that has become a classic example of why deep-sea fishing is a terrible idea for the environment. Catches from seamounts off New Zealand and Australia were huge, at first, when trawlers could extract as much as 50 tonnes of fish in a single shot. Roughy catches boomed and then all-too quickly collapsed. When that happened, the trawl fisheries simply pulled up their nets and motored on to the next seamount.

It soon became apparent that trawling would not only rapidly deplete orange roughy but also demolish fragile, mountain-side habitats. Underwater forests grow on seamounts, built by intricate, plant-like corals and sponges that can live for hundreds and even thousands of years. Fish, octopuses, starfish, sea urchins and countless other species depend on these habitats. Trawlers would haul up tonnes of corals in their nets, but only for a short time before almost all the tree-like animals were felled and gone. Studies comparing trawled to un-trawled mounts show few signs of the coral and sponge habitats recovering, decades after the trawlers have moved on.

Those fish are doing the ocean and the whole planet a great service as they go about their restless lives

Orange roughy are also taking a long time to recover. It’s no great surprise, given that an individual roughy can live for 250 years, and they don’t reach sexual maturity until they’re 20 to 40 years old. Somewhere out there should be shoals of adolescent roughies produced by the previous generation before so many were wiped out. By now, they should be swimming to seamounts to spawn in great aggregations, but so far hardly any are showing up. Where the rest are and if they exist at all is a worrying mystery.

Currently, not a great deal of orange roughy fishing goes on, but deep-sea fisheries continue to exploit other animals that can live to an immense age. Deep-dwelling sharks are targeted for their oily livers as a source of the cosmetic and vaccine additive squalene. The sharks have little innate resilience to exploitation and very low capacity to replenish their diminished populations. Female gulper sharks, for instance, are pregnant for two years before giving birth to a single pup. A 2021 assessment revealed that one in three species of sharks and rays are now threatened with extinction, including many from the deep sea that are being overfished.

Plans for a new kind of deep-sea trawl fishery would likely bring a different kind of ecological damage, not to seabed habitats nor to long-lived species, but potentially to the global climate. Trillions of small fish that look like glittering, big-eyed sardines, inhabit the twilight zone between 200 and 1,000 metres down. Collectively, these lanternfish and bristlemouths are the world’s most abundant vertebrates, and to many industrialists their unexploited biomass is simply going to waste. These fish are too bony for people to eat, but there could be money to make mashing them into fishmeal for livestock feed or Omega-3 additives for health food supplements and pet food.

Trouble is, those fish are doing the ocean and the whole planet a great service as they go about their restless lives. Each night, they rush to the surface to feed in the shallows under the cover of darkness before cascading back down again at dawn. On their descent, the fish bring with them bellies-full of organic matter and drag huge amounts of carbon away from the atmosphere into the deep. Twilight zone fisheries, if they were to commence, could disconnect these billions of critical connections between the surface and the deep, causing an alarming carbon toll.

Exploiting the deep ocean doesn’t just involve extracting resources; it’s also about throwing things into this apparently endless space. In times gone by, it’s been easy enough to assume that the enormous deep could swallow any pollutants and trash dumped in, with no damage done to people or the planet. This was the premise of 20th-century military operations of various countries that used the deep as a dumpsite for toxic waste. At least 1 million tonnes of unused and decaying chemical weapons were thrown into the deep, in an effort to put them out of harm’s way. Huge quantities of mustard gas, sarin, VX and other nerve agents have been poured into barrels and pushed off the side of ships, or entire ships were loaded up and scuttled. Civilian wastes have also been dumped in the deep. For decades, up until 1992, untreated human sewage was routinely loaded into ships and tipped into the sea off the coast of New York, first in New York Harbour then later at a deeper site 106 miles offshore. In the 1970s, thousands of tonnes of pharmaceuticals-laced waste was dumped into the four-mile-deep Puerto Rico Trench.

The location of most deep-water dumpsites remains unknown. Recently, scientists stumbled across one off the coast of Los Angeles. The team went back and, using autonomous, deep-diving robots and sonar scanners hooked up to powerful computer algorithms, they identified more than 27,000 barrels lying on the seabed in neat lines, presumably from where ships motored along and pushed them off the back. The barrels are thought to be full of the dangerously toxic pesticide DDT. Next comes the challenge of working out the ecological impact of the dumpsite, and deciding what to do about it. Options include attempting to retrieve the toxic barrels and finding somewhere else to put them, or encasing them in concrete where they lie.

Deliberate dumping of toxic wastes in the deep sea was outlawed by the London Convention in 1975, another sign that people can wake up to their shameful misuse of the ocean and decide enough is enough. However, intentional disposal has now been replaced by the kinds of insidious, accidental pollutants that are getting everywhere. Persistent industrial chemicals linger dangerously in ecosystems, and plastics are sinking to the greatest depths. And as more oil platforms are installed in ultra-deep waters (1,500 metres and more), it becomes likely that more catastrophic oil spills will occur, like the Deepwater Horizon spill in 2010.

Snails with iron shells, giant tube worms as tall as a human adult and clams the size of dinner plates would be lost

Especially worrying for the future of the deep sea are plans to start mining minerals from the seabed. Mining companies hoping to begin this controversial new industry are prospecting metal-rich rocks, known as nodules, that lie scattered across the abyss. Resembling knobbly lumps of coal, the nodules grow from minerals settling out of seawater, taking 10 million years to expand from the size of a pea to a golf ball. Aspiring deep-sea miners from dozens of countries are clamouring to prospect a Europe-sized portion of the central Pacific Ocean, called the Clarion-Clipperton Zone, and get their hands on the cobalt, nickel and other elements inside the nodules. Elsewhere, miners want to exploit metallic crusts on seamounts and the black smoker chimneys of hydrothermal vents, which form their own unique oases of deep life.

Mining companies claim that deep-sea mining will offer the greenest option to obtain metals for building solar panels, wind turbines and electric vehicle batteries. It will, they say, cause less environmental damage than land-based mining. But that’s assuming there’s little else of importance living in these deep waters – which is simply not true.

Sending down remote-operated bulldozers and drilling robots would destroy unique species and remove habitats that won’t recover on human timescales. Snails with iron shells, giant tube worms as tall as a human adult, ghostly white octopuses, fish, crabs, clams the size of dinner plates and much more would be lost. Each nodule mine would exploit hundreds of square kilometres of the abyss each year, with plans to operate non-stop for decades. Clouds of choking, toxic sediments would drift far from the mined sites, into waters where tuna, turtles, whales and whale sharks roam.

Seabed mining also threatens to disrupt processes that regulate the climate. Mining abyssal nodules could interfere with carbon stores in the deep seabed where flurries of marine snow accumulate. What’s more, after nodules have been extracted and pumped to the surface, waste seawater laden with sediments and heavy metals would be pumped back down creating a new kind of deep-sea pollution. Gritty plumes injected into deep midwaters would clog and choke jellyfish and other delicate, gelatinous animals that play a major role in the drawdown of carbon into the deep.

Much is still to be understood about how mining, pollution and fishing impact life in the deep and how these activities threaten the health of our planet. Already, though, enough is known to warn against opening up this last, vast frontier to unfettered industrial exploitation. Time and again, humanity has stumbled through the same old story of resource use: explore, exploit, deplete, then move on and repeat. We could instead tread a path of utmost caution and do whatever possible to safeguard one of the few remaining, relatively unspoiled parts of the planet. How, then, do we go about protecting the deep?

Realistically, it will need to happen on a sectoral basis, seeing as many players are already involved in exploiting swathes of the deep ocean.

Regulating fisheries in the deep currently falls to regional fisheries management organisations (RFMOs) that are in charge of specific geographical regions of the high seas, areas far from land, beyond national boundaries, where most of the deep sea lies. A decade ago, there were virtually no restrictions on trawling in the high seas. Now, roughly three-quarters of known seamounts at fishable depths, between 1,500 and 2,000 metres, have either been officially closed by the relevant RFMOs or put provisionally off limits. Nevertheless, bottom trawling continues on many of the remaining unprotected seamounts. The exact number is unknown but in total there are hundreds of thousands of seamounts worldwide. As of 2018, six nations were operating approximately 20 vessels, in particular New Zealand trawlers in the South West Pacific. Together, seamount trawlers target four main fish species, all of which are exploited at unsustainable levels, and cause huge ecological damage to fragile ecosystems that will take decades or longer to recover.

The RFMOs, and the states that are party to them, could decide to protect all high-seas seamounts from bottom trawling. This would be an important step towards implementing a resolution adopted at the United Nations General Assembly back in 2004, which committed states and RFMOs to take urgent action to protect vulnerable marine ecosystems from destructive fishing, seamounts included.

The ISA could do the same for deep-sea mining as the IWC did for whaling

Other parts of the deep are also being trawled globally, and here too there has been some progress in protecting vulnerable species. In 2016, the EU adopted a ban on trawling deeper than 800 metres, and since then catches including orange roughy and deep-sea sharks have dropped. However, EU states are not doing such a good job of implementing another part of this agreement, which pledged to stop trawling below 400 metres on vulnerable ecosystems. These restrictions need to be put fully into place and similar agreements rolled out into other national waters via governments and RFMOs across the high seas.

Regulating fishing activities and enforcing regulations far from the horizon is a challenge that technologies are beginning to solve. Satellite-based monitoring systems can now track vessels and identify what they’re up to, based on their movements. These tools will no doubt be put to use when UN negotiations conclude on a new treaty for the high seas. Depending on the final outcome, this should make it easier to establish protected areas and to outlaw damaging fishing in the high seas, including deep-sea fisheries of the future.

Unlike open waters of the high seas, the deep seabed already has an overarching organisation charged with its upkeep. The International Seabed Authority (ISA) was set up in 1994 by the UN to facilitate the development of the deep-sea mining industry and to ensure no environmental harm is done. The ISA has a similar dual remit as the International Whaling Commission, the body that took seriously the grave concerns over the industry’s impacts on whale populations and introduced a moratorium. The ISA could do the same for deep-sea mining.

Dozens of mining companies have paid the ISA for prospecting licences to explore vast portions of the seabed. The ISA should release mining permits only once a set of regulations is finalised, which among other things need to ensure that mining doesn’t cause serious environmental harm. Major sticking points include whether such precautions will be taken, how they would be enforced, and if they’re even possible. Much more time is needed to work through those regulations and to conduct sound science to inform them. In June 2021, however, the government of Nauru, which works closely with the Canadian corporation the Metals Company, triggered a legal clause that could see them mining in as little as two years, no matter what regulations are in place by then.

But this is not a done deal. Nauru’s application – and any others that might follow from countries that want to start mining including the UK, France, Japan, China and Russia – could still be turned down by the ISA.

Even before this recent bullying pressure on the industry, momentum has been growing for a moratorium on seabed mining, a pause in the industry of at least 10 years that would give scientists time to properly assess its impacts. Most recently, in September 2021, governments and civil society groups at the World Conservation Congress voted overwhelmingly in support of a deep-sea mining moratorium. This sends a clear message to the ISA that there is strong global opposition to deep-sea mines opening any time soon.

It’s well within the power of the ISA to withhold mining permits and impose a moratorium. However, because of the way the ISA is set up, a vote could easily be blocked by member states that have interests in seabed mining.

In order to understand and know life on Earth, we have to look into the deep and look after it

That’s why discussions need to continue beyond the ISA in forums where the international community takes a full and active role. A good option is the UN General Assembly in New York, a global body with universal membership that gives equal voice to all states. A promising next step for a moratorium is a UN resolution, such as the one that in 1989 outlawed high-seas drift netting, an ecologically disastrous fishing method. A resolution on seabed mining could also encompass a wider strategy for a more ethical and sustainable metals supply. What’s needed is a closed-loop materials economy, reduced demand for primary metals and far cleaner, more responsible mining on land – all things the UN can push for.

There are so many good reasons to protect the deep. Take your pick from climate regulation and preserving biodiversity, or from the chemical inspirations for new medicines, or the immense ideas that the deep brings us of life and how it operates. Living cells might have first emerged on deep-sea hydrothermal vents. If we lose those, we might lose clues as to how this whole living planet of ours got going. In order to understand and know life on Earth, we have to look into the deep and look after it. Exploiting this vast living space, we run the risk of losing species and habitats before we find them, and we could unravel this interconnected web of life before truly comprehending how much it matters to us all.

There’s no shying away from the overwhelming scale of the task of fully protecting the deep, but there is an uplifting precedent. This year sees the 60th anniversary of the Antarctic Treaty coming into force. An original set of 12 signatories, since joined by dozens more states, have given up their territorial claims to the frozen southern continent, and agreed that Antarctica should be a place devoted to peace and science.

It would be an enlightened act if humanity were able to gather together and decide that there are other places as fragile and important as Antarctica, places that likewise need to be set aside and left alone – for all our sakes – and that one of those places is the deep.