Deep Impact

Mapping the ocean floor could put undersea creatures at risk.


underwater photo of a jellyphoto NOAA OKEANOS EXPLORER ProgramA hydromedusa, seen just above the seafloor along the west wall of Mona Canyon.The deep sea is home to an astonishingly diverse menagerie of creatures. For every species that researchers have spotted, there are likely hundreds more that humans have yet to set their sights on.

Three kilometers below the ocean’s surface, the water is absolutely dark; sunlight does not penetrate to these depths. Extreme pressure and frigid temperatures are constants here. It is quiet, save for the occasional call of a distant whale. To say that these regions seem inhospitable is an understatement. And yet, they are teeming with life, home to an astonishingly diverse menagerie of creatures.

Dumbo octopuses undulate through the black depths, propelled through the cool waters by their ear-like fins. Delicate meat-eating sponges cling to sandy surfaces, capturing passing crustaceans with tiny hairs covered in microscopic hooks. Blind yeti crabs – so named for their furry yellow claws – scuttle across the sea floor, and tiny fish circle sulfur plumes. Bioluminescent sea worms provide glimpses of light in the pitch-black surroundings. These are just some of the stunning species that survive in the deep ocean, their features uniquely adapted to ensure survival. For every deep sea species that researchers have spotted, there are likely hundreds more that humans have yet to set their sights on. While geologists have charted mountain ranges and forests and desert tundras, and astronomers the heavens above, our planet’s oceans remain largely unexplored; it’s often said that we have a more complete understanding of the moon or Mars than we do of our own seabed.

The sea’s terrain in fact plays a critical role in our biosphere: Underwater crests and valleys determine weather patterns and ocean currents; sea topography influences the management of fisheries that feed millions, and miles of underwater cable that connect billions more to the Internet; seamounts provide protection against coastal hazards such as approaching hurricanes or tsunamis, and may even offer clues to the prehistoric movement of the earth’s southern continents.

We’ve spent relatively little time exploring the deep sea, and have only recently begun to discover its rich biotic life. But that biodiversity is already under threat. Last year an international team of experts from around the world, united under the nonprofit General Bathymetric Chart of the Oceans (GEBCO), launched the first effort to create a comprehensive map of the world’s oceans. Their goal? To make use of recent advances in sonar technology to expand our understanding of Earth’s most remote region. But the underwater discoveries that await aren’t only of interest to mapmakers and marine researchers. Far below the ocean’s surface, in fact as in fable, lies buried treasure: precious metals, rare earth elements, oil, and diamonds – riches that have so far remained inaccessible to even the most intrepid of prospectors.

While marine researchers are excited about the promise the mapping project holds for science, many fear that a map of our sea floor will enable extractive industries to profit from deep sea resources, endangering marine habitats and coastal communities in the process. They worry that a high-resolution map might plunge us into a realm once reserved for science fiction: roving robots, submarines, sea jewels, coral with pharmaceutical properties, Wild West maritime law, toxic sediment plumes. Once the map is made, will it be used as a tool for responsible management and conservation, or wielded like pirate’s treasure map, a guidebook to extraction and exploitation?

Only about 5 to 15 percent of the earth’s ocean has been mapped in detail. Zoom in on the middle of the Pacific in Google Earth, for example, and you’ll find a representation of the ocean floor based on satellite- and gravity-derived bathymetry: low resolution and often inaccurate. Considering that we’ve plotted our solar system and charted the human genome, it’s rather astonishing that no comprehensive high-resolution map of the seafloor exists. But the reason is simple: Our planet’s oceans are vast, deep, and largely impenetrable, and water literally gets in the way of our explorations.

For centuries, charting the ocean depths meant braving the high seas, dangling plumb lines – ropes weighted at one end – over the side of a ship, then drawing basic contours on cartographic maps. Sailors etched soundings onto maps as early as the sixteenth century, but no international standards for terminology or scale existed then, meaning early maps were not only rudimentary wayfaring tools, they were also often confusing and contradictory. It wasn’t until the turn of the twentieth century, an era marked by soaring interest in the natural world, that a group of geographers gathered under the leadership of Prince Albert I of Monaco to produce the first international charts of the ocean. (This mapping project would eventually become GEBCO.) Nicknamed the “Prince of the Seas,” Albert was fascinated by the then relatively new science of oceanography, and commissioned four research yachts to survey the Mediterranean. In 2017, more than 100 years later, GEBCO and the Nippon Foundation formally announced Seabed 2030, an intergovernmental project that aims to map the entire sea floor in high resolution by the year 2030.

Technological advances since Prince Albert I’s time make this goal attainable, if very ambitious. Modern ships like the kind used in Seabed 2030 are now outfitted with multibeam bathymetry, sonar systems that emit sound waves in a fan shape beneath a ship’s hull. Each sonar ping in the “fan” measures the time it takes for a signal to reach the seafloor and return to the surface, a calculation of the water’s depth that can be marked as a coordinate on a grid.

The deep sea is estimated to hold many riches, including rare earth minerals.

“Multibeam extends the map area and gives us extended coverage,” explains Dr. Vicki Ferrini, chair of GEBCO’s subcommittee for undersea mapping. Most ships already rely on sonar for obstacle avoidance and navigation but their sonar mapping devices can map only their underwater footprint – the strip of the sea floor directly under the ship. Vessels with multibeam sonar systems have dramatically increased the area of seafloor that researchers can ensonify – that is, capture with sonar. “The process is a little like mowing a lawn with a riding mower versus a push mower,” Ferrini explains.

Still, piecing together a comprehensive map remains a challenge. Ocean shipping routes are a lot like highways: Certain parts of our oceans are heavily trafficked, while others may have no roads at all. Popular routes will be easier to map: GEBCO hopes to encourage cargo ships, fishing boats, and pleasure craft to participate in the project and transmit their data in real time, effectively crowdsourcing large portions of the underwater map. While research vessels are more likely to feature sophisticated equipment, many ships are already equipped with basic sonar devices for their own navigational purposes. Given the ocean’s size, harnessing any data helps researchers to fill in the gaps, as it were.

Because continent-sized swaths of our planet’s seas are not regularly cruised by ships, Seabed 2030 also hopes to inspire new mapping expeditions that target out-of-the-way sections of the ocean, and to encourage mining companies to contribute bathymetric data garnered during prospecting activities. As Dr. Ferrini explains, oil, mineral, and seismic companies might elect to contribute decimated, or lower resolution data, to GEBCO’s map, thereby protecting their commercial interests while adding important information to the 2030 project.

Sonar data is valuable “particularly in areas where we don’t have anything,” says Rear Admiral Shepard Smith, director of the US Office of Coast Survey at the National Oceanic and Atmospheric Administration, another contributor to Seabed 2030. In poorly mapped areas of the Pacific or the Arctic, for example, sonar data from non-research ships can be quite helpful, he says.

Perhaps no single modern expedition reveals the complexity of deep sea ocean mapping more strikingly than the search for the still-missing Malaysian aircraft MH370 and its 239 passengers and crew. Investigators suspect that the plane, which vanished in 2014 en route from Kuala Lumpur to Beijing, had crashed in a remote area of the Indian Ocean. The area was so poorly mapped, however, that search teams had to do basic mapping of the area before they could draw up a more precise map with enough resolution to spot wreckage. In fact, with an estimated depth of some 4,500 meters, the search area was too deep to explore with ship-based sonar. Instead, investigators dispatched a fleet of autonomous underwater vehicles, or AUVs, which can descend below the ocean surface and use cameras and sonar to map areas that ship-based sonar can’t reach.

aerial photo of a ship, with a crane lowering a submersiblephoto NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011NOAA’s Okeanos Explorer uses robotic submarines to explore deep sea vents. In the future, autonomous surface and underwater vehicles might eliminate humans from the at-sea aspects of exploration and mapping.

Though underwater robotics is in its infancy, deep sea surveys have come to rely increasingly on these robotic submarines for more detailed mapping. “There are many advantages to AUVs,” explains Dr. James Bellingham, director of the Woods Hole Center for Marine Robotics in Massachusetts. “They are faster, they provide higher-resolution seafloor surveys, including hazard assessment, they lower upfront capital costs, and provide increased access to the ocean.”

Researchers are currently designing new AUV models that can be launched from land, and that need no oxygen to combust (they rely instead on battery power). Of course, these assets can quickly turn into hazards: Batteries need to be recharged, navigation systems must be tracked from nearby ships, and an AUV that breaks down must be brought back to port for service. “In the future,” says Bellingham, “an autonomous surface vehicle might tow out underwater vehicles,” thus eliminating humans from the at-sea aspects of mapping altogether.

As the technology continues to develop, AUVs will likely play a significant role in the Seabed 2030 project. They may offer the best chance of mapping the deepest reaches of the deep sea, nearly 11,000 meters below the ocean surface.

The Indian Ocean is known in Sanskrit as Ratnakara, “the mine of gems.” The name is indeed prophetic: hidden in the subsea mountains and valleys of that remote ocean are pools of resources, including rare metal alloys, sulfur, even diamonds. Thousands of kilometers from the Indian Ocean lies the Clarion-Clipperton Fracture Zone, a vast stretch of water southeast of Hawaiʻi that extends to Mexico. If Ratnakara is the mine of gems, Clarion-Clipperton might be the Yukon of deep sea mining: a Wild West frontier full of promise. Prospectors believe this remote patch of the Pacific holds everything from manganese and diamonds to nickel and cobalt. Most prospecting is currently focused in the Indian Ocean and Clarion-Clipperton Fracture zone, but underwater riches could lie in wait of discovery in countless other regions, perhaps in higher quantities than in many land-based mines. In total, experts estimate that seafloor deposits contain from 600 million to 1 billion tons of minerals.

In the absence of a detailed map of the sea floor, however, it’s difficult to confirm whether these resources actually exist. Few detailed site surveys pinpoint their location, though some have been made. More often, estimates are based on knowledge of geologic processes that create these minerals.

Currently, prospectors target three types of formations. Hydrothermal vents – fissures in the planet’s surface that release geothermally heated water – are known for their deposits of gold, silver, and zinc. Below the ocean surface, hot water dissolves minerals in surrounding rocks, creating a chemical-rich broth that can reach up to 750 degrees Fahrenheit; as warm fluids emerge from the vents, they encounter cold water, which forces metal sulfides in the mixture to form solid deposits near the seafloor. Prospectors also seek out cobalt crusts found along the sides of underwater volcanoes or seamounts, which are rich in manganese and nickel, as well as cobalt. Then there are polymetallic nodules, which form over millions of years as dissolved metals in ocean water settle around a nucleus of some sort – a piece of shell, for example. Such nodules are rich in copper, cobalt, nickel, and manganese.

These aquatic deposits are already on commercial radar. Of special interest are rare earth minerals: metals used in everything from cell phones and DVDs to rechargeable batteries, magnets, computer memory chips, and fluorescent lighting. Most modern technology relies on these minerals, which are not readily found in economically exploitable ore deposits. Currently, China produces more than 85 percent of the world’s rare earth supply, a market monopoly that many countries are eager to break. Deep sea mining companies are betting that their investments will ultimately pay off.

One such company, Nautilus Minerals, hopes to launch what is considered the world’s first deep sea mining operation as early as this year. Using existing technologies adapted from the offshore oil and gas industry, Nautilus is developing a production system to extract high grade copper, zinc, and silver from the seafloor in the territorial waters of Tonga and Papua New Guinea, a proposal that has proved highly controversial with local communities. Another, De Beers Group, a household name in diamond mining and retail, formed a partnership with the Namibian government more than 20 years ago in pursuit of diamonds off the coast of that mineral-rich country. More recently, De Beers added to its naval fleet several AUVs – part of a drill and crawler mining system that can scour the surface of the seafloor, loosen deep seabed sediment for rough diamonds, and haul the cache more than 100 meters to the surface.

While shallow-water mining for sand, gold, tin, and diamonds is a decades-old enterprise, commercial deep sea mining is a new industry, its environmental impact yet unknown.

Based on what we know of current ocean mining proposals, scientists predict significant and lasting effects. Existing proposals for deep sea mining involve trawler- and vacuum-like equipment that scoop up seafloor deposits and lift them thousands of meters from the ocean bottom to a ship via a suction pump. From there, companies load mineral-rich rocks onto cargo ships for transport to processing plants. Potential consequences include habitat degradation, sedimentation, toxic plumes from surface ore, undersea noise that disturbs ocean life, and spills during transport, all of which could contribute to species extinction.

As scientists begin to understand the geological, chemical, and biological forces that conspire to create deep sea mineral deposits, one thing is clear: These unique forces spur not only accumulation of precious resources, but also lush communities of sea life.

photo of a deep-ocean thermal ventphoto Charles Fisher/Pennsylvania State University / Woods Hole Oceanographic InstituteHydrothermal vents are known for their deposits of gold, silver, and zinc. They are also known to support diverse ecosystems teeming with life.

Take the Clarion Clipperton Zone, the focus of much ocean prospecting: A 2016 study published in Scientific Reports detailed an impressively biodiverse ecosystem there. “The biggest surprises of this study were the high diversity, the large numbers of new species, and the fact that more than half of the species seen rely on the nodules – the very part of the habitat that will be removed during the mining process,” Diva Amon, the lead author and a post-doctoral researcher at the University of Hawaiʻi at Manoa, said in a statement.

In general, abyssal ecosystems – ecosystems between roughly 3,000 and 6,000 meters below the ocean’s surface, where most nodules are found – are highly vulnerable. At these depths, conditions are relatively stable, and any disturbance could have an outsized impact. “Although the full consequences of deep sea mining on abyssal ecosystems aren’t fully known, environmental impacts could be disastrous and irreversible,” says Dr. Abel Valdivia, a marine ecologist at the Center for Biological Diversity, an environmental group. Sediments can quickly clog gills of species not adapted to murky waters. “Because these deep sea ecosystems rely on chemical synthesis rather than photosynthesis to survive,” says Valdivia, “any changes in the chemical environment could drastically affect ecosystem functioning and lead to mass mortalities of basal species.”

Or consider deep sea hydrothermal vents. Underwater vents support highly diverse marine populations: crabs, mussels, sponges, fish, and giant worms all make their homes in this habitat. “We’re up to nearly 1,700 new species at hot vents – nearly 90 percent of them have not been seen anywhere else,” Verena Tunnicliffe, a marine scientist at the University of Victoria in Canada, said during a presentation at an international seabed management conference last year.

A De Beers spokesperson says that the company “does not mine in areas considered to have high diversity of marine life,” explaining that, post-mining, “seabed recovery occurs naturally over a period of time and is assisted by the sediment that we return to the seabed.” Nautilus states on its website that the company’s operations will “minimize environmental impact.”

But an international group of 15 marine scientists insists that environmental impacts simply cannot be adequately minimized in these delicate ecosystems. “Loss of biodiversity will be unavoidable because mining directly destroys habitat and indirectly degrades large volumes of the water column and areas of the seabed due to the generation of sediment plumes that are enriched in bioavailable metals,” they wrote in a letter published in Nature Geoscience last year. “Most mining-induced loss of biodiversity in the deep sea is likely to last forever [emphasis added] on human timescales, given the very slow natural rates of recovery in affected ecosystems.”

A fledgling deep sea mining industry still faces a host of challenges, as conservationists, lobbyists, scientists, and local residents put up roadblocks to deep sea drilling. Communities in Papua New Guinea, for example, have challenged the mining proposal off their shore, and in 2015 the Center for Biological Diversity sued the US government for granting mining exploration permits in the Clarion-Clipperton zone. Several environmental groups, including the Center for Biological Diversity, are campaigning against deep sea mining. But the framework for evaluating mining disputes has yet to be finalized, meaning that sea-exploration enforcement efforts remain as murky as the oceans they are meant to govern. The United Nations Convention for the Law of the Sea is the legal framework that, in 1982, first set out the rights and duties of countries with respect to the use of ocean resources. The law states that deep sea life must be protected, and that revenue made from any mining venture there must be shared with the international community.

The International Seabed Authority (ISA), a Jamaica-based regulatory body created under the auspices of the convention, is the institution that actually regulates deep sea mining in international waters. The ISA grants mining permits, offers recommendations on technology and best practices, and issues mining codes that restrict deep sea prospecting. So far, the ISA has issued 27 permits for deep sea mineral exploration – given to company-country pairs that have teamed up for exploration efforts in international waters – though the organization has not yet issued any for extraction. The ISA is expected to finalize environmental regulations governing deep sea mining later this year. It’s unclear how these regulations – which will not apply to nations’ territorial waters – will balance environmental concerns with economic interests.

“How do you assess environmental harm in an area of great scientific uncertainty?” asks H. Jordan Diamond, a lawyer and the executive director of the Center for Law, Energy & the Environment at the University of California at Berkeley. Another, more pressing question might be: What will happen to that area if the plundering of its natural resources is left unchecked?

Scientists are working to learn as much about the deep sea as they can before exploitation mushrooms. This effort stems from scientific curiosity, but also the need to better understand deep sea ecosystems in order to effectively evaluate – and mitigate – our impacts on them. “This is a race,” says Bellingham, the director of Woods Hole Center for Marine Robotics. “A race to get a baseline understanding of our ocean before we change it dramatically. We’ve lost that race already in the Arctic – life that used to live in sea ice no longer survives.”

Once detailed bathymetric information is made available to the public, protective measures must be taken to safeguard the landscape it describes. “A map is an investment in responsible management of the seabed in the coming centuries,” says Rear Admiral Smith. Indeed, we have but one planetary ocean, and its preservation depends on conscientious stewardship – particularly as we turn to its depths for the resources we can no longer find on dry land.

You Make Our Work Possible

You Make Our Work Possible

We don’t have a paywall because, as a nonprofit publication, our mission is to inform, educate and inspire action to protect our living world. Which is why we rely on readers like you for support. If you believe in the work we do, please consider making a tax-deductible year-end donation to our Green Journalism Fund.

Get the Journal in your inbox.
Sign up for our weekly newsletter.

Subscribe Now

Get four issues of the magazine at the discounted rate of $20.