What is deep-sea mining, and why should we proceed cautiously?

This article was written for an ecology class and serves as a basic explainer on seabed mining.

On average, the ocean is just over two miles deep, but sunlight only penetrates about 700 feet below the surface—meaning the vast majority of the sea is characterized by total darkness, cold temperatures, and the crushing pressure of millions of pounds of water. These three factors—darkness, cold, and pressure—not only make it difficult to explore the bottom of the ocean but also create a harsh environment for the creatures that call this ecosystem home.

The organisms that live on the ocean floor tend to reproduce slowly, live for a long time, and have unique adaptations allowing them to live in these otherwise harsh environments. Without constant sunlight to stimulate primary production, most rely on nutrients that trickle down from the surface—dead whales, in particular, provide a boon to these ecosystems when creatures pick the bones of these fallen giants clean of their biotic mass. 

While most life relies on photosynthesis, which converts sunlight into energy, to fuel their cellular processes for primary production, the 1977 discovery of chemosynthetic organisms on the ocean floor by researchers at the Woods Hole Oceanographic Institution upended our understanding of life on Earth. These chemosynthetic organisms obtain energy from molecules typically containing carbon—a unique adaptation that allows hydrothermal vents on the ocean floor to support a habitat that receives no sunlight.

The presence of chemosynthetic organisms is just one unique feature of the ocean floor, about which we know less than we do about the surface of the moon or mars. After all, it’s much easier for modern sensing technology to sense light when it only needs to travel through the air, making it possible to observe the moon’s surface with a telescope or binoculars. Unfortunately, the same cannot be said for the ocean floor, where a lack of sunlight and the presence of particulate matter make such observations impossible.

Aside from sonar mapping, the best way to reach the ocean floor is with remotely operated vehicles (ROVs), which must be built to handle pressure several hundred times that on the surface. The high cost of developing and operating these ROVs limits exploration of the ocean floor to those seeking novel scientific discoveries—and those hoping to mine the seabed for its rich deposits of copper, cobalt, nickel, manganese, and other mineral resources.

Mining the seabed floor

Things accumulate slowly on the seafloor, and once they settle there, they stay there for a long time. And it’s not only biotic organisms, such as whales, and anthropogenic waste, such as plastic, that accumulates on the seafloor—vast stores of minerals have accumulated over millions of years, which international mining operations now seek to mine to meet the growing demand for batteries used to store renewable energy. 

Climate change is the world’s most pressing problem, and we must do everything we can to solve it immediately—or so the argument goes. The combustion of fossil fuels, which power everything from dishwashers in California to buses in China, emit greenhouse gasses that are warming our atmosphere. Therefore, we must find a different way of producing energy, and the two most popular eco-friendly alternatives are solar and wind—renewable resources that can provide virtually unlimited energy.

The problem is that this energy is only immediately available when it’s sunny or windy. So, if we get our electricity directly from the sun, how are we supposed to run our dishwashers at night? 

The solution is to capture renewable energy when it’s available and store it for later use. This requires high-powered batteries that use nickel, cobalt, and other minerals. Mining companies are exploring polymetallic sulfides, polymetallic nodules, and cobalt-rich crusts, which are located across the ocean floor, for deposits of the metals needed to mass-produce these batteries.

However, given how little we know about the deep sea, it is impossible to say how mining the seaflood for minerals will affect unique benthic ecosystems and organisms that call these places home. 

Oversight of seabed mining

The International Seabed Authority (ISA) was established in 1994 under the UN Convention on Law of the Sea “to organize, regulate and control all mineral-related activities in the international seabed area for the benefit of mankind as a whole.” In short, this international regulatory body is designed to ensure equitable access to deep-sea resources of and prevent any one nation from capitalizing on these resources, the demand for which, according to a recent LA Times article, could increase by 600% over the next few years.

Here’s how it works: if a private or government-backed entity wants to mine the seafloor, it must be sponsored by a member state of the ISA (of which the U.S. is not a party since it never signed the UNCLOS). So far, these member states have sponsored 22 contractors for 15-year exploration permits, including the Government of the Republic of Korea, China Ocean Mineral Resources Research and Development Association, and Nauru Ocean Resources Inc. To date, the ISA has yet to issue any extraction permits.

A look at exploration

What does exploration look like? For one, using sonar technology to map areas of the seafloor thought to be rich in these deep-sea minerals. Given that “less than 5% of the deep ocean has been seen by human eyes,” exploration entails identifying regions with high concentrations of mineral-rich regions. The area currently receiving the most attention is the Clarion-Clipperton Zone, roughly halfway between Hawaii and North America, which contains polymetallic nodules with nickel, manganese, copper, zinc, and cobalt. 

It also means using rudimentary technologies to extract samples of these minerals from the seabed. Current technologies include dropping a large, robotic claw miles to the seabed floor, clamping it shut, and bringing the finds to the surface; like an arcade game where the player attempts to grab a prize from behind a plexiglass window, this approach leaves much to chance. 

The previously mentioned LA times article quoted Sandor Mulsow, a marine geologist who formerly worked with the ISA, as likening it to “going into Central Park in New York with a soda straw, taking one sample and then trying to tell me how many worms are in all of the park.” 

How can mining affect the deep sea?

Environmentalists have raised several concerns about these methods, most of which relate to disturbing an ecosystem we know little about while not understanding how these actions will affect the seafloor and its surrounding ecosystems. After all, who knows whether another creature capable of upending our understanding of life on Earth is down there, just waiting to be discovered?

In addition to disturbing benthic ecosystems by leaving tracks on the seafloor, obtaining these mineral deposits requires bringing sediment to the surface and sifting through it. This sediment, which is often laden with toxic compounds after processing, is then discharged as slurry back into the ocean at the surface or at depth.

This is concerning for several reasons. The first is that we are disturbing a resource that took millions of years to settle in a single place, and there’s no telling what creatures inhabit this region and how they’ll be affected.

The second is that this slurry will not slink down to the same spot it was taken from—it will disperse throughout the water column, released throughout the ocean. This has significant consequences for the organisms that rely upon plankton and nutrients floating in the water as food sources. 

Much like smoke particles from a wildfire can block sunlight from reaching Earth’s surface, this slurry can prevent sunlight from reaching its normal depth—which has profound implications for the organisms that rely on photosynthesis to generate energy. Will they rise to the surface to better obtain light, concentrating in the ocean’s upper layer? Or will they be unable to cope with these changes and eventually die, only to sink to the bottom of the ocean? Either way, the discharge of this slurry is likely to have profound effects on open-ocean ecosystems/food chains that rely on these photosynthetic organisms for food, changes that will eventually make their way up the food chain and affect the fish that humans catch to eat.

The path forward

All this isn’t to say that we shouldn’t mine the deep sea—it’s that we shouldn’t proceed with mining the deep sea without a clear understanding of how it will impact benthic and open-water ecosystems. 

According to a recent study led by UC Santa Barbara researcher Diva Amon, “closing the scientific gaps related to deep-seabed mining is a monumental task that is essential to fulfilling the overarching obligation to prevent serious harm and ensure effective protection,” and should include “the definition of environmental goals and objectives, the establishment of an international research agenda to generate new deep-sea environmental, biological, and ecological information, and the synthesis of data that already exist.”

Climate change is an existential problem, and we must do everything we can to transition away from fossil fuel consumption. But that doesn’t mean we should fundamentally change one of the least disturbed ecosystems on Earth before we clearly understand how our actions will alter these ecosystems. 

We can only have a robust and informed public debate about mining the deep sea for minerals once we have a better understanding of these seabed habitats, the creatures that inhabit them, the role they play in the larger ecosystem, and how seabed mining will affect it all. 

References

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Woody, T., & Halper, E. (2022, April 19). A race to the bottom: In the rush to mine the ocean floor for minerals used in EV batteries, who is looking out for the environment? A gold rush in the deep sea raises questions about the authority charged with protecting it. Retrieved May 21, 2022, from https://www.latimes.com/politics/story/2022-04-19/gold-rush-in-the-deep-sea-raises-questions-about-international-seabed-authority