What Deep-Sea Mining Means for Terrestrial & Aquatic Environments
Introduction:
For decades, the environmental consequences caused by land-based mines have been widely studied and reported, as whole ecosystems are wiped due to the destruction of forestland that hosts an innumerable number of species causing a huge plummet in biodiversity, while also polluting the land around us. The human cost is bleak too, children and families having to work in mines, risking their lives for mere cents per hour.
While mining on land can be done responsibly, the consequences when it’s not are catastrophic—and far too common.
As demand for critical minerals continues to rise, there is no longer the choice between whether mining and not mining is the proper way forward, rather it is about we mine the ocean. Land-based extraction carries severe ecological and human burdens; yet deep-sea deposits may offer a lower-impact supply route, but only if development is led by ecological research, conservative engineering, and strict oversight as deep-sea mining could preserve life both above and below the waves
1.0: What Does Deep-Sea Mining Mean for the Environment Above
The intertwined crises of pollution, climate change, and human suffering are only now being fully recognized, and mining plays a role in all three.
Soil & Water Contamination: Heavy metals like lead and mercury leach into soil and water through rainfall or dust fallout. Acid drainage lowers pH levels in rivers and aquifers, killing microbes, breaking down nutrient cycles, and rendering land infertile for decades. These toxins move through the food chain, increasing cancer, organ damage, and neurological disorders in nearby communities.
Air Pollution: Dust from mineral extraction and toxic vapors from smelting release lead, arsenic, and mercury into the air—causing respiratory illnesses, lung cancer, and neurological issues. Acid rain from these pollutants devastates vegetation and acidifies lakes and soil, often far from the mine itself.
Habitat: Mining operations destroy vast habitats through deforestation and excavation. When soil microbes die, the entire nutrient cycle collapses, taking ecosystems down with it.
Health Consequences: Toxic metals don’t just harm ecosystems—they poison people. Contaminated food and water raise risks for cancers and neurological decline.
Beyond these local effects, terrestrial mining produces a staggering carbon footprint—an estimated 6–8% of global greenhouse gas emissions [1]. Mining for fossil fuels worsens the picture: responsible for roughly 68% of global greenhouse gases and 90% of CO₂ [2] emissions, it accelerates global warming and mass species loss.
The human toll was touched on briefly earlier, but the true depth of it is staggering. In the Democratic Republic of the Congo—where much of the world’s cobalt originates—miners earn just $1–10 per day. Reports from both the ILO and UNICEF have continuously documented hazardous child labor conditions on artisanal cobalt mines [3]. Land-based mines host a plethora of problems, yet it still remains our only source for new metal acquisition. The message is clear, this cannot remain our only method to acquire the resources that will forward us to a cleaner and green future. Deep-sea mining could provide a better path.
2.0: The Benefits of Deep-Sea Mining
Unlike terrestrial mines, deep-sea mining— for polymetallic nodules—requires no drilling, tunneling, or soil removal.
It is important to note that the ocean acts as a carbon sink, and Initial rough estimates predict 175 t C/km2/ yr will be released (t = tonnes) [4]. Yet that number only represents the amount of carbon released, not CO2 released.
If we assume that current estimates are correct and that:
3,000,000 t of nodules will be extracted from the seafloor annually over a 200km2 area.
Average nodule metal content: ~1.3% Ni, 1.1% Cu, 0.2% Co, 28% Mn
Table 1. Estimated carbon emissions intensity for polymetallic nodule extraction compared with conventional land-based mining. Deep-sea estimate assumes ~633 t CO₂ released per km² of sediment disturbance per year [4] and ~770 t of retrievable metal content per km². Land-based mining emissions range derived from lifecycle analyses reported in [8].
| Source/Method | Estimated emissions | Basis of estimate | Approx. CO2 per ton of metal |
|---|---|---|---|
| Deep-sea polymetallic nodule extraction |
633 t CO2 per km2 of seabed disturbed/yr |
Carbon disturbance estimate from abyssal sediment studies |
0.8 t CO2 / t metal |
| Land-based cobalt/copper/nickel mines |
2-20 t CO2/t metal | Lifecycle assessments of industrial refining processes |
2-20 t CO2 / t metal |
Even factoring in vessel operations and ore transport, deep-sea mining’s total footprint may remain far smaller—especially with green technologies powering the supply chain. Equally important, deep-sea mining reduces the human cost. It eliminates the need for dangerous manual labor, cutting the risk of death, disease, and exploitation. Still, the environmental risks below the surface cannot be ignored.
3.0: The Possible Consequences
3.1: Why Nodules Matter for Benthic Communities
Deep-sea mining possibly has the ability to cause large-scale devastation of the sea floor if not done properly, and that is partly due to the current proposed methods of how this will be accomplished, but also because the environment of the deep-sea is largely unstudied.
Deep-sea mining would primarily occur 4000-6000m deep in an area known as the Clarion-Clipperton Zone (CCZ). Most of the CCZ remains unstudied, and a vast majority of flora and fauna in that region and at that depth rely on the nodules for a source of hard substrate to bind onto. Once flora binds onto the substrate, communities are born.
Beyond the uses of them for organisms at that depth, many of these organisms are susceptible to changes in environment due to the niche conditions they live in. With this, large scale commercial operations could disturb the local environment by noise and light pollution, but also environmental consequences.
Additionally, the CCZ is a heterogeneous community, meaning surveys in one area does not correlate to the environment for the entire zone, meaning caution must be taken for each new area explored.
3.2: The Environmental Effects of Deep-Sea Mining:
Multiple components of the current methods arouse concern with many activists and ocean scientists alike due to the problems they could cause:
1. Locomotion System: Current methods mainly employ a traction based system, this has improved on previous renditions which proposed using an Archimedes’ screw, yet it proved too disturbing and inefficient for commercial deployment. And while a traction based system is an improvement, different studies have shown locomotion systems still pose a risk due to soil compaction, stress redistribution, and local habitat disturbance.
Figure 1. Archimedes’ screw can be used beyond moving a fluid, it can also be used to propel a vehicle forward under the same mechanism.
2. Collection System: A bucket system was the first idea companies researched, yet it proved to be too inefficient both environmentally and commercially, so it was abandoned for a suction collection system. While it is more efficient, early models have shown that it could disturb over 65,000 cubic meters of sediment per day of operation.
3. Dispersal After Collection: Nodules are pumped to the collection vessel using a riser system. But due to the way collection occurs, a slurry of sediment and nodules are pumped to the surface. The sediment is dispersed after the two are collected either in mid-water or near the bottom, both with their own consequences.
Sediment disturbance lies at the forefront of this conversation, due to both initial disturbance and dispersal later on. The abyssal plane, which is where deep-sea mining will occur, is found at depths between 3,000-6,000m and is characterized by vast, flat areas of the deep ocean floor that are generally located between the foot of a continental rise and a mid-ocean ridge. These underwater plains cover more than 50% of the Earth's surface, and many species in the abyssal plain rely on filter feeding as their source of acquiring nutrients, sediment disturbance could smother these organisms and other life [6].
Sediment dispersal back into the ocean runs the risk of altering the ocean chemistry in a vast swathe of sea if not mitigated, it also runs the risk of smothering life forms as well. Alterations of ocean chemistry though could be disastrous, as the sediment could be carried dozens of kilometers by currents in the water, causing areas outside of an initial mining zone to be affected as well [7].
Conclusion:
Ocean-based mining does host its fair share of potential problems, yet land-based mining primarily occurs in dense forests throughout the world that host some of the most biodiverse ecosystems anywhere on planet Earth, and yet mines have continuously devastated these environments for generations, and generations of people have been sent down into their depths not understanding the consequences on their health.
Communities have lived relying on the money these mines bring in, and the labor they provide, yet unaware of the diseases that fester in their bodies from the contamination surrounding them. This does not have to be the only way we attain the resources we need to power our modern world, the sea can provide.
While not everything is understood about the ocean, and the impacts mining could have. Entering this field with vigilance, caution, and with the spirit of innovation like so many before can create a new cleaner future.
About Noble Deep:
Noble Deep is a U.S.-based research and engineering company focused on minimizing sediment disturbance and plume generation in deep-sea resource extraction systems. Our mission is to make seabed mineral recovery scientifically guided, environmentally responsible, and publicly transparent. Learn more here.
References:
[1] B. Cox, et al., “The mining industry as a net beneficiary of a global tax on carbon emissions,” Communications Earth & Environment, 2022. [Online]. Available: https://www.nature.com/articles/s43247-022-00346-4
[2] U.S. Energy Information Administration, Energy and the Environment Explained. [Online]. Available: https://www.eia.gov/energyexplained/energy-and-the-environment/where-greenhouse-gases-come-from.php
[3] M. Lawson, The DRC Mining Industry: Labor and Formalization of Small-Scale Mining. [Online]. Available: https://www.wilsoncenter.org/blog-post/drc-mining-industry-child-labor-and-formalization-small-scale-mining
[4] Planet Tracker, Deep Sea Mining Could Be Worse for the Climate than Land Ores. [Online]. Available: https://planet-tracker.org/deep-sea-mining-could-be-worse-for-the-climate-than-land-ores/
[5] T. Stratmann, et al., “Polymetallic nodules are essential for food-web integrity of a prospective deep-seabed mining area in Pacific abyssal plains,” Scientific Reports, vol. 11, 2021. [Online]. Available: https://www.nature.com/articles/s41598-021-91703-4
[6] O. B. D. Jones, et al., “Long-term impact and biological recovery in a deep-sea mining track,” Nature, 2025. [Online]. Available: https://www.nature.com/articles/s41586-025-08921-3
[7] G. Petrossian, et al., “A precautionary tale: Exploring the risks of deep-sea mining,” Marine Policy, 2024. [Online]. Available: https://www.sciencedirect.com/science/article/abs/pii/S0308597X2400071X
[8] T. Norgate, et al., Assessing the Environmental Impact of Metal Production Processes. [Online]. Available: https://www.researchgate.net/publication/222402610_Assessing_the_environmental_Impact_of_metal_production_processes
