The Effect on Our Oceans

Deep seabed mining could cause irreversible harm to our oceans, from the seafloor to the surface and the midwater columns in between

Industrial scale deep seabed mineral mining (DSM) has never successfully occurred anywhere in the world. This is due, in part, because the deep oceans are poorly understood. The immense pressure, at depths of 200 meters and more, makes it difficult to access and expensive to explore and monitor. And despite being the largest ecosystem on the planet, humanity knows more about the surface of the moon than we do about our deep sea ecosystems. (Sharma, 2017; Drazen et al., 2020) However, for over a decade scientist have been warning the international community of the alarming shifts the ocean’s water column is experiencing, and is expected to experience, as a result of climate change. (Davies et al., 2007; Dunn et al., 2018; Johnson et al., 2018) The midwater column is important to the stability of global marine biodiversity and the ocean food webs. (Danovaro et al., 2004) And although many of the direct impacts remain unknown, it is inaccurate and dangerous to claim that DSM will not directly affect the stability of the midwater column through the discharge of sediment plumes and noise.

The deep-sea water column (>200m) makes up roughly 93% of habitable ecosystem for the entire planet, land and sea, and plays a vital role in sustaining marine biodiversity. (Danovaro et al., 2008) It has only been in the last decade that we have begun studying the shallowest part of this immense ecosystem: the mesopelagic water column (200-1000m), also known as the twilight zone. Current modelling predicts that the twilight zone’s fish populations are the most abundant of any species on the planet and number 100x more than the current global annual fish catch. (Irigoien et al., 2014) The importance of this water column on global biodiversity cannot be understated. It is therefore vital that we recognize and seek to fully understand the unavoidable impacts DSM will have on this region and the consequences of those impacts on the rest of the ocean systems, specifically the Cook Island fisheries. To ensure effective protection of the marine environments and avoid causing serious and irreversible harm, the Cook Islands must ensure a precautionary approach to any mineral activity, including exploratory mining activities.

The precautionary approach has been established as a valuable tool for environmental protection within international law. Considered the founding codification of the principle, article 15 of the 1992 Rio Declaration on Environment and Development states:

In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

It is possible that permittable exploratory mining activities, even cautiously applied, cause irreversible harm due to a lack of scientific certainty.(Levin et al., 2016) In fact, it is generally accepted that DSM activities will inevitably cause irreversible loss of marine biodiversity with still unknown domino impacts on the rest of the ocean system.(Niner et al., 2018) It is therefore important that the CI Seabed Minerals Authority fully understand the “threats of serious or irreversible damage” that exist prior to issuing mining licenses and approving applications. To fully comprehend the risks of rushing this process and the importance of supporting the international calls for a 10-year deep-sea mining moratorium, we need look no further than the recent failure of Papua New Guinea’s NZD$160m deep-sea mining venture.

The collapse of PNG’s Solwara-1 mining site is evidence that the technology required to effectively protect the marine environment and ensure a precaution-based approach to mining activities is not available and should be a warning to all Pacific Island nations. It is crucial that we take precaution-based steps to understanding the impacts of DSM, not only on the deep seabed but throughout the midwater column, our shallow water shorelines and our beaches.


Danovaro, R., Dell’Anno, A., and Pusceddu, A. (2004). Biodiversity response to climate change in a warm deep sea. Ecol. Lett. 7, 821–828.Danovaro, R. et al. (2008) ‘Exponential Decline of Deep-Sea Ecosystem Functioning Linked to Benthic Biodiversity Loss’, Current Biology, 18(1), pp. 1–8. doi: 10.1016/j.cub.2007.11.056.
Davies, A. J., Roberts, J. M. and Hall-Spencer, J. (2007) ‘Preserving deep-sea natural heritage: Emerging issues in offshore conservation and management’, Biological Conservation, 138(3–4), pp. 299–312. doi: 10.1016/j.biocon.2007.05.011.
Drazen, J. C. et al. (2020) ‘Midwater ecosystems must be considered when evaluating environmental risks of deep-sea mining’, Proceedings of the National Academy of Sciences of the United States of America, 117(30), pp. 17455–17460. doi: 10.1073/pnas.2011914117.
Dunn, D. C. et al. (2018) ‘O C E A N O G R A P H Y A strategy for the conservation of biodiversity on mid-ocean ridges from deep-sea mining’, (July), pp. 1–16. Available at:
Irigoien, X. et al. (2014) ‘Large mesopelagic fishes biomass and trophic efficiency in the open ocean’, Nature communications, 5(May 2013), p. 3271. doi: 10.1038/ncomms4271.
Johnson, D., Adelaide Ferreira, M. and Kenchington, E. (2018) ‘Climate change is likely to severely limit the effectiveness of deep-sea ABMTs in the North Atlantic’, Marine Policy. Elsevier Ltd, 87(October 2017), pp. 111–122. doi: 10.1016/j.marpol.2017.09.034.
Levin, L. A. et al. (2016) ‘Defining “serious harm” to the marine environment in the context of deep-seabed mining’, Marine Policy. Elsevier, 74(October), pp. 245–259. doi: 10.1016/j.marpol.2016.09.032.
Niner, H. J. et al. (2018) ‘Deep-Sea Mining With No Net Loss of Biodiversity—An Impossible Aim’, Frontiers in Marine Science, 5(March). doi: 10.3389/fmars.2018.00053.
Sharma, R. (2017) Deep-Sea Mining: Resource Potential, Technical and Environmental Considerations. Edited by R. Sharma. Springer. doi: 10.1007/978-3-319-52557-0.

The predicted impacts of deep seabed mineral mining on the marine environments of the deep ocean midwater columns and the effected ecosystem services. Graphic Credit: (Drazen et al., 2020)