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Ecology. Danger of deep-sea mining

Authors: SCIENCE VOL 316 18 MAY 2007
ver the past few months,
the possibility of mineral
exploitation in the deep
sea (1) has moved closer to reality
with completion of the first
undersea exploration for massive
sulfide deposits. Analyses of tar-
get deposits in a zone of active
hydrothermal vent systems in the
territorial waters of Papua New
Guinea (PNG) have revealed gold,
copper, zinc, and silver in concen-
trations that far surpass those of
current terrestrial mining ven-
tures (2). With mining technology
in an advanced stage of develop-
ment, skyrocketing metal prices,
and depletion of metal-rich terres-
trial mines, sea-floor mining act-
ivities are now scheduled to begin by 2009.
Initial interest in deep-sea mining was
centered on extracting manganese nodules
from spatially extensive sea-floor deposits in
international seas distant from continents.
However, ratification of the United Nations
Convention on the Law of the Sea in 1994,
which imposed financial burdens and environ-
mental safeguards, together with low metal
prices, drastically lowered interest in nodule
mining. Prospecting and exploration activities
have since shifted to the Exclusive Economic
Zones (EEZs), where it is the responsibility of
individual nations to issue mining licenses and
define environmental safeguards. Discovery
of extensive massive sulfide deposits at com-
mercial ore grades within the EEZs of PNG
and, more recently, New Zealand has set off a
new phase of exploration (3).
The first site for such mining is expected to
be the Manus backarc basin of PNG, in close
proximity to active sulfide-forming hydrother-
mal vent systems. Hydrothermal vents are
home to unique and diverse ecosystems (4).
They are not only of scientific interest, but are
being explored for pharmaceutical and biotech-
nological applications (56). Whereas individ-
ual manganese nodule mine claims extend
across sea floor areas the size of Switzerland,
massive sulfide mining will concentrate on
small (1 km
in size),
high-grade deposits with-
in the uppermost 20 m of
the sea floor. An average
of 2 megatons of ore per
year is to be extracted by
Nautilus Minerals, Inc.,
in a single strip-mining
operation using remotely
operated underwater mine
cutters. It will be trans-
ferred from the sea floor
to a mining platform by
hydraulic pumps (6).
Environmental risks
including benthic distur-
bances, sediment plumes,
and toxic effects on the
water column have been
assessed for the large manganese nodule min-
ing endeavors in the equatorial Pacific (7).
These risks were judged to be so large and
unpredictable that a number of studies recom-
mended the abandonment of manganese min-
ing efforts to avoid a large-scale and long-term
risk to Pacific ecosystems and fisheries (8).
Benthic disturbances and far-reaching sedi-
ment plumes would probably be less during
massive sulfide mining (relative to nodule
mining) because of the absence of sediment
cover on the recently created ocean floor of
active hydrothermal vent systems. However,
explored mining sites are less than 1 km from
active vents, where there is a likely potential of
smothering, clogging, and contamination of
vent communities by drifting particles.
Organisms surviving these perturbations
would be subject to a radical change in habitat
conditions with hard substrata being replaced
by soft particles settling from the mining
plume (5). Mining could also potentially alter
hydrologic patterns that supply vent commu-
nities with essential nutrients and hot water. A
further problem may arise during dewatering
of ores on mining platforms, resulting in dis-
charge of highly nutrient enriched deep-water
into oligotrophic surface waters, which can
drift to nearby shelf areas.
These impacts may not be limited to eco-
systems within the EEZ of the country issuing
mining permits and could thus be in violation
of international environmental law (9). If the
first deep-sea mining effort is successful, a
wave of interest in deep-sea mining of mas-
sive sulfide deposits is likely to result. In fact,
250 of these deposits have been identified in
deep-sea areas worldwide (10).
There has been little progress toward cre-
ation of environmental regulatory systems
specific to deep-sea mining by governments
with jurisdiction over massive sulfide depos-
its. Some of these governments have a poor
track record of mine oversight and regulation
on land, so prospects appear poor for sound
regulation of underwater mining (11, 12). It is
time to implement scientific, technological,
and legal measures to minimize negative en-
vironmental impacts (including discouraging
deep-sea mining activities near sensitive
habitats) and to set up mechanisms to recover
costs of regulation and enforcement from this
nascent industry. Large capital investments
and generation of revenues by underwater
mining operations are likely to make regula-
tion after onset of commercial operations
even more difficult once deep-sea mining
becomes a reality.
1. J. L. Mero, The Mineral Resources of the Sea (Elsevier,
Amsterdam, 1965).
2. K. Heilman, “Nautilus one step closer to undersea min-
ing,” 4 October 2006,
3. G. P. Glasby, Science 289, 551 (2000).
4. C. L. Van Dover et al., Science 294, 818 (2001).
5. P. A. Rona, Science 299, 673 (2003).
6. D. Clifford, Mining Magazine 2005 (September), p. 58
7. H. Thiel, Forschungsverbund, Tiefsee-Umweltschutz, in
ISOPE: Ocean Mining Symposium Proceedings, Tsukuba
Japan, 21 to 22 November 1995 [International Society of
Offshore and Polar Engineers (ISOPE), Golden, CO,
1995], pp. 39–45.
8. Tusch Research Group, in Proceedings International
Symposium Kiel Institute of International Law, R.
Wolfrum, Ed., Kiel, Germany, 17 to 20 May 1989
(Duncker & Humblot, Berlin, 1990).
9. L. Glowka, in Managing Risks to Biodiversity and the
Environment on the High Sea, Including Tools Such as
Marine Protected Areas: Scientific Requirements and
Legal Aspects, H. Thiel, A. Koslow, Eds. (Proceedings of
the Expert Workshop held at the International Academy
for Nature Conservation, Isle of Vilm, Germany, 27
February to 4 March 2001 [BfN (Bundesamt für
Naturschutz) Skripten 43, Federal Agency for Nature
Conservation, Bonn, Germany, 2001), pp. 195–204;
10. M. D. Hannington et al., “A global database of seafloor
hydrothermal systems” (Geological Survey of Canada,
Open File 4598, 1CD-ROM, Ottawa, 2004).
11. J. Schneider, Neues Jahr. Geol. Palaeontol. Abh. 208,
397 (1998).
12. J. Halfar, R. M. Fujita, Mar. Policy 26, 103 (2002).
Plans for deep-sea mining could pose a serious
threat to marine ecosystems.
Danger of Deep-Sea Mining
Jochen Halfar
and Rodney M. Fujita
Department of Chemical and Physical Sciences,
University of Toronto at Mississauga, Mississauga,
Ontario, Canada, L5L 1C6; e-mail: jochen.halfar@
Environmental Defense, Oakland, CA
94618, USA; e-mail:
Published by AAAS
... After International Court of Justice (2014) source for cobalt, manganese, copper, and nickel (Childs 2020). Recent projections over the past decade and a half have reiterated the imminence of DSM (Halfar and Fujita 2007;Allsopp et al. 2013;Heffernan 2019), with Nauru's triggering of the 'two-year rule' possibly commencing the overcoming of the largest regulatory barrier to date (Thaler 2021). The possibility of commercial DSM activity has evolved through the form of a distant possibility to a near inevitability (Carrington 2017). ...
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The growing importance of cobalt to the US economy has led to its categorisation as a critical mineral. Cobalt demand is increasing due to its requirement in lithium-ion batteries, which will significantly contribute to the energy transition. Supply is threatened for various reasons, primarily regarding supply chain concentrations, with the majority of the world’s cobalt originating in terrestrial deposits in the Democratic Republic of the Congo, and being refined in China. There remain environmental and ethical concerns over the present supply chain. Previous discussions around reducing cobalt’s criticality have suggested diversifying processing locations to reduce geographical and jurisdictional reliance where possible. This study assesses the viability of extracting cobalt from polymetallic nodules (PMNs) located on the deep-seabed in the Area, as an alternative strategy to reduce cobalt’s criticality. Assessments are made of the viability of PMN extraction considering ongoing barriers to introduction, contrasted with current arguments supporting PMN extraction. PMN mining offers a more stable and decentralised alternative to current cobalt supply. There exist impediments to its introduction, notably potential environmental impacts, which remain poorly understood. Technical and political restrictions must also be overcome. It is argued that the wider environmental benefits of increased cobalt supply from PMN mining may offset its detrimental environmental impacts. It is suggested that PMN mining be used in a wider strategy to improve supply security of cobalt to US markets.
... D espite increasing interest in deep-sea mining, there are long-standing concerns about environmental impacts on vulnerable and poorly understood ecosystems (1)(2)(3). These concerns took on new urgency in June 2021, when the Republic of Nauru notified the International Seabed Authority [ISA, the intergovernmental body erected by the UN Convention on the Law of the Sea (UNCLOS) responsible for managing seabed resources in areas beyond national jurisdiction] of intent to sponsor an exploitation application for polymetallic nodule mining in the Pacific in 2 years. ...
... The seabed ore-collection process disturbs the shallow sediments of the seabed, and the resuspended sediments change the chemical properties of the water body, which eventually has an impact on the survival of organisms [100]; this is the most direct impact brought about by the mining of deep-sea polymetallic nodules. ...
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With the increase in demand for metal resources, research on deep-sea polymetallic nodule mining has been reinvigorated, but the problem of its environmental impact cannot be ignored. No matter what method is used for mining, it will disturb the surface sediments of the seabed, thereby increasing the concentration of suspended solid particles and metal ions in the water body, changing the properties of the near-bottom water body and sediments, and affecting biological activity and the living environment. Focusing on the ecological and environmental impacts of deep-sea polymetallic nodule mining, taking as our main subject of focus the dynamic changes in sediments, we investigated the environmental impacts of nodule mining and their relationships with each other. On this basis, certain understandings are summarized relating to the ecological and environmental impacts of deep-sea polymetallic nodule mining, based on changes in the engineering geological properties of sediment, and solutions for current research problems are proposed.
... Once plastic particles reach the sediments, they may remain buried there for millennia ). However, natural processes (i.e., bottom currents, turbidity currents, and deep-sea circulation) and anthropogenic activities (i.e., bottom trawling, dredging, drilling, and deep-sea mining) may disturb marine sediments and rerelease plastic back into oceanic circulation (Wilber and Clarke 2001;Halfar and Fujita 2007;Puig et al. 2012;Kane et al. 2020;Pohl et al. 2020;Sala et al. 2021). Reducing plastic inputs is imperative to avoid marine plastic pollution from becoming a chronic problem, but reducing disturbance to marine sediments is also fundamental to avoid a legacy problem, where buried plastics is being resuspended. ...
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About 15 Tg of plastic are estimated to enter the ocean yearly, with this figure growing exponentially every year. Assessments of floating marine plastic amount to 0.2% of the expected plastic stock, implying that 99.8% is stored in a sink yet to be identified. Marine sediments are believed to be the ultimate sink for oceanic plastic, however, there is currently no global estimate of the plastic load stored there. Here, we synthesize available estimates of micro‐ and mesoplastic stocks in marine sediments and, by integrating stocks across different habitats, we conservatively estimate a load of 170 Tg (25–900 Tg) of nonfibrous plastic globally accumulated in marine sediments from 1950 to 2010, most of which at intermediate depths (200–2000 m). This estimate, despite the uncertainty, is two to three orders of magnitude higher than the floating plastic stock and confirms marine sediments as a major plastic sink.
... Although terrestrial mining will likely dominate supplies of critical metals in the medium term, the International Seabed Authority, an organisation under the UN Convention on the Law of the Sea, is currently drafting regulations relating to seabed mining 51 . While the prospects of oceanic mining of minerals could alleviate the supply constraints worldwide 51 , the process needs to be science-based to ensure environmental safeguards, which should be put in place to mitigate the risk of accidental damage to the fragile ecosystem in the deep-seas 52,53 . ...
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Battery-electric vehicles (BEV) have emerged as a favoured technology solution to mitigate transport greenhouse gas (GHG) emissions in many non-Annex 1 countries, including India. GHG mitigation potentials of electric 4-wheelers in India depend critically on when and where they are charged: 40% reduction in the north-eastern states and more than 15% increase in the eastern/western regions today, with higher overall GHGs emitted when charged overnight and in the summer. Self-charging gasoline-electric hybrids can lead to 33% GHG reductions, though they haven’t been fully considered a mitigation option in India. Electric 2-wheelers can already enable a 20% reduction in GHG emissions given their small battery size and superior efficiency. India’s electrification plan demands up to 125GWh of annual battery capacities by 2030, nearly 10% of projected worldwide productions. India requires a phased electrification with a near-term focus on 2-wheelers and a clear trajectory to phase-out coal-power for an organised mobility transition. India’s plans to electrify transport is complicated by its reliance on coal-power. Here the authors call for diverse policy and technology solutions, including a focus on cleaner grids, electric 2-wheelers, and hybrid 4-wheelers in the near-term.
... Deep waters fisheries, including bottom-trawling, operate globally and have relevant impacts on the deep waters ecosystems that have long recovery times (Clark et al. 2016). Deep-sea mining is an emerging industrial activity that is thought to radically affect the whole deep-water ecosystem (Halfar & Fujita 2007;Van Dover et al. 2017;Niner et al. 2018), which would include effects on top predators such as deep-diving cetaceans that rely on deep waters resources to survive. ...
China has committed to peaking its CO2 emissions by 2030 in order to achieve its 2060 carbon neutrality target. Heavy-duty trucks (HDTs) are an important area to decarbonize, given the continuously rising greenhouse gas (GHG) emissions in this sector. Various low-carbon options have emerged, yet a comprehensive understanding of the extent to which these options can decarbonize HDT throughout the life cycle remains limited. Here, we adopt a life-cycle analysis to assess and compare the GHG mitigation potential ofhighly efficient diesel engines, battery-electrics, and hydrogen fuel cells for China’s class-8 HDTs in 2030. Results show that all three options could enable >38% life-cycle GHG reductions. The battery-electric option, however, requires well-established fast-charging infrastructures to maintain the freight-carrying capacity that will otherwise be compromised by larger batteries. Hydrogen fuel cells can attain 80% reduction when paired with low-carbon hydrogen. Hybrid strategies, including improving engine efficiency, decarbonizing power grids, optimizing freight logistics, and incentivizing behavioral changes, are necessary for the efficient and effective HDT decarbonization that is key to China achieving carbon neutrality by 2060.
Industrial seabed mining is expected to cause significant impacts on marine ecosystems, including physical disturbance and the generation of plumes of toxin-laden water. Portmán Bay (NW Mediterranean Sea), where an estimated amount of 60 Mt of mine tailings from sulphide ores were dumped from 1957 to 1990, is one of the most metal-polluted marine areas in Europe and worldwide. This bay can be used to assess the impact on marine ecosystems of particle settling from sediment plumes resulting from mine tailings resuspension. With this purpose in mind, we conducted a field experiment there to investigate subsequent effects of deposition of (artificially resuspended) contaminated sediments on (i) prokaryotic abundance and meiofaunal assemblages (in terms of abundance and diversity), (ii) the availability of trophic resources (in terms of organic matter biochemical composition), and (iii) a set of ecosystem functions including meiofaunal biomass, heterotrophic C production and C degradation rates. The results of this study show that mine tailings resuspension and plume deposition led to the decline of prokaryotic abundance and nematode's biodiversity. The later decreased because of species removal and transfer along with particle resuspension and plume deposition. Such changes were also associated to a decrease of the proteins content in the sediment organic matter, faster C degradation rates and higher prokaryotic C production. Overall, this study highlights that mine tailing resuspension and ensuing particle deposition can have deleterious effects on both prokaryotes and nematode diversity, alter biogeochemical cycles and accelerate C degradation rates. These results should be considered for the assessment of the potential effects of seabed mineral exploitation on marine ecosystems at large.
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Within the endemic invertebrate faunas of hydrothermal vents, five biogeographic provinces are recognized. Invertebrates at two Indian Ocean vent fields (Kairei and Edmond) belong to a sixth province, despite ecological settings and invertebrate-bacterial symbioses similar to those of both western Pacific and Atlantic vents. Most organisms found at these Indian Ocean vent fields have evolutionary affinities with western Pacific vent faunas, but a shrimp that ecologically dominates Indian Ocean vents closely resembles its Mid-Atlantic counterpart. These findings contribute to a global assessment of the biogeography of chemosynthetic faunas and indicate that the Indian Ocean vent community follows asymmetric assembly rules biased toward Pacific evolutionary alliances.
Many serious potential direct or indirect environmental impacts are to be expected from marine mining of nearshore-, shelf- as well as from deep searesources. Today the more or less harmful hazards cannot be quantified in every detail, but the general dangers for the various marine environments are foreseeable by all means. This is true for coastal and shelf regions offshore of countries which have several of the resources described below as well as for the manganese nodule mining in the international zone of the deep sea. Drastic future conflicts between industrialised and other nations concerning the marine resources, the common heritage of mankind, cannot be excluded. The sea is not only a source for the satisfaction of our present resource needs. Already today the seas are sinks for a large number of harmful pollutants stemming from our civilisation. A plundering of the sea for further economical growth can be disastrous for the various marine environments and means that future generations will be deprivated of the benefits of the sea.
Interest in deep-sea mining developed in the early 1970s, with a focus on manganese nodules in international waters. Mining may actually occur first, however, on rich polymetallic sulfide deposits associated with hydrothermal vents within exclusive economic zones. Even though mining for polymetallic sulfides may not take place for several years, precautionary performance standards, environmental regulations, and the establishment of Marine Protected Areas may help guide the marine mining industry toward a goal of minimizing environmental impacts. Once substantial investments in prospecting and exploring a potential mining site are made, implementation of environmental regulations may prove to be much more difficult.
In his Perspective, [Rona][1] reviews recent advances in knowledge of sea-floor resources. Knowledge is expanding from those minerals eroded from land--metals, gemstones, sand, and gravel--to those minerals concentrated by plate tectonic processes in ocean basins. Exploration of the oceans is at an early stage and development of marine mining is subject to economic and environmental considerations. [1]:
The first attempt to exploit deep-sea manganese nodules ended in failure as a result of the collapse of world metal prices, the onerous provisions imposed by the U. N. Conference on the Law of the Sea (UNCLOS), and the overoptimistic assumptions about the viability of nodule mining. Attention then focused on cobalt-rich manganese crusts from seamounts. Since the mid-1980s, a number of new players have committed themselves to long-term programs to establish the viability of mining deep-sea manganese nodules. These programs require heavy subsidy by host governments. Gold-rich submarine hydrothermal deposits located at convergent plate margins are now emerging as a more promising prospect for mining than deep-sea manganese deposits.
  • J Schneider
  • Neues Jahr
J. Schneider, Neues Jahr. Geol. Palaeontol. Abh. 208, 397 (1998).
  • C L Van Dover
C. L. Van Dover et al., Science 294, 818 (2001).
Including Tools Such as Marine Protected Areas: Scientific Requirements and Legal Aspects
  • L Glowka
L. Glowka, in Managing Risks to Biodiversity and the Environment on the High Sea, Including Tools Such as Marine Protected Areas: Scientific Requirements and Legal Aspects, H. Thiel, A. Koslow, Eds. (Proceedings of the Expert Workshop held at the International Academy for Nature Conservation, Isle of Vilm, Germany, 27 February to 4 March 2001 [BfN (Bundesamt für Naturschutz) Skripten 43, Federal Agency for Nature Conservation, Bonn, Germany, 2001), pp. 195–204; _cache=1&L=1.
  • H Thiel
  • Forschungsverbund
  • Tiefsee-Umweltschutz
H. Thiel, Forschungsverbund, Tiefsee-Umweltschutz, in ISOPE: Ocean Mining Symposium Proceedings, Tsukuba Japan, 21 to 22 November 1995 [International Society of Offshore and Polar Engineers (ISOPE), Golden, CO, 1995], pp. 39–45.