Ecology. Danger of deep-sea mining

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www.sciencemag.org SCIENCE VOL 316 18 MAY 2007
987
CREDIT: RALPH WHITE/CORBIS
POLICYFORUM
O
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
2
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.
References
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, resourceinvestor.com.
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
(2005).
7. H. Thiel, Forschungsverbund, Tiefsee-Umweltschutz, in
ISOPE: Ocean Mining Symposium Proceedings, Tsukuba
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the Expert Workshop held at the International Academy
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10. M. D. Hannington et al., “A global database of seafloor
hydrothermal systems” (Geological Survey of Canada,
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11. J. Schneider, Neues Jahr. Geol. Palaeontol. Abh. 208,
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12. J. Halfar, R. M. Fujita, Mar. Policy 26, 103 (2002).
10.1126/science.1138289
Plans for deep-sea mining could pose a serious
threat to marine ecosystems.
Danger of Deep-Sea Mining
Jochen Halfar
1
and Rodney M. Fujita
2
ECOLOGY
1
Department of Chemical and Physical Sciences,
University of Toronto at Mississauga, Mississauga,
Ontario, Canada, L5L 1C6; e-mail: jochen.halfar@
utoronto.ca.
2
Environmental Defense, Oakland, CA
94618, USA; e-mail: rfujita@environmentaldefense.org
Published by AAAS