Geoscience Reference
In-Depth Information
atmospheric CO
2
, would reduce the CO
2
entering
the ocean, but costs are thought to be high. Another
option is CO
2
capture and storage (CCS), the extrac-
tion of CO
2
from the point of production (such as a
power plant) and its long-term disposal in either
the deep oceans or in suitable geological repositor-
ies thus removing it from contact with the atmos-
phere (IPCC 2005). Adding quicklime to the oceans
may well remove CO
2
from the atmosphere and
sequester it in the world's oceans (see
www.
Cquestrate.com,
accessed July 2010), and may
make the oceans more alkaline and directly combat
ocean acidii cation. Nonetheless, the potential side-
effects are unknown and the scale of the project
enormous, with estimates of around 1.6 billion m
3
of limestone required to sequester each gigatonne
(Gt) of carbon. Currently the ocean is absorbing
about 2 Gt of anthropogenic carbon per year.
Another issue with geoengineering is that grow-
ing publicity may imply to society and policymak-
ers that it provides ways to avoid the consequences
of climate change, and that actions to reduce CO
2
emissions can be delayed. There may also be strong
public opposition to attempts to engineer the planet
on a scale substantially larger than that seen for a
small-scale research project off Hawaii into ocean
injection of CO
2
(E. Adams, pers. comm.), which
was called off due to mounting public concern.
Efforts to mitigate the effects of ocean acidii cation
could take two other forms: adaptation or remedia-
tion. Adaptation accepts that lower ocean pH will
occur and have socio-economic impacts and so
adjusts economic activity and resource management
to take this into account. For instance, if marine con-
ditions become unfavourable for commercially val-
uable i sh species in their present habitat, i sh
farmers may choose to switch to controlled produc-
tion environments in onshore tanks or ponds, or to
take measures to control pH at a local scale in the
marine environment around the i sh farm.
Remediation, on the other hand, seeks to restore
ocean pH to a level that would avoid negative
effects. That is, it may be possible to inl uence
local and regional ocean pH through geoengi-
neering schemes over limited periods of time; but
this has not been demonstrated and could carry
with it costly ecological side-effects. For this rea-
son research is necessary to provide scientii c evi-
dence to enable policymakers to select those
solutions with the least risk of unintended envi-
ronmental consequences that are the most ethical,
economic (from the monetary and carbon per-
spective), and effective at doing the job. In this
case, developing codes of practice and govern-
ance for future possible application of geoengi-
neering techniques is an important focus for
future policymaking. Independent international
interdisciplinary teams are required to assess new
geoengineering techniques as they emerge.
Clearly the most obvious and optimum policy
option for mitigating ocean acidii cation is to reduce
fossil fuel CO
2
emissions to the atmosphere through
the UNFCCC climate change negotiations currently
under way (see Chapter 14 ).
13.9 Conclusions
Ocean acidii cation is a recently recognized phe-
nomenon, with the same cause as climate change—
increased anthropogenic CO
2
emissions. Experi-
ments, modelling, and an increasing number of
in
situ
measurements point to the likelihood of sig-
nii cant and developing changes to ocean chemis-
try with the potential to affect natural marine
systems, including chemical cycling and ecosys-
tems. Such chemical changes have been shown to
affect a wide range of marine organisms, espe-
cially, but not exclusively, those which utilize
CaCO
3
to build protective and supporting struc-
tures, such as shells and reefs. The nature of the
chemistry of CO
2
in seawater is such that some
ocean areas, notably polar regions, are likely to be
affected i rst. Coincidentally these high-risk areas
are the sites of the greatest production of marine-
based human food resources. With an increasing
world population becoming more reliant upon
marine resources for human consumption, and
with existing pressures such as pollution, i sheries
exploitation, and coastal development, any further
stress to these resources through ocean acidii ca-
tion is of concern. If the future impact on marine
systems is as some studies suggest, the ramii ca-
tions for policymaking are wide ranging.
Communication regarding ocean acidii cation,
the threats it may present, what these threats mean
to the human population, and the timescale through
