Blue carbon sink
Salt marshes
Fact box 5. Geo-engineering proposals
for mitigating CO
2
Mangroves
Interest has been growing in the use of geo-engi-
neering to provide a technically and potentially
commercially viable mitigating solution to combat
Seagrasses
increasing atmospheric CO
2
concentrations (see
IPCC, 2005 for an overview). Several of these pro-
posals intend to enhance the function of the ocean
0.2
as a carbon sink, or to store CO
0.4
2
in subsea geologi-
cal formations. Some of these suggestions might
0.3
sound dramatic and farfetched, but if the concepts
1.8 are scientifically sound and technically feasible, they
Shelf
should not be disregarded. However, evaluating
Estuaries
these new innovations is in most cases not a simple
story, as they pose significant ecological, econom-
26.6
ic, political and ethical challenges (Nature News,
Deep Sea
2009) giving cause for concern. With too many un-
known variables and current modeling limitations,
assessment of the risks and consequences of these
proposals will be a challenge.
There are two main approaches. The first is to re-
duce energy entering the earth’s system by block-
ing radiation so it cannot be absorbed in the first
instance (e.g. spraying aerosols to increase cloud
cover, use of solar shades, increasing reflective ca-
Organic carbon burial rate
pacity of urban areas); the second is to reduce the
Teragrams per year
concentration of CO
2
in the atmosphere by trans-
Maximum
ferring it into long term storage reservoirs, thereby
facilitating the escape of energy from the earth
Marine habitat area 330
Million square
Minimum (Lenton and Vaughn, 2009; IEA, 2004). These ap-
kilometres Average
proaches are at varying degrees of development;
while some have been through in-situ experimen-
17.5
tation, others are still just theoretical. Current re-
search shows that most ocean geo-engineering
concepts are high risk for undesirable side-effects
6.5
(e.g. increase in ocean acidification), have limited
application, uncertain outcome and potentially
non-reversible impacts on the marine environment.
1.80
This highlights the need to apply a precautionary
Source: Cebrián and Duarte,
approach when investigating ocean geo-engineer-
1996; Duarte et al., 2005a; 0.0002 ing interventions.
and Bouillon et al., 2008.
Figure 17: Blue carbon sinks.
39
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