Geoscience Reference
In-Depth Information
(see previous section) could favor CO
2
storage in the ocean. This
would be a negative feedback to the increase in the atmospheric
concentration in CO
2
[GEH 11]. There are few current global models
taking this process into account, partly because the large variability of
responses make its parametrization difficult [GEH 07]. Despite this
limitation, all models converge toward a small associated reduction in
pCO
2
in response to decreased calcification. Beyond the direct effect
of a decline of calcification on CO
2
fluxes, reduced rates of
calcification could significantly affect the export of organic matter to
the deep ocean [GEH 11]. Indeed, calcium carbonate acts as a ballast
that facilitates carbon export through sedimentation. A decreased
production of calcium carbonate could, therefore, decrease
the exportation of organic carbon toward deep waters, reduce the
efficiency of the biological pump, and therefore act as positive
feedback to the increase in atmospheric CO
2
. Barker
et al.
[BAR 03]
were the first to consider this mechanism. Their study of sensitivity
shows that this positive feedback is of the same scale as the negative
feedback associated with the drop in calcification.
5.4.3.
Economy and society
The evaluation of the economic and societal impacts of ocean
acidification is complex and often hampered by the difficulty in
extrapolating scant and sometimes inconsistent scientific data. It has
already been mentioned that there are only a small number of studies
on species of commercial interest. The experiments have often been
carried out in laboratories, in conditions which do not represent the
natural environment well, and over short durations, leading to results
sometimes contradictory or different depending on the species
considered. Works on the potential for adaptation or acclimation are
almost non-existent, as well as for the response of communities and
ecosystems. Occasionally, the processes measured are of limited
interest for economists, for example, the reduction in calcification is
not particularly useable as is. An effect on the edible part of the
organism would be more interesting in an economic and societal
context [HIL 13]. Generally, it is difficult to associate a cost with a
service offered by an ecosystem, since it often involves indirect
