Conservation and Sustainable Use of the Biosphere - WBGU

230 F The biosphere in the Earth System
and the South Pacific (Behrenfeld and Kolber, 1999).
For that reason Martin (1990) suggested fertilizing
these regions with iron in order to increase the
amount of CO 2
absorbed by the oceans. It is, however,
unclear whether the food chain would respond
as expected, what amounts would be necessary and
how ultimately the linked atmosphere-ocean system
would respond. Initial experimental results show an
effect on the marine ecosystem (increase in productivity
and chlorophyll concentration) but not on CO 2
concentration (Denman et al, 1996). Model results
show that the atmospheric CO 2
concentration after
100 years of iron fertilization could be reduced by at
most 10 per cent of the concentration anticipated for
2100. The IPCC (1996a) does not therefore see iron
fertilization as a suitable climate protection measure.
Currently, however extensive in-situ experiments are
being carried out (Coale et al, 1998; Section F 5).
F 3.3.2
Scenarios for the future
Coupled atmosphere-ocean models that are used to
project climate change so far contain only very simple
representations of marine biogeochemical and
biogeophysical processes. The carbon cycle models
used for the IPCC stabilization scenarios work on the
assumption that the ocean’s currents and the biological
pump remain unchanged (IPCC, 1996a).
Sarmiento et al (1998) calculate using a coupled
atmosphere-ocean circulation model that the current
carbon sink in the Southern Ocean can change dramatically
in just a few decades: increased precipitation
can lead to greater stratification so that less carbon
is transported to the depths and less warmth is
released from the ocean into the atmosphere. Both of
these can result in the ocean absorbing less CO 2
.This
investigation shows that an improved model of
marine processes is required in order to be able to
evaluate the changes in the biological pump
(Schimel, 1998).Arrigo et al (1999) show that the biological
pump is weakened when there is increased
stratification in the Ross Sea (in the Southern
Ocean) because the composition of phytoplankton
species is changed. This could also mean a reduction
in the CO 2
absorption of the ocean, a positive feedback
that has not been considered in any of the scenarios
up to this point. In light of the critical influence
of phytoplankton on the future CO 2
absorptive
capacity of the ocean, about which too little is known,
additional investigations with regard to the interaction
between the carbon cycle, climate change and
the marine biosphere remain essential.
F 3.4
Research requirements
In the IPCC stabilization scenarios (IPCC, 1996a)
assumptions with regard to terrestrial and marine
biosphere and the ocean currents were made that,
although still very much up to date and having gained
relevance in both policy and practical terms in the
context of the Framework Convention on Climate
Change, have since been supplemented. Above all,
the complexity and diversity of feedbacks between
atmosphere, organisms, soils and inorganic substances
has been specified to a greater degree in such
a way that the uncertainties with regard to the carbon
cycle at global level are better evaluated and a new
basis for calculation of scenarios has been created.
The development of better models has been crucial
to developing an understanding of the ecological
processes on a global scale and thus to making sufficiently
reliable prognoses of the response of ecosystems
to climatic changes and increased carbon dioxide
levels. Currently, in almost all individual questions
with regard to biospheric C absorption there is
a need for more research, but it is widely accepted
that older forests, moors and wetlands merit particular
protection from a global point of view.
For the Kyoto follow-up conferences and the calculation
of biological sinks, it will be fundamental to
define more precisely the absorption capacity of individual
terrestrial ecosystem types as is envisaged currently
in several research projects. It is also essential
to clarify the behaviour of vegetation communities
and of soils in specific geographic zones in the case of
future warming. Whether the organisms in the sea
will play a greater role in the future as C reservoirs
and in which regions they could be influenced by fertilization
will remain the task of further Earth System
analyses. Before work can really begin in this regard
on effective Earth System management, more precise
scientific results should be awaited and above all
evaluated in connection with socio-economic and
politico–institutional findings. Be that as it may, it
continues to be essential on the emissions side that
countries meet their greenhouse gas reduction commitments
as agreed in Kyoto – essential both for
them and for the global environment.