activities, changing ecosystem structure due to fishing, to increases in atmospheric
CO
. The latter is changing the ability of reef organisms to create calcium
carbonate shells. Global warming is also causing widespread bleaching but
the fate of corals will not be determined by a single cause—effect relationship, but
rather by the interactive relationship between a number of human-driven
stresses. Similar analogies could be drawn throughout the world’s oceans.
Feedback processes also need to be considered. For example, during El Nin o
events coastal upwelling is severely reduced, and in consequence the release of
CO
from the equatorial Pacific to the atmosphere is constrained. If the
frequency of El Nin o events increases as a result of global warming this
mechanism may provide a negative feedback loop, reducing the release of
greenhouse gases to the atmosphere. However, a warmer ocean would have less
capacity to dissolve atmospheric CO
, providing a positive feedback loop. In
order to evaluate the magnitude of these feedback mechanisms we must identify
the principal pathways of energy and materials in key ecosystems, and evaluate
how these fluctuate as a result of global change.
Humans will be the ultimate receivers of changes in marine ecosystem
structure. An obvious direct concern would be the need to re-evaluate the use of
our marine resources should climate change and our own activities threaten the
supply of food. FAO projections for 2100 suggest that the amount of fish protein
per capita would at best be similar to 1998 levels, and at worse about a third
lower. Global change can reduce this even further. Improving our use of the 25%
of the total fish catch that is discarded annually as by-catch is a priority, as may be
the use of the landed catch. In this regard about 25% of the total fish landed is
used for animal feeds, often inefficiently. For example the proportion of fish meal
supplies used for farming fish has risen from 10% in 1988 to 33% in 1997, both
reflecting a trend towards farming carnivorous fish as well as the desire to
increase the growth of non-carnivorous species. Such trends bring into question
whether in the future fish farming will actually add to world fish supplies, the very
reason why aquaculture has been encouraged to develop over the last decades.
Fishing down pelagic resources to satisfy the expensive demands for top foods of
the developed world may be a faster way of generating further changes in marine
ecosystem structure than waiting for climate change to act.
The challenge of understanding a changing Earth demands the development of
a substantive science of integration. This science should be built on complex
systems analysis that addresses the synergies, interactions and non-linearities
that defy traditional cause—effect relationships. It must transcend disciplinary
boundaries across natural and possibly social science. The tools of the game are
available: paleo-environmental research, to understand processes that operate on
long time scales; Monitoring and observation systems, to make the most of the
expanding array of sophisticated remote sensors; Process studies, aimed at
resolving hot spots and bottom-up processes; and simulations, to describe and
P. W. Glynn, Tree, 1991, 6, 175—179.
R. L. Naylor, R. J. Goldburg, J. H. Primavera, N. Kautsky, M. C. M. Beveridge, J. Clay, C. Folke,
J. Lubchenco, H. Mooney and M. Tipell, Nature, 2000, 405, 1017—1024.
Influence of Climate Variability and Change on Marine Ecosystems
81
CO
. The latter is changing the ability of reef organisms to create calcium
carbonate shells. Global warming is also causing widespread bleaching but
the fate of corals will not be determined by a single cause—effect relationship, but
rather by the interactive relationship between a number of human-driven
stresses. Similar analogies could be drawn throughout the world’s oceans.
Feedback processes also need to be considered. For example, during El Nin o
events coastal upwelling is severely reduced, and in consequence the release of
CO
from the equatorial Pacific to the atmosphere is constrained. If the
frequency of El Nin o events increases as a result of global warming this
mechanism may provide a negative feedback loop, reducing the release of
greenhouse gases to the atmosphere. However, a warmer ocean would have less
capacity to dissolve atmospheric CO
, providing a positive feedback loop. In
order to evaluate the magnitude of these feedback mechanisms we must identify
the principal pathways of energy and materials in key ecosystems, and evaluate
how these fluctuate as a result of global change.
Humans will be the ultimate receivers of changes in marine ecosystem
structure. An obvious direct concern would be the need to re-evaluate the use of
our marine resources should climate change and our own activities threaten the
supply of food. FAO projections for 2100 suggest that the amount of fish protein
per capita would at best be similar to 1998 levels, and at worse about a third
lower. Global change can reduce this even further. Improving our use of the 25%
of the total fish catch that is discarded annually as by-catch is a priority, as may be
the use of the landed catch. In this regard about 25% of the total fish landed is
used for animal feeds, often inefficiently. For example the proportion of fish meal
supplies used for farming fish has risen from 10% in 1988 to 33% in 1997, both
reflecting a trend towards farming carnivorous fish as well as the desire to
increase the growth of non-carnivorous species. Such trends bring into question
whether in the future fish farming will actually add to world fish supplies, the very
reason why aquaculture has been encouraged to develop over the last decades.
Fishing down pelagic resources to satisfy the expensive demands for top foods of
the developed world may be a faster way of generating further changes in marine
ecosystem structure than waiting for climate change to act.
The challenge of understanding a changing Earth demands the development of
a substantive science of integration. This science should be built on complex
systems analysis that addresses the synergies, interactions and non-linearities
that defy traditional cause—effect relationships. It must transcend disciplinary
boundaries across natural and possibly social science. The tools of the game are
available: paleo-environmental research, to understand processes that operate on
long time scales; Monitoring and observation systems, to make the most of the
expanding array of sophisticated remote sensors; Process studies, aimed at
resolving hot spots and bottom-up processes; and simulations, to describe and
P. W. Glynn, Tree, 1991, 6, 175—179.
R. L. Naylor, R. J. Goldburg, J. H. Primavera, N. Kautsky, M. C. M. Beveridge, J. Clay, C. Folke,
J. Lubchenco, H. Mooney and M. Tipell, Nature, 2000, 405, 1017—1024.
Influence of Climate Variability and Change on Marine Ecosystems
81