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that such systems, honed by the utterly ruthless mechanisms of natural selection
to be as near fit for purpose as possible, are just as crucial to us, indeed much
more fundamentally so, than the local grocer, filling station or hospital. The
chemistry of the biosphere is the ultimate sine qua non of our existence. Damaged
ecosystems, including all agricultural ones, do not store as much carbon as intact
ones. James Lovelock's contribution was to point this out.
We have responded rather oddly to the increasing damage we have caused by
attempting to value in classical economic terms the goods and services we draw
from ecosystems, to demonstrate their importance (Costanza et al . 1997; Balmford
et al . 2002). This has been influential in drawing attention to their very great
apparent value and in helping communicate with economists and politicians. But
perhaps we have completely missed the point. They are not items that can be used,
misused, repaired, ignored or traded at will. They are outside the current economic
system. What they do in maintaining the equable state of the planet for all living
organisms, including us, is so fundamental as to be priceless. It would be
inconceivable, as William Shakespeare (1623) well knew 400 years ago, through
the wonderful speech of Portia in The Merchant of Venice , to value the blood as a
separate component of the body. What is sine qua non supersedes evaluation. Yet
we damage the biosphere as casually as we throw away our rubbish, and in
contemplating the hitherto effects of climate change, we fail to realize that the loss
of ecosystems and the changing climate are mutually linked. Indeed, we blithely
cost the damage of climate change (Stern 2006) as we cost the goods and services
we are losing through application of the same approach of classical economics. We
have failed to see the interaction of climate, ecology and equability. Our attempts
to mitigate climate change, in a desperate bid to avoid disruption of our societies,
may inevitably be doomed to failure unless we begin to see the whole picture and
not just the components we find most convenient to our cash economy.
Water and the freshwater biota
Though the ultimate driver of climate change effects will be temperature, the
immediate executive will be the availability of freshwater. Freshwater systems
stitch together the biosphere through the hydrological cycle. The stitching,
however, can become undone, and the surface freshwater component is perhaps
the most vulnerable part of the hydrosphere. Living organisms absolutely need
liquid water. The ability of liquid water to persist is a fundamental characteristic
of a planet capable of supporting life based on carbon compounds. The creation
of conditions allowing its existence is the ultimate triumph of the biosphere. The
Earth in chemical equilibrium would be so hot as to bear only water vapour.
Moreover, human history is, at bottom, an account of the availability of water for
drinking, crop growing and sanitation. It follows from the effects of climate
change through floods and droughts that the next century, even the next few
decades, will likely see more disruption of human activities than has been
experienced in the evolution of our species.
For the freshwater systems and organisms with which this topic is concerned,
the detailed effects of moderate climate change could vary from being disastrous
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