What of the Future? - Climate Change Impacts on Freshwater Ecosystems - page 286

carbon dioxide to the atmosphere from respiration of carbon stores in soils and
sediments, thus reinforcing the warming trend. It is not impossible that the
converse, major negative feedbacks, may eventually occur in what is a colossal
and complex earth chemical system to annihilate the roots of change in a grand
manifestation of Le Chatelier's principle. And if the rates of processes, on which
experimentation is possible to help the predictions, have a considerable uncertainty,
the collective future behaviour of human societies, each with different cultures,
historical conditioning, wealth and aspirations, is virtually unforeseeable, except in
the very general terms of archaeological patterns.
Is it therefore of any value at all to scan the future? Not to do so is to abandon
future generations to fate, to rest in a self-satisfaction and irresponsibility that
might make things much worse. There are lessons of history that natural climate
change, in concert with intrinsic factors, has often destroyed whole cultures and
civilizations. Archaeologists might argue that civilizations repeatedly rose again,
that we are merely in part of a usual cycle, but ecologists will point out that what
was then local was reparable elsewhere, but that there is no 'elsewhere' for what
is global. It would be a betrayal not to try to foresee consequences when even
very imperfect predictions give some chance of avoidance.
Consequently we have attempted a foresight of how freshwater systems, and
particularly their consequences for human societies, might change given 2 °C and
4 °C temperature increases within the 21st century. We contemplated the effects
of an even greater increase now that 4 °C seems very likely whilst at least 2 °C
seems inevitable. The potential devastation that would be created by a greater
than 4 °C rise (widespread melting of the polar glaciers, rises in sea level of the
order of metres, release of enormous quantities of methane from the northern
peatlands and tundras), however, makes any prediction too uncertain. Complete
chaos is, by its very nature, completely unpredictable. We decided to hold the
optimistic view that human societies will do what is necessary to halt the rise at
4 °C and the over-optimistic view that temperatures might be held down to 2 °C.
The chances of the latter, failing extensive popular insurrection and complete
collapse of current economies, seem low at present. We also bore in mind that
climate change will not be the only major problem confronting human societies
in the next several decades. Population increase and the increasing depletion of
crude oil are two further horsemen of the Apocalypse.
Our approach was to use discussions among experts from within Euro-
limpacs to create scenarios for the present, and for these two temperature
markers likely to be reached in the mid and late 21st century (and possibly
rather earlier), respectively, in five broad geographical areas: Arctic-Boreal,
e.g. northern Sweden or Finland; mid-latitude continental e.g. Poland, France,
Germany; maritime peninsulas and islands, e.g. Iceland, the United Kingdom,
Ireland, Denmark; Mediterranean lands, e.g. S. France, Iberia, Italy, Greece;
and finally the high mountains of the Alps, Pyrenees and Carpathians. To
standardize this thought experiment, we envisaged for all but the mountains a
model catchment in each zone that is about 10 4 km 2 and about half-covered
with natural or semi-natural vegetation and half with appropriate agriculture/
pasturage. It had some villages and a small town with 100,000 people and a
maximum elevation of 1,000 m falling to a flat plain. What follows is, of course,