MadSci Network: Earth Sciences

Re: Correlation between rain forest destruction and loss of glacial ice

Date: Mon Dec 14 12:20:16 2009
Posted By: Will Higgs, Consultant
Area of science: Earth Sciences
ID: 1260292243.Es

There are quite a few questions in your message, but unfortuantely the jury
is still out on climate change and although plenty of cut-and-dried answers
are on offer the increasing politicisation of the problem means that any
simple treatment of this complex question should be treated with
circumspection.  It seems clear that there is a warming trend, and a
significant increase in CO2 in the atmosphere, but the cause or causes are
far from obvious, as are the solutions.

Glaciers, like rivers, are dynamic structures depending upon a balance
between input and output.  The recession of glaciers could be due to
reduced snowfall, but is just as likely to be due to increased melting in
the lower reaches.  In fact, global warming should result in increasing
amounts of water vapour in the air, and thus precipitation, as higher
temperatures mean more evaporation from the ocean surface.

The point that no-one seems to get past the biodiversity issue is an
interesting one. I believe that climate change is now seen as an issue
behind which different varieties of campaigners can unite, and while an
individual may be campaigning on a simple climate change ticket, they may
actually be more concerned about other types of pollution or biodiversity
loss, and see the restriction of mindless industrial development as a good
thing for all sorts of reasons.

Whether destruction of forests contributes to the increase in CO2 is
debateable because the carbon in living organisms is part of the natural
carbon cycle - the carbon circulating in the atmosphere and biosphere,
which is normally in balance.  It is carbon from the burning of fossil
fuels which comprises the extra amount, forest destruction being a bad
thing for many other reasons.  Of course, destruction of trees does release
CO2 into the atmosphere, but a similar amount should be re-absorbed by the
plants which grow to replace those lost trees.  For the same reason,
deliberate re-afforeststion is unlikely to reduce the amounts of CO2 in the
atmosphere significantly as those new trees must die eventually, but
planting forests may be a good thing for other reasons.  

Yes, all plants absorb CO2 when photosynthesising, and give off oxygen. 
The carbon from the CO2 is used by the plant as the basis for manufacturing
the various compounds such as proteins, fats and carbohydrates from which
all living things are made.  More CO2 is absorbed by plankton in the
surface waters of the oceans than by terrestrial plants, however, and it is
more likely to be permanently sequestered on the bottom of deep oceans when
these organisms die and sink.

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