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Acid rain OK?
AN OPEN UNIVERSITY research team has recently claimed that
acid rain could reduce the output of one of the greenhouse gases – methane –
that gives rise to global warming. Acid rain is caused by emissions of sulphur
dioxide, typically released by burning coal in power stations. The sulphates in
acid rain destroy forests and kill fish and other aquatic species.
Dr Vincent Gaudi and his colleagues from the Open University
studied the effects of introducing sulphates, at the concentrations found in
acid rain, into wetland environments, such as marshes and peat bogs, in Britain,
Sweden and the USA. The results showed that methane emissions were reduced by
between 30-40%, which is important because methane is one of the gases in the
environment that causes global warming. The report of the research in the
Proceedings of the National Academy of Sciences in the US asserts that, as a
result of acid rain, outputs of methane could be reduced in time to
pre-industrial levels.
Methane producing microbes, known for short as MAs, are
present in all global wetlands and contribute to global warming. However, there
is another group of microbes present in wetlands known for short as SRBs, whose
activity is increased by higher levels of sulphates in the environment.
According to the theory put forward, when SRBs are stimulated by high sulphate
concentrations they take food from the MAs, which as a result are less active,
leading to a fall in their methane output.
There are countervailing tendencies at work also, because
global warming itself tends to increase MA activity and therefore methane
output. But using computer models designed by NASA, the US Space Agency, the
authors conclude that the net effect will still be to reduce the greenhouse
effect.
This research shows the complex nature of the eco-system and
the need to consider it and its interactions as a whole. Does it, though, show a
way forward to tackle the problem of global warming? To answer this question it
is first necessary to get confirmation that the results presented are generally
applicable. The authors of the article, for example, only considered a limited
geographical area. There needs to be further research to test that there were no
special factors at work in the countries they studied which could limit the
global relevance of their findings.
Even if the theory is confirmed, the question of scale need
to be considered. Although methane as a result of microbe activity may be
reduced by 30-40%, emissions not due to this microbe account for the majority of
world methane output. Because of this, the researchers are claiming that methane
from all sources will be reduced only by 15% in 2030. But this chemical,
although a powerful greenhouse gas, only accounts for 22% of the greenhouse
effect, because there is much less of it produced than the main global warming
culprit, carbon dioxide. The net effect would therefore be an amelioration of
just 3.3% in the greenhouse effect.
Although estimates vary about the required reduction of the
greenhouse effect to achieve environmental sustainability, they start at 50% and
many environmental activists think that the cuts need to be much higher. When
seen in this perspective, the claim of Dr Gaudi (quoted by the BBC) that acid
rain is offsetting climate warming quite dramatically is not borne out.
For a very small reduction of one environmental threat, that
only scratches the surface of the problem of global warming, there would be a
continuation of the damage caused by acid rain, one which capitalist
governments, after coming under enormous pressure, have very belatedly started
to tackle. Blair’s government, which is increasingly falling behind its
commitments to reduce UK greenhouse emissions, may be tempted to present this as
a justifiable trade-off, but it is actually no answer at all to the
environmental threats looming over us.
Pete Dickenson
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