Who would have thought that smog had an upside? It may be the scourge of China鈥檚 urban citizens and a prickly PR problem during the Olympics, but surprisingly, the pea-soupy fallout from Chinese industrial pollution could be reducing the country鈥檚 contribution to climate change from at least one greenhouse gas.
A British team has been adding sulphate to laboratory rice paddies in an effort to mimic the effect of acid rain on Asia鈥檚 most important food crop. This equivalent of typical acid rain reduced methane emissions from flooded paddies by up to 25 per cent, says Vincent Gauci of the Open University in Milton Keynes in the UK (Journal of Geophysical Research, ).
Methane from agriculture is the second most important human-made greenhouse gas after carbon dioxide, and by some estimates up to a third of it comes from methane-generating bacteria lurking in rice paddies. So Asia鈥檚 thickening smogs could be good news, in one respect, for the global climate. That鈥檚 as long as the acid rain does not simultaneously reduce the yield of rice fields, causing farmers to flood more and more fields to maintain production.
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In fact, says Gauci, 鈥渢he acid rain seems to increase rice yields鈥�. That may be how the unexpected methane suppression operates. By boosting grain production, the sulphur helps plants retain organic matter that once disappeared from their roots to trigger the manufacture of methane in the flooded fields.
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