Offsetting the change

Climate change resulting from greenhouse gases in countries like China and India is being offset by acid rain, according to researchers from Manchester Metropolitan University's (MMU) Earth Systems Science group.

Curiously, the smog plaguing Asian cities appears to be mitigating one of the worst greenhouse emissions - methane - which is 21 times more powerful as a greenhouse gas than CO₂, and is a by-product of the Asian paddy field.

The British team of MMU's Prof Nancy Dise and Dr Vincent Gauci of the Open University added sulphate to laboratory paddies in an effort to mimic the effect of acid rain on Asia’s most common food crop. The acid rain surrogate reduced methane emissions by up to a quarter.

The reduction in pollution happens during a stage of the life cycle when the rice plant is producing grain. This period is normally associated with around half of all methane emissions from rice and the team found that simulated acid rain pollution reduced this emission by 24 per cent.

The researchers produced similar results when they exposed natural wetlands to simulated acid rain, but believe that their new findings could be more important since natural wetlands are mostly located far from major pollution sources, whereas for rice agriculture, the methane source and the largest source of acid rain coincide in more urban environments.

One line of investigation the team would like to confirm is that the sulphate component of acid rain may actually boost rice yields. This might, paradoxically, have the effect of reducing a source of food for the methane-producing microorganisms that live in the soil.