Acid rain 'could have benefits'

Wetland areas produce large quantities of methane

Acid rain pollution could be helping to slow down global warming, a study carried out in Scotland has found.

The rain, produced by industrial emissions of sulphur dioxide, has been shown to destroy forests and kill fish.

However, researchers from the Open University, who carried out a study on wetlands in Moray, think it may also have positive effects.

They believe it reduces the amount of the greenhouse gas, methane, produced by natural wetlands.

Methane generation

Methane is produced in large quantities by bacteria breaking down organic compounds in peat.

Like carbon dioxide, the gas contributes to global warming by forming a blanket that prevents heat from the Earth escaping into space.

As the climate gets warmer and wetter, more methane is generated by the microbes.

However, research by Dr Vincent Gauci, from the Open University's Department of Earth Sciences, showed that other bacteria which thrive on sulphur compete with the methane-makers.

We wouldn't want to give the impression that acid rain is a good thing Dr Vincent Gauci

Their numbers are so boosted by acid rain that they can significantly reduce methane generation from wetlands.

Dr Gauci, whose findings are published in the journal Proceedings of the National Academy of Sciences in the US, said: "Acid rain has such a big impact that it shuts down 30 to 40% of the methane in wetlands that are affected by this pollution.

"We wouldn't want to give the impression that acid rain is a good thing.

"But our findings suggest that small amounts of pollution may also have a positive effect in suppressing this important greenhouse gas.

"Moreover, they point to how complex the Earth system is."