THE Arctic is belching out nitrous oxide – commonly known as laughing gas. Unfortunately, the punchline is that it is a powerful greenhouse gas.
Previously, emissions of N2O into the atmosphere were thought to come mainly from tropical forests and intensively managed farmland, with a negligible amount from northerly environments.
Maija Repo and colleagues from the University of Kuopio, Finland, measured emissions from peat circles in northern Russia. These sit on peatland plateaux, which are widespread in the Arctic, covering 20 per cent of the total land surface. The bare surfaces of peat circles develop because cycles of freezing and thawing churn up the peat, preventing plant growth.
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They found the peat circles emitted 1.2 grams of N2O per square metre per snow-free season – as much as tropical forests emit annually. The team reckons that a lack of plants lessens competition for nitrogen minerals. This allows nitrates to accumulate in the soil which are then metabolised by bacteria to produce N2O (Nature Geoscience, ).
Although this means N2O remains a minor contributor to the greenhouse effect – compared with methane and carbon dioxide – it persists unaltered in the air for over 110 years, compared with about 10 years for methane.
Unfortunately, global warming may promote peat-churning and expand bare areas. Since the flow of the gas from the peat circles is so rapid, even a small increase in bare surfaces would cause significant increases in emissions of N2O, says Repo.