Swedish scientists have found that flatulent shellfish are creating vast amounts of greenhouse gases, leading to a predictable slew of comments about farting cockles and clams. But beneath the schoolboy humour, there is a serious point. The two gases in question – methane and nitrous oxide – are potent agents of climate change, with a warming potential 28 and 265 times greater than carbon dioxide respectively.

Scientists studying the Baltic Sea off the coast of Sweden have found that shellfish are producing one-tenth of all the greenhouses gases released there – the equivalent to the amount produced by 20,000 cattle. If the same situation is being replicated around the rest of the world’s seas and oceans, we have a serious problem.

Chief scientist Stafano Bonaglia, from Stockholm University, is certainly concerned: “It sounds funny, but small animals in the seafloor may act like cows in a stable, both groups being important contributors of methane due to the bacteria in their gut.”

He also points out that shellfish were releasing these gases long before global warming became an issue, and believes that the recent emissions may have been exacerbated by the enrichment of coastal waters, due to the run-off from agricultural fertilisers.

To put this into perspective, the average cow produces 120kg of methane every year – 1,000 times as much as even the most flatulent human. With almost 100m head of cattle in the US alone, that means that 12m tonnes of gas are being released annually, dwarfing the efforts of the shellfish.

The major animal producers of methane are cud-chewing creatures known as ruminants, such as cattle and sheep – it’s the bacteria in their stomachs that causes the problem. However, kangaroos have a different digestive system, so produce a lot less methane – kangaroo steak, anyone?

Other creatures that create huge amounts of methane include the world’s 2,000-plus species of termite. Each only produces a tiny amount – roughly half a microgram a day, so it would take 2m termites to produce a daily dose of one gram of methane. However, there are so many of them that their annual emissions may top 20m tonnes a year. The big difference between termites and cattle is, of course, that termites – and the gases they release – are part of the natural ecosystem. Cattle aren’t.