28 November 2010

How peat bogs could save mankind

Posted by vivienne

Sphagnum moss in the foreground and then miles of peat bog on the Merrivale firing range near Cut Hill, Dartmoor (caption thanks to photographer)

Peat bogs may be partly-rotted piles of plants, but they could squelch into action against climate change. Scientists from Bangor University are investigating whether bogs can be coaxed into locking carbon dioxide out the atmosphere for thousands of years.

Peat bogs already soak vast amounts of carbon dioxide from the air – they cover about two to three percent of the Earth’s surface and store about 455 billion tonnes of carbon in peat. To put that in perspective, humans release 29 billion tonnes of carbon dioxide each year. Peatland plants are great at sucking carbon dioxide out of the atmosphere when they photosynthesise. The trouble is much of that carbon is lost when the plants rot, before it can get locked up in peat.

Professor Chris Freeman and his colleagues think they can make peat bogs keep a firmer grip on their carbon by slowing the already-sluggish rate plants rot in peat bogs with dams, genetically-modified sphagnum moss or paper mill waste. Should this work, Professor Freeman says it would turn the bogs into giant sponges to suck up our carbon dioxide emissions and ‘bag’ them away

Engineering peat bogs is better in theory than other ideas for vacuuming up carbon dioxide like growing and burying lots of trees, Professor Freeman says. Peat bogs, unlike forests, don’t compete with other land uses like crop growing or housing. Possibly the only modern use of peat is potting compost. Altering peak bogs would be cheap, effective and – if the planet overcooled – he says we could burn or dry the peat to release carbon dioxide

Professor Freeman’s brainwave to save the planet is relatively recent. A laboratory designed to test his ideas – the Wolfson Carbon Capture Laboratory – was opened in May 2010. But his theory for how bogs break down plant material and the effect this could have on climate change was published in Nature in 2001

His Nature paper solved a long-standing puzzle: why are peat bogs different from drylands? People have always been fascinated by why decomposition is incredibly slow in peat bogs. Plants and, in rare cases, human bodies can remain preserved for thousands of years. Bog bodies like Lindow Man, Britain’s most famous bog body, often have their internal organs intact despite dying between 2BC and 119AD.

People used to think peat bogs were the land that rot forgot because they lacked oxygen. Microbes were less active in waterlogged oxygen-deprived soil and struggled to break down plants and dead Iron Age dudes. When Professor Freeman looked into this, he had problems finding any evidence for the idea that decomposing microbes were less active in oxygen-limited environments. Microbes are also active in sewage treatment works and cows’ stomachs, despite the lack of oxygen

Professor Freeman studied the enzymes peatland microbes use to break down plant material. He found one enzyme, phenol oxidase, become much more active in drier peat. This enzyme breaks down phenolics – chemicals produced by sphagnum moss that, according to Professor Freeman, also give tea its brown colour. Phenolics are the chemicals that slow down rot in peat bogs by dampening down microbe activity. They starve the microbes by preventing them producing the enzymes they need to turn plant material into nutrients. Dead bodies and plants are slow to break down in wet peat because it’s full of phenolics. Should the peat dry out, phenol oxidase breaks down the phenolics and allows the microbes to become active. Professor Freeman called this mechanism the ‘enzymic latch’.

Slowing down peat bog decomposition involves strengthening the enzymic latch by, for example, genetically-engineering moss to produce more phenolics. Alternatively, scientists could increase the waterlogging of the peat to deactivate phenol oxidase using dams. Regardless of what they choose, this is a quirky and interesting idea and I will follow the project with interest. I heard Professor Freeman’s talk at Geoengineering – taking control of our planet’s climate at the Royal Society in London earlier this month