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Climate change threatens blanket bogs

Wed, 09/12/2012 - 5:24am
Natural Environment Research Council

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Climate change threatens blanket bogs

12 September 2012, by Tom Marshall

Climate change could shrink the regions suitable for blanket bogs, a rare and ecologically valuable habitat, according to a recent study.

Blanket bog on the Isle of Skye

Found in damp coastal regions at high latitudes, the bogs are home to a unique range of wildlife. Yet the rising temperatures expected over the coming century will mean many existing blanket bogs face conditions beyond those in which they can remain healthy and carry on growing. These habitats need to remain wet, and struggle to cope with average temperatures above 15°C.

Blanket bogs are areas in which layers of peat cover the whole landscape, not just its lowest and most waterlogged areas. As elsewhere, this peat builds up from layer upon layer of dead moss and other plant matter; the waterlogged, oxygen-poor conditions slow down the process of decomposition. But if the bog dries out, peat deposits that took millennia to accumulate can break down much more quickly.

Scientists were already concerned about how these delicate ecosystems would cope with climate change, but this is the first time these risks have been explored in a rigorous way. The researchers built a model that simulates the area suitable for blanket bogs under a range of different climate scenarios.

Angela Gallego-Sala in the Outer Hebrides

Angela Gallego-Sala in the Outer Hebrides.

They found that if climate change continues as expected, many blanket bogs will be left outside their climatic limits within the next few decades. They won't disappear overnight, but they'll almost certainly stop growing and will be increasingly vulnerable to erosion. On top of their ecological importance, the bogs hold vast quantities of carbon, and if they were to dry out they would be more likely to start to lose this carbon to the atmosphere, triggering further climate change.

'No-one has managed to map out the likely impact of climate change on blanket bogs until now,' says lead author Dr Angela Gallego-Sala of the University of Exeter. 'Our study has revealed how vulnerable they are. It is now crucial for a plan to be put in place to protect these unique ecosystems and the wildlife they support.' Protecting wetlands from climate change is a difficult task, but we do know of some possible approaches - for example, researchers have had some success blocking drainage channels that were cut into upland areas over the twentieth century so that water drains off them more slowly.

It's a particularly pressing concern in the UK, where blanket bogs cover some 700,000 hectares in places stretching from Devon to Shetland - an estimated 10 to 15 per cent of the world's total stock of this habitat. The model suggests that if we don't control emissions, climate change could cut this by around 84 per cent, ultimately leaving only a tiny remnant in a few parts of western Scotland.

'Blanket bogs are part of the rich tapestry of the British countryside and provide vital life support services for people and wildlife,' says Dr Harriet Orr of the Environment Agency, which co-funded the study, adding that it strengthens the case for cutting greenhouse gas emissions in an effort to limit the effects of climate change.

It's possible that elsewhere, in parts of Norway, Russia, Canada and Alaska rainfall will increase, creating new areas where blanket bogs can form. But this isn't certain and would in any case take decades or even centuries to happen. The researchers drew on seven different climate models, and only a minority project that these new bog-friendly zones will arise.

The study's authors come from the Universities of Bristol and Exeter in the UK and from Australia's Macquarie University. They say it's important we develop a plan to protect blanket bogs. As well as giving a home to rare plants and animals and helping regulate the climate by locking up carbon from the atmosphere, they also absorb and filter rain water, providing clean drinking water and controlling flooding in downstream areas. They also preserve valuable archaeology.

Gallego-Sala says that loss of peat bogs is a serious environmental problem all over the world; she's just returned from Indonesia, where extensive tropical peatlands are being drained, potentially emitting vast stocks of carbon into the atmosphere over a short period.

The results appear in Nature Climate Change. Its authors also contributed to a more detailed paper focusing only on British peat bogs, published in Climate Research. Both studies were funded by the Environment Agency and the Natural Environment Research Council.

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