Expert reaction to the Manchester moorland fires

Sue Page, Professor of Physical Geography from our School of Geography, Geology and the Environment, has provided expert comment on the Saddleworth Moor fire which has been raging for three days.

Professor Page said: “The fires are taking place in an area of upland Britain that has extensive peatlands.

“Peatlands are a globally important carbon pool. While covering only ~3% of the Earth’s land surface, they contain an estimated 500 to 700 billion tonnes (Gt) of carbon, which is between 32 and 46% of the total soil carbon pool (~1500 Gt) and likely exceeding that contained in the world’s vegetation (500 Gt). By any comparison, peat-forming ecosystems are a significant component of the global carbon cycle.  Peatlands cover 11% of England’s land area and are most extensive in the uplands, including the Peak District. They contain around 584 million tonnes of carbon.

“In peatland ecosystems, fires comprise both flaming and smouldering combustion. While flaming, surface fires consume vegetation and litter, smouldering fires burn into and below the ground consuming the peat itself as a fuel source. Flaming fires may pass rapidly through the vegetation but smouldering fires burn slowly and persist for long periods of time, burning repeatedly in response to changing soil moisture and penetrating to different peat depths.  They can also smoulder and then reignite (as we see in the Saddleworth moor fire). Smouldering combustion is a low-temperature process that proceeds under reduced oxygen availability.  Peat moisture is the main factor limiting peat ignition and the start of the smouldering combustion process and fires will not usually establish in peat with a high moisture content. The recent hot, dry spell of weather will have dried out the peat surface, but moisture content may also have been lowered by previous land drainage (e.g. to improve grazing for livestock).

“The incomplete combustion that occurs during smouldering peat fires means that they are responsible for more substantial atmospheric and air quality impacts than vegetation fires. In addition to emissions of greenhouse gases (carbon dioxide and methane), they are the source of toxic gases (e.g. carbon monoxide, benzene, hydrogen cyanide) and also high levels of small particulates (PM2.5 - particulate matter with diameter less than 2.5 micrometres). Recent research on peat fire events in SE Asia has demonstrated that this dense, toxic smoke poses significant health risks to human communities both within immediate proximity of the fires and at greater distances since smoke plumes can be transported over tens or even hundreds of kilometres from the source of the fires.

"This is a pertinent issue for this densely-populated regions where there is the potential for exposure of large numbers of people to smoke inhalation. This may result in an increased incidence of respiratory and cardiovascular conditions, particularly amongst children, the elderly and those with pre-existing respiratory problems. In addition, peat smoke contains many carcinogenic gases such as hydrogen cyanide, ammonia and benzene that could result in a longer-term increase in ill health and mortality in the smoke-affected population.

“For the Saddleworth Moor fire, a further concern is the industrial legacy of this region, with the peat soils containing the 'fall-out' from many years of heavy industry in surrounding towns and cities.  The peat soils contain this pollution legacy in the form of increased levels of heavy metals, which will also be liberated into the smoke by the fires.  Although I am not aware of any UK-based research on this issue, research in Canada has shown volatilisation of harmful levels of mercury during peat fires.”