Where is peat found?
In the British landscape before widespread enclosures and ‘improvements’, peatlands occurred almost everywhere. By early 1900, this had changed dramatically leaving a tattered rump of this once expansive resource. The most extensive British peatlands are now found in upland areas of moorland and blanket mire, from Dartmoor, Exmoor, and Bodmin in the south-west, to the Pennines along
FIGURE 1.2 Types of bog in Ireland reproduced with permission from John Cross 1989.
England’s spine, and then the hills and lower mountains of Scotland. Along the western seaboard, especially of the Scottish Highlands, in Ireland itself, and the islands around both these, are extensive blanket mires and raised bogs. Tracing the great river valleys, and in particular in their lower floodplains such as the Solway Firth and the Flanders Moss complex around the River Forth in central Scotland, are also the remains of once much greater peat bogs. In lowland and more southerly areas such as the Cambridgeshire Fens, the Cheshire and Shropshire Meres, and the Somerset Levels, there are relatively extensive peat bogs and fens. On drier heaths and moors are shallow peats and organic soils. Detailed historical research has shown former peat bogs and fens in areas that today would be almost unthinkable (Figure 1.2).
Peat or turf?
Confusingly there is no satisfactory definition of these two terms concerning the fuels and materials to which they refer. The site of peat extraction can be a turbary, a turf pit, a peat moor, a fuel allotment, or very often a peat moss. In many areas, the place-name of the local settlement or manor is attached to the local peat moss and this is the turbary for that area. For example, in Lancashire there are Leighton and Leighton Moss, and Silverdale and Silverdale Moss. The material itself is sometimes separated into ‘peat’ for the deeper stuff, and ‘turf’ for the shallower tops, but this is not always so. Sometimes ‘turf’ is also used for the deeper peats. There are also localised and technical names with often subtle meanings in terms of brown fibrous peat from the higher levels and deeper, hard black peats from lower down. Turf is always the name used for thin heather and grass sward cut from drier sites and burnt, and the same implement, a turfing spade, was used for horticultural grass turf as well. These thin turves were generally considered poor fuel, but they did burn hot with high silica content from sandy soils, and in some areas were quite prized. Overall though, the vocabulary can be quite confusing.
The peat-forming plants
Most familiar peatlands such as in northern temperate regions have been developed by the long-term accumulation of sphagnum mosses, but other species (e.g. cotton-grasses, purple moor-grass) may also be important. Also, in fen vegetation in lowland regions the peat is from Phragmites, Carex, and associated vegetation. In southern temperate regions such as New Zealand or Tasmania for example, peat may be from sphagnum or mostly from other bog-forming species in waterlogged sites. In the Falklands, for example, peat may be from sphagnum mosses or a mix of grass and ericaceous species and simply develops where the wet, cool conditions slow the rates of organic decomposition.
There is a diversity of peat-forming species in the tropics for example, and in the southern hemisphere (as noted above). Tropical peat-formers vary from mangrove species in coastal zones to big trees in the swamp forests. These different peat-formers are introduced and described in the relevant chapters and their contributions to ecosystem services are considered.
Carbon storage
Contemporary peatlands contain around 500 gigatons of carbon which is about twice of that held in the global forests. Another often overlooked importance of peatlands is concerning water, with around 10% of the world’s freshwater in peat sites. Furthermore, damage to peatlands has been responsible for increases in both flooding and drought. Unlike carbon storage in trees, woods, and forests for example, that in peat remains trapped in the soil system and safely locked away from the atmosphere. Generally, trees and other woody vegetation die and then decompose and the carbon is released again as carbon dioxide, though in peat forests, remains of the trees largely go on to form peat and the carbon moves into long-term storage. With peatlands, the carbon is held securely unless the site is drained and the peat breaks down. Indeed, one of the key problems for temperate peatlands in the twenty-first century is the history of drainage and associated over-intensive land use. Soil moisture content is a key part of the delicate balance of the peat bog.
