Introduction to Peatlands

Cotton grass on Thorne Moors, south Yorkshire. Photo: Peter Roworth

Peatlands are a particular type of wetland environment, typically characterised by ombrotrophic (nutrient poor) conditions and dominated by plants and insects that thrive in these conditions. 

Sphagnum mosses and ericaceous shrubs tend to dominate, while shrub vegetation such as birch and willow may be found around the drier edges of the peat system. Insects which can tolerate acidic conditions include a wide variety of beetles, which may live in acidic bog pools or feed on bog plants and mosses. A lagg fen may exist around the edges of a mire as it is influenced by ground water. These areas are minerotrophic (more nutrient-rich) and less acidic, this results in a wider variety of flora and fauna, such as mixed deciduous woodland.  The growth of peat means that these landscapes become divorced from regional hydrological processes, instead becoming dependent on atmospheric moisture in the form of precipitation for their nutrients. 

There are three broad peatland habitats in the UK and Ireland:

  • Fens: peatland environments that receive their water from precipitation and groundwater. There are a wide variety of fen environments. 
  • Blanket bogs: peatlands which receive all their water from precipitation. They are globally rare, but are the largest UK peatland habitat.
  • Raised bog: peatlands which form in low lying areas, typically floodplains or basins or close to the sea. Raised mires are rain fed (ombrotrophic) and are therefore composed of nutrients, pollutants and minerals that are derived directly from the atmosphere, with limited influence from groundwater. They often start as fens, becoming independent of the underlying water table and become increasingly more acidic (ombrotrophic). They can be identified by their peat domes. 

In the UK, peatlands are diverse ecosystems and have depths ranging from 0.3m to more than 11m. They form in uplands and lowlands, coastal and inland areas, and can often be found under forestry or cultivation. Many suffer from degradation and drainage. Our varied peatlands have distinct traits, land-use histories, and restoration potential.

Peats start to accumulate in situations where conditions are waterlogged, typically through two main pathways of development: terrestrialisation and paludification, which both require water-logged conditions to be present. Terrestrialisation involves the in-filling of a water body (e.g. lake) by living and dead plant material, which gradually build up to fill the basin and eventually progress to raised mire via a marsh and fen stage. This is the most common way raised mires are formed in the UK, Ireland and Europe. Some well-known examples include Sluggan Bog in Northern Ireland, Bolton Fell Moss in England and Temple Hill Moss in Scotland.  Paludification is well known in coastal North America, parts of the UK and Ireland, Scandinavia and Germany. At these locations previously dry land surfaces became water-logged (often due to rising water tables caused by localised flooding or sea level rise) and quickly in-filled, with peat growing both upwards and outwards. 

Lowland raised bog mire expanse.
Stribers Moss, Roudsea Wood and Mosses NNR, Cumbria.
Credit: © Natural England/Jacqueline Ogden, licensed with CC BY-NC-ND 2.0.

Because of the way peat develops, it traps carbon from the plants and animals that were growing on the peatland, trapping carbon into the peat. This means peat is usually a carbon sink, absorbing carbon. However, when peat is burnt or dried, it releases this trapped carbon from thousands of years ago back into the atmosphere, contributing to greenhouse gases, making peat in this condition a carbon source. More carbon in the atmosphere causes an increase in global temperatures, encouraging a drier, warmer climate and further decomposition of peatlands. We explore these ideas within the section Peatlands and Climate.

The layers of moss and other vegetation that make up peat are themselves immensely valuable as past environment and climate archives. The pioneering palaeoecologist, Sir Harry Godwin (1981), first popularised the concept of peat as an ‘archive’ of information about the past. Within their deposits are preserved the remains of their past biodiversity and by detailed studies of these remains, it is possible to document their formation, from inception to their present form, yielding climate and cultural histories that demonstrate the intensely interconnected human-environment relationships at the heart of the climate crisis. 

Peatlands also contain remarkable archaeological artefacts, their waterlogged and anaerobic nature preserving organic materials that are usually lost. These include items such as trackways, bog bodies, votive objects as well as every-day items lost as people travelled across the wetlands. In some cases, it clear that people living within the wetlands, adapting to living in these places and developing distinctive ways of life.

Neolithic trackway, Hatfield Moors, South Yorkshire. Photo: Henry Chapman.

Historically, peatlands have been important too for the collection of wild resources, fuel and as refuges, serving as an important support for communities and traditional practices across extensive areas of Britain, Ireland and the Atlantic region. These landscapes and communities are well represented within 18th-21st century art, photography, poetry and literature (our title takes inspiration from Seamus Heaney’s description of human-peat relationships, in his poem ‘Digging’), often through images of disappearing but iconic landscapes, that hark back to a simpler or romanticised existence, or one strongly rooted within an untamed ‘nature’. These variously represent or comment on ways-of-living-in-the-wetland, as well as highlighting distinctive wild ecological or climatic details. They also provide important cultural details, around place names and terminology for peatland activities that historically were hugely significant to the communities that made use of them.

Our wetlands, therefore, offer a powerful lens to look at climate change – especially when combined with archaeological, cultural and historical information, that highlights their ecological and human significance. 

Nicki Whitehouse, Althea Davies and Tom Gardner