Raised bog

Raised bogs are localised, often isolated domes of peat rising several meters above surrounding land and fed exclusively by rainfall and other forms of precipitation (ombrotrophic). Like blanket bogs, raised bogs are also waterlogged, nutrient poor and acidic, with few plant species accustomed to such conditions.

Cranberry (Vaccinium oxycoccos), bog rosemary (Andromeda polifolia) and cottongrasses (Eriophorum spp.) can be found among Sphagnum mosses on a raised bog, which create a unique surface topography of hummocks and bog pools. Carnivorous sundews (Drosera spp.) butterworts (Pinguicula spp.), bladderworts (Utricularia spp.) and other bog species can be found here, along with invertebrates such as midges (Nematocera spp.), mosquitoes (Culicidae) and the large heath butterfly (Coenonympha tullia).  

Raised bogs can be divided into distinct types based on their formation and location. A basin bog is a typical raised bog that forms in a shallow basin that is steadily infilled by fen peat and then bog peat. In deeper, steep-sided basins, a floating raft will typically form, which may eventually thicken to form a dome over the trapped water body. Flood-plain raised bogs and estuarine raised bogs are formed on floodplains of rivers and estuaries, respectively. Both types of bog will typically contain sediment layers from river or marine flood events in the deeper layers of the peat. Raised bogs are therefore a climax community, following succession from water bodies through fens to an ecologically stable raised bog.  

Raised bogs are often surrounded by laggs - wet areas that receive their water from adjacent uplands as well as the domed centre of the raised bog itself. Laggs have a higher nutrient content and are identifiable by vegetation typical to fens, such as tall sedges.  

In the UK, raised bogs are mainly found in lowlands where up to 10 m of peat has accumulated over 10,000 years. Raised bogs are found across wetter parts of the UK, particularly in central Scotland, Northern Ireland, the Solway region and Morecambe Bay. 

Degraded and drained raised bogs can look very different from healthy bogs. Signs of erosion and fragmentation are often visible. Vegetation is impoverished: Sphagnum moss that is characteristic of healthy bogs is scarce or absent, and grasses and shrubs such as purple moor grass, heather and hare’s tail cottongrass begin to dominate the drier surface. The hummock/pool topography characteristic of bogs is lost, and over time, degraded raised bogs can begin to resemble heathlands. In more extreme cases, the vegetation is completely absent and dark, bare peat is exposed on the surface. 

The exent of raised bog was much greater in the past, as most raised bogs in the UK have been lost due to peat extraction, drainage and afforestation. Read more about threats to peatlands. 

Quaking bog

Quaking bogs (also known as ‘schwingmoors’) develop as Sphagnum moss grows over shallow, acidic lakes or bog pools. A thin layer of peat forms and floats on the surface of the water. It is possible to feel the bog quake when walking over its surface, which gives them their name. Rare species, such as the great fen raft spider and the marsh fritillary butterfly are found here.  

Quaking bogs are relatively rare habitats, with examples found in the Meres and Mosses of the northwest Midlands of England, and parts of Wales. 

See an example of a Welsh quaking bog among other types of peatland in the video below.