Heath, bog, mire and species-rich rush pasture mosaics

The main remaining areas of mosaic habitats include:

• Extensive areas of wet and dry heath, upland acid grassland, bog and mire on unenclosed Dartmoor and Exmoor.
• Complex mosaics of species-rich rush pastures, mire, wet heath and wet woodlands on the wet soils of north Devon, enclosed Dartmoor and the scarp slopes in east Devon and the Blackdown Hills. Often known as Culm grassland in north Devon and as spring-line mires in the Blackdowns. These grade into dry wildlife-rich grasslands on drier soils – see Wildlife-rich grasslands.
• Mosaics of heath, mire, lowland dry acid grassland, bracken and scrub on the South West Dartmoor Downs between Plymouth and Tavistock, including areas such as Roborough Down and Crownhill Down.
• Mosaics of dry heath, wet heath, valley mires and scattered trees and scrub on the Pebblebeds, Bovey Basin, Haldon and east Devon ridges and plateaux (including the Blackdown Hills).
• Smaller areas of heath on the coast and wet heathy grasslands in south Devon around Andrews Wood SSSISite of Special Scientific Interest More.

Devon’s distinctive yellow and purple heathlands are found on nutrient-poor, acidic podzol soils and wet acidic gley soils. The largest areas of heathland are found on Dartmoor and Exmoor. Other key areas are the Pebblebed Heaths, the eastern Devon plateaux and ridges (Trinity Hill, Fire Beacon Hill and Gittisham Hill), Haldon and the Bovey Basin.

Heathland is also found along both Devon coasts (west of Bolt Head, north of Saunton and a small area at Berry Head) and as part of the north Devon Culm grassland mosaic.

Heathlands are defined by the dominance of dwarf shrubs. Characteristic speciesA group of similar organisms that can breed and exchange gen... More of Devon’s heaths include bell heather, heather, western gorse and bristle bent. Wet heathland develops where drainage is impeded. Bell heather is replaced with wetland-loving species such as cross-leaved heath, purple moor-grass, cotton grass, deer grass and bog mosses (sphagnums). At higher altitudes on Dartmoor and Exmoor species such as bilberries become more common. 

The plant communities on these heaths are only found in the wet and mild western fringes of Europe and Devon’s heathland is internationally important. Heathlands aren’t botanically rich, but the mosaic of habitats and structural diversity support specialist species. This mosaic includes:     

Bare areas of sand and soil, especially on warm south-facing slopes: Important nesting and basking areas for invertebrates such as bees, wasps, ants and snakes such as adder and smooth snake. The only site in England for the narrow-headed ant is Chudleigh Knighton Heath.

Open areas for flowering plants: Heath lobelia was once common on the wet heaths around Shute in east Devon but is now only found at one site and Andrew’s Wood in the South Hams. Violets are an important foodplant for rare fritillary butterflies.

Young heather shoots: An important food source, including for silver-studded blue butterfly caterpillars.

Mature heather, gorse and patches of scrub and bracken: Important shelter, nesting and feeding habitat for invertebrates and birds such as stonechat and Dartford warbler. Open ground between scrub provides safe ground-nesting sites for species such as nightjar, tree pipit, whinchat and meadow pipit. Bracken provides important shelter for rare fritillary butterflies.

Scattered trees: Provide song posts for birds such as tree pipits.

Valley mires, pools and wet runnels: Provide habitat for dragonflies and damselflies, sundews including rare species such as southern damselflies and scarce blue-tailed damselfly.

Other Devon Species of Conservation Concern found on heaths include the bog bush cricket – other examples to be added – see the Species Spreadsheet.

There is more information on plant communities in the LNRS Habitat Classification Table and the Lowland Heathland, Upland Heathland and South West Dartmoor Downs LNRS papers. See Find out more below.

Historically, heathlands were maintained for their economic value. They provided important rough grazing for small numbers of cattle, ponies and sheep. Turf was cut for fuel (for example from Stockland Turbaries in the Blackdown Hills), gorse was used to feed livestock, bracken was used for bedding and heather was used for thatch. They were often burnt (swaled) to provide new soft growth for grazing livestock. All Devon’s heaths have historical remains of life dating back to the Bronze Age and these activities stopped them reverting to woodland.

However, huge areas of Devon’s heaths have been lost. The former open commons on the east Devon and Blackdown Hills plateau and ridges were enclosed in the 19^th century and only a few remnants survive. Heaths across Devon’s lowlands and uplands were planted with conifer in the early 20^th century. Areas of heath over china and ball clay at Lee Moor and the Bovey Basin have been lost to quarrying. Changes in farming practices over the centuries alongside impacts as a result of the industrial revolution (mining, air quality etc) have had a significant impact on landscapes and vegetation resulting in the decline or loss of some species. For example species recorded as widely scattered across south-west Dartmoor commons such as heath fragrant-orchid and field gentian have almost disappeared.

After the 1947 Agricultural Act, farming in areas like Dartmoor and Exmoor intensified, with more grazing, drainage and re-seeding. Heathland and mires were lost and large areas of drier acid grassland have developed across much of Dartmoor and Exmoor. Heathlands have been undergrazed in parts of the uplands. This has led to areas on steeper slopes becoming dominated by gorse, scrub and bracken with other areas now dominated by purple moor-grass (Molinia caerula). See Key pressures and opportunities below for more information.

Many lowland heaths have been lost to scrub and secondary woodland as they’re no longer needed by farmers for rough grazing. Most are now managed as nature reserves by organisations such as Devon Wildlife Trust, the RSPB and Clinton Devon Estates. Heathland remnants in the Blackdown Hills near Stockland and Kilmington are being restored and managed by local residents and parish councils. 

There is more information in the Lowland Heathland, Upland Heathland and South West Dartmoor Downs LNRS papers. See Find out more below.

In Devon, mires (or fens) are generally  found on wet, very acid soils, especially gley soils. They’re incredibly valuable for wildlife, supporting both widespread and specialist species.  Most receive water from seepages, springs and small streams and they would have once been very common across Devon. However the mass production of drain tiles and pipes in the early 19^th century led to huge areas of Devon’s wet soils being more efficiently drained and mires were lost. By 1939, between 50% and 75% of Devon had undersoil drainage.

A concentration of mires remains on the scarp slopes of east Devon and the Blackdown Hills where permeable greensand rock overlies impermeable mudstone and spring-lines have developed. The largest surviving sites are Hense Moor and Southey and Gotleigh Moor which, along with Bolshayne Fen (near Colyton) and Bulmoor Pastures, are designated as SSSIs. There are also small areas of spring-line mires along the coast from Sidmouth to the Dorset border.

Valley mires are found on Dartmoor and Exmoor as well as in the Pebblebed and Haldon heaths. They often develop in wet, shallow valleys and support a wealth of wildlife. Dartmoor valley mires support particularly rare species such as bog hoverfly and breeding birds such as grasshopper warblers, snipe and curlew (now very rare). Wetland flushes also occur on Dartmoor and Exmoor where water seeps from springs.

The only known spring-fed mire in south Devon is Wolborough Fen SSSI in Newton Abbot. 

These spring-line mires, valley mires and flushes are fed by well-oxygenated and mineral-enriched water and can be very species-rich. Rare species can include greater sundew, fir club-moss, and broad-leaved cotton grass, fen fragrant orchid and marsh helleborine. Characteristic species in more acidic mires include bog mosses (sphagnums), cotton grass, purple moor-grass, cross-leaved heath, bog asphodel and common sundew. Some areas can have devil’s-bit scabious and meadow thistle, which are characteristic of species-rich rush pastures (see below). Southern damselflies were once found on the Blackdown Hills spring-line mires but haven’t been seen since the 1960s (other than a failed re-introduction project) Add more on other species? possibly split up as for heaths?

There is more information on plant communities in the LNRS Habitats Classification Table (not yet added to the web) and the Lowland Fens and Upland Heathland and Bogs LNRS papers. See Find out more below. Add more on species? possibly split up as for heaths?

Blanket bogs are rain-fed wetlands which form on peat soils that are generally more than 40cms deep. The peat layer isolates vegetation from ground water to create wet, very acid and very nutrient-poor conditions that support species such as bog mosses, cross-leaved heath, cotton grasses and bog asphodel. Bog pools can also form on the blanket bog.

Blanket bog is extensive on the higher parts of Dartmoor, but less extensive on Exmoor. There is one raised mire in Devon, at Tor Royal Bog.

Blanket bog is an important carbon store and healthy bogs also absorb carbon. However, over the centuries blanket bog on both Dartmoor and Exmoor has been affected by activities such as peat cutting, land drainage, agricultural improvement and unsustainable grazing and burning practices. More recently it has been affected by climate change and atmospheric nitrogen and ozone pollution. As a result, only a fraction of the blanket bog is hydrologically functional and in good condition. Restoring and rewetting these areas are now conservation priorities and considerable amounts of money are being invested to achieve this. 

Peat is partially decomposed vegetation. In the rainy uplands of Dartmoor and Exmoor, high rainfall leaches minerals from the soil creating an impermeable layer (known as an iron pan) which prevents drainage. The resulting water-logged soils are perfect for bog mosses (sphagnum). These mosses and other plants decompose very slowly due to lack of oxygen and, over 1,000s of years, form a deep layer of peat.  

Focus Species include breeding dunlin, bog spiders and bog hoverfly.

There is more information on plant communities in the LNRS Habitats Classification Table and the Upland heaths, mires and bogs LNRS paper. See Find out more below.

Devon is a stronghold for species-rich rush pastures (also known as purple moor-grass and rush pasture or fen meadows). This is a UK priority habitat which can occur as mires get drier or as wet, acidic grasslands get wetter. Rush pastures are found on damp, acidic, nutrient-poor gley soils. They are found in complex mosaics of habitat with wet heath, mires and wet woodland. These habitats grade into each other, making mapping difficult.  

Species-rich rush pastures are found on the wet, acidic Hallsworth and Wickham soils of the Culm Measures between Dartmoor, Exmoor and the Cornwall border, where the mosaic of wetland habitats is known as Culm grassland. They’re also found on the wet Laployd soils in enclosed areas of Dartmoor, where the mosaic of habitats is sometimes known as Rhos pasture. There are also small areas on Hense soils in the scarp slopes mires of the Blackdowns and east Devon, where mires and wet pastures grade into each other.  

This habitat is characterized by tussocks of purple moor-grass (Molinia). The most species-rich communities support meadow thistle, devil’s-bit scabious (the foodplant for marsh fritillary butterfly and narrow-bordered bee hawk-moth), heath spotted-orchid, bog asphodel, creeping willow, meadowsweet, greater bird’s-foot trefoil, water mint and a variety of sedges. Rarer plants include round-leaved sundew, pale butterwort and lesser butterfly orchid. Bog mosses are often found, and open pools support marsh St John’s-wort, bogbean, marsh pennywort, bog pondweed and other aquatic plants. 

Focus Species include marsh fritillary and narrow-bordered bee hawk-moth (which require devil’s-bit scabious), the tormentil globetail hoverfly, lesser butterfly orchid and grasshopper warblers. Southern damselflies have been recorded in a few Dartmoor Rhos pasture sites such as Tor View Moor near Whiddon Down.

To be finished during the consultation in discussion with NE and with latest CWSCounty Wildlife Site More data

Area

xxxx

SSSIs

Unfavourable declining: Maiden Down

County Wildlife Sites

To be finished during the consultation in discussion with NE and with latest CWS data

Area of heathland

It’s hard to establish the exact extent of upland heath as mosaic habitats are difficult to map.

The Nature of Dartmoor report: ~  11,500ha of heather moorland on Dartmoor

JNCCJoint Nature Conservation Committee More citation for the SACSpecial Area of Conservation More states that 40% of the Dartmoor SAC is upland heath = 9,263 haHectare: an area of 10,000 square metres, or 2.47 acres More.   

Exmoor National Park estimates that there is ~ 7,000ha of upland heath and 1500ha of lowland heath across Exmoor (Devon and Somerset). The  JNCC states that it accounts for 83% of the SAC =  8,856ha. 

Exmoor lost 20% of its upland heath between 1940 and 1980 as a result of government funded agricultural improvement schemes. However, Dartmoor lost much less of its upland heath during the same period.

Area of mire

Estimating the extent of mire is hard as mapping techniques have varied. An unpublished DNPADartmoor National Park Authority More analysis from 2020 suggested that there may be 5,400ha of mire on Dartmoor’s commons, moorland and newtakes. National England’s National Vegetation Classification analysis for the North and South Dartmoor SSSIs gives ~  402ha.

Area of bog

It’s hard to estimate the area of bog as some is mapped as blanket bog, some as wet heath and some as Molinia mire.

Dartmoor:  ~ 3,432ha of blanket bog + 7,848ha of degraded blanket bog (DNPA 2020). There is over 17,500ha of peat soils more than 40cms deep on Dartmoor (Luscombe et al 2016). 

Exmoor:  ~  480ha of quality blanket bog and an additional 4,400ha of degraded and mostly Molinia dominated blanket bog (ENPA 2001). 

SSSIs / SAC

Dartmoor / Exmoor SSSIs…….

Dartmoor SAC covers 23,158ha and includes areas of upland heath, valley mires, flushes and blanket bog. It has three SSSIs: North, South and East Dartmoor.

Exmoor SAC covers 10,670ha and includes mosaics heath, mire and blanket bog. There are four SSSIs on Exmoor (Devon and Somerset) which include upland habitats and around 60% of these are in the SAC. The 4 Exmoor SSSIs are North Exmoor, South Exmoor, Exmoor Coastal Heaths and West Exmoor Coast and Heaths.

Condition of bogs

The University of Exeter’s research indicated that of the 17,510ha of peat over 40cm in depth only 360ha (0.8%) was intact and hydrologically functional. They also identified around 2,289ha which should form the primary focus for restoration. (Luscombe et al 2017).

Significant areas of Dartmoor and Exmoor have been in environmental schemes for approaching thirty years and despite their detailed management prescriptions the figures above show that the vast majority of these heathlands are not in ‘favourable condition’ as determined by Natural England’s Assessments. 

To be finished during the consultation in discussion with NE and with latest CWS data

Area

SSSIs:

Favourable or unfavourable recovering:

Unfavourable:

To be finished during the consultation in discussion with NE and with latest CWS data

Area (JNCC, 2008):

In Devon and Cornwall only 8% of that present in 1900 remains, with 62% of sites and 48% of the total area being lost between 1984 and 1991 

Devon and NE Cornwall Culm –  530 purple moor-grass and rush pasture sites = ,3981ha

Dartmoor, Rhos pasture – 400 sites = 1,000ha

Blackdown Hills –  90 sites = 300ha

SSSIs:

Found in 26 SSSIs=  1,081 hectares. Dunsdon Farm SSSI is also a National Nature Reserve.

Eight of these are also Special Areas of Conservation. Six culm Grassland sites are now DWT Nature Reserves, covering some 200 hectares. 

Found in small areas within five SSSIs on Dartmoor. 

Found in four SSSIs in the Blackdowns Hills:  Hense Moor, Ashculm Turbary, Southey and Gotleigh Moor and Blackdown & Sampford Commons.  There are also two Devon Wildlife Trust Nature Reserves.

Natural England’s Favourable Condition Assessment for Devon includes the category Fen, Marsh and Swamp – Lowland which includes Purple Moor-Grass Pastures but doesn’t specifically identify the condition of Purple Moor-Grass Pasture SSSIs.  

County Wildlife Sites (2024 data)

814 sites =  2,834 ha.

522 of these have been monitored between 2009 and 2022 and have been categorised as red, amber and green depending on their condition.

91 (17.4%) totalling 295ha (15.2%) were Red

283 (54.2%) covering 805ha (41.5%) were Amber

148 (28.4%) covering 838ha (43.2%) were Green.