The lowland heath that is present today across Britain and Europe has evolved as a result of climate change and historical human management, the development of agriculture and land use has effected the vegetation and habitat of lowland heath throughout the ages, affecting both establishment and decline.
Influence of Humans
The first signs of heathland came with the retraction of ice sheets at the end of the last ice age, approximately 14,000 years ago tundra type of vegetation began to establish as ice melted and moved, over the next 4,000 years these species developed and spread over Britain and Europe. Tundra vegetation is typically low and slow growing having adapted to survive the harshest and most hostile of conditions, these characteristics can still be seen today in some heathland plants although adaptations to new climates and soils has changed the vegetation significantly.
As the climate continued to warm new species emerged and the landscape of Britain quickly changed, from 10,000 – 6,000 BP the domination and succession of vegetation to forest over-competed with heath vegetation and soon most of Britain was covered in dense forest; lower growing species were shaded out and only existed in open glades and woodland margins.
The birth of heathlands came during Neolithic times (6,000 – 4,000 BP), Neolithic man turned away from hunter-gatherer survival and began the domestication of plants and animals which lead to management of land and the beginnings of agriculture. During this time large areas of forest and woodland were cleared, most probably by the use of fire, as technology had not yet developed tools suitable for large-scale tree clearance.
The cleared land was used for growing crops for food, in the early days of agriculture man did not have the knowledge to be able to sustain crop growth and so every 20-25 years the soil would be depleted of nutrients and farmers were forced to move to another area and begin the process anew.
The land now became open to succession with the desertion of agriculture and trees began to re-establish, if the area were totally neglected succession would continue to permanent woodland cover. In other cases the land was used to graze livestock such as cattle, sheep and pigs; this prevented the dominance of tree species and allowed for heathland species to establish. Grazing by livestock is a key contributor to the development of heathlands, as we know them today.
By the start of the Bronze Age heathlands had become well established, the growth of population and immigration of people from Europe changed the way that people were living. Human settlements started to appear on more nutrient rich grounds and the development of agriculture there showed a higher productivity and yield of crops than on the previously farmed nutrient poor soils of the Neolithic times. The abandonment of heathland allowed for further domination by heath species.
Despite their reduced popularity, heathlands were still utilised by local people for the resources they could provide and the small scale, low impact management continued to encourage specialised species to develop.
Heathland management continued with little change until the start of the 17th century, by this time much technological advancement allowed for agricultural improvement to take place on barren lands. The enclosure of common lands by the authority of Acts of Parliament in the 17th and 18th Centuries allowed farmers to further develop fields systems and improve agricultural management,
This meant that “waste areas” such as heathlands could now be used for development and reclamation. This lead to a national decline as land is reclaimed for agriculture or abandoned as it became easier to transport and purchase goods rather than self produce, in which case succession to woodland began.
The industrial revolution saw dramatic decline to heathland, as thousands of hectares were lost to other forms of management and industrial growth. Increased agriculture and forestry as well as large-scale extraction of sand and gravel only added to the reduction of lowland heath habitats.
Of all the heathland habitats present in Britain in1800, only 18% still exists today.
The heathland landscape was considered of little importance or interest to the growing economic society that thrived after the industrial revolution, however it was an ideal setting for military manoeuvres and army camps took up residence on heathlands from the late 18th century. Evidence of this can still be seen of this all over lowland Britain today as many of the military stations have continued to exist and grow on heathland sites.
Today heathland is of significant conservational importance due to its decline and continued threat from human activities. Most are now designated SSSI or SAC with some also coming under SPA designation if certain birds are present at the site.
Heathland sites are now more fragmented than ever with small-localised habitats, 82% of all sites designated are considered as being in unfavourable condition. Heathland is a key issue in conservation today and its future hangs in the balance, and it may already be too late as only 58,000 ha exist today in the UK and most of these are in very poor condition. However the Biodiversity Action Plan (BAP) aims to improve existing sites and establish a further 6,000 ha of heathland in lowland Britain.
The Physical Environment
Lowland heath has developed as result of human interference; its survival has also depended on several physical factors that have contributed to its current status. Heathland is restricted by climate, despite it frequenting well drained soils it cannot thrive on continental climates with dry summers and cold winters as water availability is just too low, preferring a more moist “oceanic” climate, of which Britain is ideal. The high precipitation levels in the UK allow heathland to continue and strengthen.
Lowland heath predominantly occurs on acidic, free-draining, sandy soils with poor nutrient availability. The underlying geology varies but in the south and east, heathland soils sit upon sands and gravels and sometimes clays: E.g. heathland found in the Thames Basin is made up of tertiary sands over London clay. The presence of clay can help to trap water, creating microhabitats within the heath and increased moisture spurs an increase in species diversity especially with regard to invertebrates. Although heathland may seem uniform and similar in appearance, variation in geology and soils produces different habitats and communities.
There are three types of heathland, wet, dry and humid; wet heath occurs in areas where the water table is predominantly high throughout the site and water is readily available, dry heath occurs on very well drained soils and underlying rock formations and thus the water table remains consistently low. Humid heath is an intermediate of the two, experiencing both wet and dry conditions throughout the year.
Topography varies from one heathland to another, though predominantly rolling hills and varied mounds and valleys seem to provide the most opportune structure for varied wildlife. The hilly landscape creates high and low points with continual erosion of unstable loose sand deposits on the slope; this helps new species to develop and provides ideal conditions for some specialised species that require base open ground.
Hills and valleys also allow minerals to be washed down from higher ground, possibly creating podzols and iron pans: areas capable of containing water, increasing the diversity of the habitat. Another factor that arises from varied slopes is the amount of light and shade varies depending on which face faces south, this allows for very different types of vegetation to occur in close proximity to one another. Although there is often a lot of slope on lowland heath it can also experience areas of very flat terrain, and even in the hillier areas there it does not compare to the heathland of highland Britain that occurs at high altitudes and on much larger, steeper slopes.
Plants and Animals
Vegetation
Lowland heaths are dominated by the presence of ling heather (Calluna vulgaris); this is the most common heathland plant and is the sole species of its Genus. Ling is a small perennial shrub growing 20-50cm tall. Small scale like leaves have adapted to conserve moisture and reduce transpiration rates. The roots spread radially to absorb moisture quickly and the evergreen leaves allow the plant to produce food all year round. Ling heather also benefits from a symbiotic relationship with mycorrhiza in which the plant is aided with nutrient absorption and the fungi receive sugars.
Ling has developed and adapted to withstand fire, a popular historical form of management and one still practiced today, its ability to withstand controlled fire conditions and show positive regeneration afterwards has contributed to its success on heathlands. The seeds can lay dormant for many years in the soil and fire open up the area to light allowing new growth to commence.
Ling heather is a valuable food resource for a wide range of species including sheep, deer, grouse, heather beetle and the larvae of numerous species of Lepidoptera.
Ling is also accompanied often by Bell Heather (Erica cinerea) a low growing shrub with needle like leaves. It is less woody and more slender than Ling and often uses other heathers and gorse for support and grow tall in close proximity with higher vegetation. Bell Heather forms dense uniformed swards and accompanies other heathers in providing food and protection for heathland animals.
Common Gorse (Ulex europaeus) is a spiny evergreen shrub that can reach up to 2 meters, the stem is hairy and leaves have adapted to low water availability by tuning to spines, which reduce water loss rates. Common Gorse is also a fire climax plant; it burns easily but regenerates well from the roots after a fire.
The bright yellow flowers bloom in mid summer attracting hundreds of invertebrates to feed on the sweet nectar; the plant emits a sweet coconut-like fragrance to attract insects. Stonechats (Saxicola torquata) use the higher branches to sing and Dartford Warblers (Sylvia undata) are attracted by the abundance of insects and will nest when gorse occurs in dense growth with heather. In the south of England you will also find Dwarf Gorse (Ulex minor), which as its name suggests is much smaller than Common Gorse, reaching up to a metre tall.
Invertebrates
5,000 species of invertebrate occur on heathland in the UK, with a variety of butterflies, wasps, bees, beetles, spiders and ants. Digger wasps and solitary bees are common to heathland because of the patches of open sandy ground that occurs throughout.
Sand wasps (Bembix spp) construct tunnels in bare patches of ground in which they lay their eggs, the tunnels are then sealed stocked with food (normally spiders or caterpillars but dependant on prey species choice) which is eaten when the eggs hatch.
Potter Wasps (of which there are over 200 Genera but are most often considered to be of the Subfamily: Eumeninae), construct pots from the soil which they stick to heather branches. The pots are filled with eggs and paralysed prey and then sealed.
The Silver Studded Blue Butterfly (Plebeius argus) is a common inhabitant of heathlands, feeding on ling, Bell Heather and Gorses. Males display bright silvery-blue wings, whilst the females are a dimmer brownish hue, both sexes display the characteristic metallic spots on the hind wing that the species is known for. The butterflies rely on short, sparse vegetation and prefer the open canopy of recently burnt heath.
Birds
Heathland provides food and shelter for both migratory and native birds; there are several species of particular association with heathland over other habitats. Nightjars (Caprimulgus europaeus), are African migratory birds that arrive in spring to nest, they inhabit lowland heaths as well as open woodland and young conifer plantations: theses birds prefer open patches of heath and the small clearings that occur there.
Both sexes are well camouflaged for ground nesting, displaying mottled grey to brown hues, the body is sleek and pointed and well adapted to hunting prey on the wing. Nightjars feed at dusk, dining on the abundant invertebrates that arrive on heathlands over the warmer months.
A popular bird of lowland heath is the Dartford warbler (Sylvia undata), it has suffered decline in past years but populations are slowly begging to rise again with the milder winters that Britain has been experiencing and designative protection from the government (however still confined to southern heaths).
Dartford warblers are small birds with long tails, the coats are brown above with pink below and the both sexes have similar coats with the male exhibiting brighter shades. Most warblers fly to Africa in the autumn, Dartfords survive from the protection provided by dense stands of evergreen heather and gorse, the vegetation provides a barrier from snow, rain and cold winds and the canopy is inhabited by enough insects to make survival possible.
These birds benefit from managed heath with varied ages of stands providing continual protection.
Stonechats (Saxicola torquata) though not restricted to heathland, are frequent inhabitants nesting in dense patches of gorse and heather. The males also require higher local vegetation on which to sit and call this is normally an upper gorse or scrub branch. This species benefits from some scrub present and feeds on fruits as well as insects.
Reptiles
Heathlands can be home to all six native species of reptile, four of them can be found in other habitats around the country, but two species are restricted to heathland and its surrounding boarders.
The Smooth Snake (Coronala austriaca) is a pretty rare species found only in the lowland heath of Dorset, Hampshire and Surrey. The skin is a camouflaged grey-brown colour with two rows of small, dark markings don the length of the body. Smooth snakes grow to 60-70cm long and feed on other heathland reptiles such as common lizards (Lacerta (zootoca) vivipara) and slow worms (Anguis fragilis), as well as small mammals. These snakes will bite to protect themselves but have no venom: they predate through constriction. Smooth snakes rely utterly upon well-managed, mature heathland with plenty of hiding places in which to sun itself.
Sand Lizards (Lacerta agilis) are another heathland dependant and are scarce in the UK occupying small areas in Dorset, Hampshire, Surrey and Lancashire. Their survival is closely linked to managed heathland especially where bare patches of sand are created, on which they can dig tunnels for their eggs. The eggs remain buried for several months and the open sand helps to keep the eggs warm. Sand lizards are distinctively stockier than the common lizard with a deep short head and bulkier frame. Both sexes are marked with a mix of black, brown and cream spots running down the back, in spring males are bright green whilst females remain a pale brown, sandy colour.
References:
http://www.butterfly-conservation.org/species/bdata/butterfly.php?code=sib
http://www.dorsetforyou.com/index.jsp?articleid=336264
http://www.surreycc.gov.uk
http://home.freeuk.com/offwell/whatis.htm
http://www.ukbap.org.uk/ukplans.aspx?ID=15
http://www.surreyheath.gov.uk/tourism/AboutSurreyHeath/heritage.htm#camberley
http://www.wildlifetrust.org.uk/cheshire/heathland.html
http://www.countrysideinfo.co.uk/historic.htm
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