Mendip Hills - Ecology

Ecology

Three nationally important semi-natural habitats are characteristic of the area: ash–maple woodland (Fraxinus spp. and Acer spp.) often with abundant small-leaved lime (Tilia cordata), calcareous grassland and mesotrophic grassland.

Much of the Mendips is open calcareous grassland, supporting a wide variety of flowering plants and insects. Parts are deciduous ancient woodland and some has been used intensively for arable agriculture, particularly since World War I. As the demand for arable land in Britain declined, some areas were returned to grassland, but the use of fertilisers and herbicides has reduced its biodiversity. Grazing by rabbits (Oryctolagus cuniculus), sheep (Ovis aries) and cattle (Bos taurus) maintains the grassland habitat.

Of the many bird species found in the Mendips the Peregrine Falcon (Falco peregrinus), which has gradually recolonised the area since the 1980s, is particularly significant. It breeds on sea and inland cliffs and on the faces of active and disused quarries. The upland heaths of the west Mendips have recently increased in ornithological importance, due to colonisation by the Dartford Warbler (Sylvia undata), which can be found at Black Down and Crook Peak. In Britain, this species is usually associated with lowland heath. The woodlands at Stock Hill are a breeding site for Nightjars (Caprimulgus europaeus) and Long-eared Owls (Asio otus). The Waldegrave Pool, part of Priddy Mineries, is an important site for dragonflies, including Downy Emerald (Cordulia aenea) and Four-spotted Chaser (Libellula quadrimaculata). Waldegrave Pool is the only Mendip breeding site for Downy Emerald dragonflies. In 2007 the first confirmed sighting of a Red Kite (Milvus milvus) on the Mendips was made at Charterhouse.

A range of important small mammals are found in the area, including the Hazel Dormouse (Muscardinus avellanarius) and bats. The hazel dormouse is restricted largely to coppice woodland and scrub, while the bats, including the nationally rare lesser (Rhinolophus hipposideros) and Greater Horseshoe Bats (Rhinolophus ferrumequinum), have a number of colonies in buildings, caves, and mines in the area. A rare and endangered species, the Greater Horseshoe bat is protected under the Wildlife and Countryside Act 1981 and is listed in Annex II of the 1992 European Community Habitats Directive. Amphibians such as the Great Crested Newt (Triturus cristatus) have a wide distribution across the Mendips and are often found in flooded disused quarries.

Several rare butterflies are indigenous to the area, including the nationally scarce Pearl-bordered Fritillary (Boloria euphrosyne), Duke of Burgandy (Hamearis lucina), and White-letter Hairstreak (Satyrium w-album). The Large blue butterfly (Maculinea arion) became extinct in the hills in the late 1970s, since when a research project has been undertaken into its ecology and reintroduction. The White-clawed crayfish is also nationally rare and is a declining species with small populations in a tributary of the Mells River and the River Chew.

The dry stone walls that divide the pasture into fields are a well-known feature of the Mendips. Constructed from local limestone in an "A frame" design, the walls are strong yet contain no mortar, although many have been neglected and allowed to disintegrate, replaced or contained by a mix of barbed wire and sheep fencing. These dry-stone walls are of botanical importance, as they support important populations of the nationally scarce Wall Whitlowgrass (Draba muralis). Amongst the plants which occur in the area are the Cheddar pink (Dianthus), Purple gromwell (Lithospermum purpurocaeruleum), White rock-rose (Helianthemum apenninum), Somerset hair-grass (Koeleria vallesiana), and Starved Wood-sedge (Carex depauperata).