Skip to content Skip to navigation

3.2 Biodiversity and Geodiversity

Chedder Gorge © Mendip Hills AONB Unit

3.2.1 Geology, soil type as well as human influences such as agriculture and mining have resulted in the Mendip Hills distinctive landscape features, and give rise to the variety of habitats and their dependent flora and fauna.

3.2.2 Over millennia, humans have reduced the cover of woodlands, creating open habitats such as grassland. Land enclosures enabled farmers to create more agriculturally productive grasslands from heathland. In the more recent past, technological innovations have enabled significantly increased the agricultural yields of grassland, which has also changed the character of grassland habitats in particular. Species rich grassland habitats are now increasingly rare and only occur where low intensity management takes place and on inaccessible areas difficult to plough.

3.2.3 Habitats of particular importance in the Mendip Hills are heathland, acid grassland, calcareous grassland, neutral grassland (meadows), calaminarian grassland (occur on lead mined spoil heaps), purple moor grass and semi -natural ancient woodland with typical Mendip species, ash and lime.

3.2.4 The spoil heaps from lead mining provide distinctive Mendip habitats due to the high levels of lead, cadmium and zinc that are toxic to most plants. These metal rich habitats contain species such as spring sandwort, alpine penny cress and sheep’s- fescue.

3.2.5 Limestone crags and cliff faces are home to many plant species including the rare and protected Cheddar pink (the flower of Somerset) in Cheddar Gorge. The thin limestone soils support grassland insects and invertebrates. Many of the caves are roosting and hibernation sites for bats.

3.2.6 The Mendip Hills AONB contains many sites designated for their biodiversity, including the European designations:

3.2.7 There are also 27 sites designated for their national importance as a Site of Special Scientific Interest (SSSI). Ninety six percent of the 2712 ha designated as SSSI is in favourable or unfavourable and recovering condition. Local Wildlife Sites act as buffers, stepping stones and corridors for these nationally designated wildlife sites.

3.2.8 Section 41 of the Natural Environment & Rural Communities Act 2006 list of species of principle importance found in England identified as requiring action under the UK Biodiversity Action Plan continues to be regarded as conservation priorities under the UK Post-2010 Biodiversity Framework. A significant number of these are found in the designated sites listed in 3.2.6.

3.2.9 The area is noted for its geodiversity, with a large range of rock types ranging from Devonian to Jurassic exposed in many natural rock outcrops and quarries.

3.2.10 Carboniferous limestone has created the Mendip karst landscape, a terrain formed as percolating rainwater dissolves the rock, forming gorges, depressions, underground drainage and caves. Streams emerge at the foot of the hills where the limestone meets less permeable rock. Many of the geological features are designated SSSI and or Local Geological Sites.

3.2.11 The ‘Netherworld’ of the Mendips is significant and cave exploration is on going. In 2012 the largest Mendip cave was discovered and has some of the best stalactites and stalagmites in the UK.

3.2.12 The British Geological Survey and Mendip Cave Registry and Archive are sources of information. Mendip quarry companies have invested in proactive relationships with the public offering opportunities to visit and the Somerset Earth Science Centre at Moon Hill Quarry has initiated and partners a number of geology related projects including Mendip Rocks and Quarry Faces in the AONB that promote research and learning.

3.2.13 Protected landscapes have been identified (see 2.2.0) to deliver more resilient and coherent ecological networks, healthy and well functioning ecosystems which deliver multiple benefits for people and wildlife. Building the resilience of ecological networks will enable the ecological network to respond to climate change.

3.2.14 Work to understand the current state of the network has been on going for some years with support from the AONB Partnership. Somerset Wildlife Trust continues to map distribution of all remaining habitats in the Mendip Hills National Character Area (NCA). Initial ecological networks have been identified which will continue to be refined as survey reveals new areas of priority habitat. The focus will then move to identification of priority restoration areas within the ecological networks and identifying monitoring indicators to see how different species respond to strengthened networks. This work will further assist management advice and targeting of Environmental Stewardship schemes and development of a Mendip Hills Nature Improvement Area.

3.2.15 In addition it will also assist local authority’s duty under The National Planning Policy Framework (See 2.5.0 Drivers for Change and 3.7 Development and Transport). This states that planning policies and decisions should be based on up to date information about the natural environment and other characteristics of the area including an assessment of existing and potential components of ecological networks.


3.2.16 The pressing issue for biodiversity and geodiversity is loss of ecological network and geological features, condition and fragmentation of habitats due to changes in land use including energy crops, intensification of agriculture, new development and less resources for management.

3.2.17 There is a need to understand and recognise the geological importance of cave systems for their geological and biodiversity importance. Caves need to be protected from damage by land use e.g. pollutants in water run off, broken sewage pipes, soil erosion, tipping and infilling of swallets and inappropriate recreational use, and where use disturbs roosting bats.

3.2.18 Cave systems needs to be better understood with regard to water flow and water supply (See 3.5 Natural Resources) as was shown recently at Cheddar when sink holes became blocked and flood waters washed away part of Cheddar Gorge road and with the proposal for a fourth reservoir fed from the Mendip Hills.

Biodiversity and Geodiversity Objectives

BG1 Ensure that there is no net loss of characteristic habitats and species.

  • BG1.1 Ensure local input to updating of National Character Areas Statements of Opportunity and respond to any implications. Details
  • BG1.2 Build on improvements in Sites of Special Scientific Interest (SSSI) condition to date by moving SSSI land from Recovering to Favourable condition Details

BG2 Promote a landscape scale approach to the conservation and expansion of coherent and resilient ecological networks within and adjoining the AONB.

  • BG2.1 Explore potential of a locally determined Nature Improvement Area for the Mendip Hills NCA. Details
  • BG2.2 Demonstrate best practice by the use of pilots and case studies Details
  • BG2.3 Support farmers and land managers to increase land in the Mendip Hills covered by agri-environment schemes where possible Details

BG3 Increase awareness and monitoring of the biodiversity resource of the Mendip Hills AONB so that it is sufficiently understood to continue to guide the successful conservation of the characteristic habitats and species.

  • BG3.1 Promote ecological network information available for the Mendip Hills in an easily accessible form Details

BG4 Promote a holistic approach to implementing the AONB Management Plan objectives, National Character Area Statements of Opportunity and a locally determined Nature Improvement Area’s objectives.

  • BG4.1 Explore potential of a locally determined Mendip Hills NIA for the Mendip Hills NCA incorporating Management Plan objectives and NCA opportunities Details

BG5 Recognise and celebrate geological sites and features of the Mendip Hills AONB to ensure the successful conservation both of the geology and wildlife habitat they provide.

  • BG5.1 Organise annual Mendip Rocks! festival Details
  • BG5.2 Implement Discovering Black Down ‘what lies beneath’ school and youth group caving activity/learning programme. Details
  • BG5.3 Develop a Mendip Rocks Framework Plan that identifies and implement priorities for the conservation and interpretation of geological sites and features. Details
  • BG5.4 Produce two geological trails in the AONB Details

BG6 Increase awareness of the Mendip Hills geology, particularly cave systems in relation to the importance they play in water management and water supply.

  • BG6.1 Linked with BG5.2 produce information on the importance of the Mendip Hills geology in providing a water resource Details