Map 9. West Wiltshire and Cranborne Chase Downs

West Wiltshire and Cranborne Chase Downs

This Area comprises the open chalk downland  of the West Wiltshire Downs and some significant ancient woodland sites. The downlands have been used extensively for agriculture and have large arable fields, with areas of unimproved chalk grassland on the steep chalk scarps and ridges. Cranborne Chase in the far south is a relict of an ancient hunting forest and is one of the largest tracts of semi-natural woodland in the region, with a strong agricultural and woodland heritage.  It is designated as a SSSI and comprises a diverse mix of woodland and ground flora, as well as some of the richest sites for lichens in southern England. The ecologically rich waters of the Rivers Wyle and Ebble run through this area and form part of the internationally important River Avon Special Area of Conservation. These chalk rivers also support important water meadows, including those at Harnham south of Salisbury.

Priorities and opportunities for landscape-scale conservation

Priorities and opportunities for the landscape-scale conservation of priority habitats and species within each of the Strategic Nature Areas (SNAs) in Upper Thames Landscape Biodiversity Area. Priorities and opportunities are detailed under the Strategic Nature Area main priority habitat types present in this Area, with priorities for associated habitats and species listed underneath these:

1. Chalk Downland

     - Lowland calcareous grassland

     - Downland birds and butterflies

2. Rivers

     - Chalk rivers

3. Woodland

     - Lowland mixed deciduous woodland

     - Bats

1. Chalk Downland 

Lowland calcareous grassland

Species-rich calcareous grassland is present in many small, fragmented and isolated patches over much of the West Wiltshire and Cranbourne Chase downs. It is mainly restricted to the steep scarps and ridges of the downlands which, due to their topology, have largely avoided direct agricultural improvement. Many of the remaining fragments are designated as SSSIs or County Wildlife Sites and these form the basis of the Chalk Downland Strategic Nature Areas in Area 09. There is a need to expand and connect these areas to increase their resilience and buffer them from the effects of climate change and allow the movement of species through this environment. In addition the quality of existing semi-natural habitat needs to be improved where this is unfavourable. Priorities for this habitat include:

• Target priority areas identified through the Strategic Nature Area and Stepping Stones projects where the data suggest appropriate habitat creation or restoration can provide the best contribution to enhancing ecological connectivity and offer significant biodiversity gain.

• Use relevant options in Environmental Stewardship Schemes to implement / increase grazing on under-grazed calcareous grassland sites

Existing conservation projects and initiatives  

The ‘Stepping Stones’ project is a partnership project between the North Wessex Downs AONBs, Cranborne chase and West Wiltshire Downs AONB, Natural England and the Wildlife Trust. The project compiled detailed habitat data for over 125,000 hectares, representing the majority of the Wiltshire chalk landscape stretching from Calne and Marlborough in the north to Mere and Salisbury in the south. The project has established the degree of isolation of priority grassland sites by modelling existing ecological networks, it has used these modelled networks to Identify opportunity areas for increasing priority grassland connectivity, and has demonstrate how this model and associated datasets can be used to help target management and restoration on the ground within priority areas.

‘New Life for Chalk Downland’ Project – The Wiltshire Wildlife Trust’s New Life for Chalk Grassland project aims to help halt the loss of chalk grassland in Wiltshire by restoring grassland and reverting marginal arable land back to grassland. Encompassing around 158,990 hectares of land in southern Wiltshire, the project trialled new conservation techniques for the management of chalk grassland and encouraged farmers and landowners to take them up. It is important to maintain the relationships with landowners and grazing regimes put in place through the project and to look for opportunities to extend the grazing management to areas that can increase connectivity of chalk grassland across the downlands of southern Wiltshire and beyond. The reversion of arable land to calcareous grassland will not only increase biodiversity in these areas but will also increase the carbon storage potential of this land and further reduce the risk of agricultural and pesticide runoff into the Hampshire Avon system.

Agri-environment schemes – The area between Salisbury, Tisbury and Shaftesbury falls within the Dorset Downs and Cranborne Chase Higher Level Stewardship (HLS) Target Area, while the area between Salisbury Tisbury and Warminster falls within the Salisbury Plain and West Wiltshire Downs HLS Target Area. These represent areas where Natural England wishes to focus delivery of HLS to maximise environmental outcomes and value for money. Within these target areas nationally important areas for biodiversity occur including chalk grassland, wet grasslands besides streams, ancient semi-natural woodlands, wood-pasture and parklands, and the River Avon river system. The area is nationally important for its assemblages of farmland birds, butterflies (including the rare Duke of Burgundy), bats and scarce grassland fungi. Applications for HLS in these areas must include options to maintain/restore/create these habitats or provide habitat for the important species assemblages noted in these areas.

Downland birds and butterflies

The birds and butterfly species that characterise chalk downland are vulnerable to habitat fragmentation exacerbated by unfavourable land management, vagaries of the weather and the effects of climate change. Changes in agricultural practices have led to a reduction in suitable nesting sites and availability of food, particularly over the winter. Much of the chalk downland has been used for large scale arable production which has resulted in dramatic declines for species associated with less intensive farmland environments including arable weeds, farmland birds and mammals such as brown hare and harvest mouse.  Priorities relating to these species include:

• Promote the uptake of the Farmland Bird Package of options in environmental stewardship agreements to expand the core range of vulnerable farmland bird species.

• Increase the resilience of known populations of downland butterflies by improving habitat quality at existing key sites and looking for opportunities to link known colonies through arable reversion and creation of chalk grassland corridors and stepping stones.

• Co-ordinate survey and monitoring of key species.

Existing conservation projects and initiatives  

The South Wiltshire Farmland Bird Project –The South Wiltshire Farmland Birds Initiative is part of the wider South West Farmland Birds Initiative that works closely with farmers to stabilise and increase the numbers of farmland birds and rare arable plants. Through the use of Government grant schemes, such as Environmental Stewardship, land managers are encouraged to adopt measures that provide for farmland birds. This project has the potential to produce benefits that will be felt beyond this Area and it is important that efforts are made to find ways of connecting up those areas where active management for farmland birds and arable plant species is occurring.

Stepping Stones project – The project used the occurrence of six butterfly species found on calcareous grassland in this  Area - Dingy skipper, marsh fritillary, Adonis blue, chalk hill blue, Small blue and Duke of Burgundy -  to assess the ecological networks between areas of calcareous grassland. This project identified priority areas where appropriate habitat creation or restoration can enhance ecological connectivity  and offer significant biodiversity gains by buffering species from the impact of climate change and habitat degradation or loss. 

2. Rivers 

Chalk Rivers

The Hampshire Avon represents an internationally important chalk rivers system that supports rich and diverse communities of plants and animals, as well as associated habitats including lowland meadows and rush pastures. The unfavourable condition of the River Avon System SSSI, which includes the Wyle and the Nadder, is due to a number of factors including inappropriate water levels, invasive freshwater species, siltation, water abstraction levels, and water pollution resulting from both diffuse sources (e.g. agricultural runoff) and point discharges (e.g. some sewage treatment works). The Hampshire Avon has been identified as a Priority Catchment for work as part of the Government’s Catchment Sensitive Farming Scheme which aims to support action by farmers and land managers to tackle diffuse water pollution from agricultural sources. Priorities for chalk rivers include:

• Support catchment scale projects which contribute towards achieving Natura 2000 objectives for the River Avon SSSI and help meet the requirements of the EU Water Framework Directive to achieve ‘good ecological status’ of water bodies by 2015.

• Encourage the take up of capital grants available for the Nadder and Wylye catchments under the Catchment Sensitive Farming scheme to reduce agricultural and pesticide runoff, reduce soil erosion by livestock and vehicles, and halt river sedimentation from runoff

• The systematic monitoring and control of invasive plant and animal species along the length of the Salisbury Avon and its tributaries, coordinated with the provision of some replacement planting or specialist management to encourage a more appropriate flora. 

• Increase in the area of reedbeds, swamps and marsh habitats along the rivers to reduce run-off, increase the flood capacity of the river and provide habitat for riparian species. 

• Work with riparian landowners to implement sympathetic management, particularly restoration & enhancement works, to restore natural processes to the river and enhance resilience to climate change.

• Co-ordinated monitoring of rivers to identify presence of invasive plants and signs of pollution incidents affecting riverine fauna and flora

• Support management to benefit populations of native freshwater species including water voles, brown trout, brook lampreys, bullhead, white-clawed crayfish and riparian bird species.

Existing projects and initiatives  

There are a number of projects working to restore the River Avon to a naturally functioning and self sustaining river system that exhibits the full range of characteristic habitats that benefit the distinctive chalk stream flora and fauna. These include the Wessex Chalk Streams Project, the EA’s ‘Keeping Rivers Cool’ project and the ‘Source to Sea’ project (details of which are available in the Conservation Initiative section of the Area 9 profile). As part of the River Avon Restoration Plan a ‘Directory of Actions’ has been produced to provide a common direction for the many parties who wish to safeguard the River Avon. It provides specific information for each SSSI river reach as well as suggested restoration options. The current level of conservation work focussed on this chalk river system provides an important opportunity to make real and lasting improvements across the full extent of the Hampshire Avon system. It is important to support and, where possible, extend these efforts to maximise the benefits resulting from this body of work.

Catchment Sensitive Farming - The Hampshire Avon is designated as a Priority Catchment as part of the Catchment Sensitive Farming (CSF) scheme, with a CSF Capital Grant Scheme Target Area encompassing the Rivers Wylye, Nadder, East and West Avon. Capital grants are available in this target area for work to reduce agricultural and pesticide runoff in watercourses, limit physical damage to soil caused by livestock and vehicles, and halt sedimentation from runoff. Further buffering of these important chalk streams can be achieved by improving management of riparian habitat, including the control of non-native invasive plant species which should be coordinated with the provision of some replacement planting or specialist management to encourage a more appropriate flora.

3. Woodland

Lowland mixed deciduous woodland

Significant tracts of ancient and semi-natural woodland are located on the chalk ridges south of the Wyle and on the rounded chalk downs of the Cranborne chase. In 2009 the Cranborne Chase was identified as an Ancient Woodland Priority Area by the Forestry Commission. Priority Areas represent areas where landscape connectivity and permeability offer the best opportunity to link and extend ancient woodlands, either through new native woodland planting or through the management or creation of other semi-natural habitats. The agricultural and woodland heritage in the Cranborne Chase provides opportunities to implement management to improve biodiversity and at the same time harness the woodland resource for fuel and other renewable schemes. There is a need to extend and improve existing woodlands and link up those which are fragmented through restoration of hedgerows and planting of new trees. Priorities for this habitat include:

• Secure the favourable management of ancient woodland sites by engaging with landowners and promoting the use of agri-environment and Forestry Commission schemes to restore woodland structure and biodiversity.

• Buffer / extend ancient woodland sites with appropriate new woodland planting

• Improve connectivity between ancient woodland sites through hedgerow and woodland planting, and integrate them into the wider landscape

• Survey woodlands for the presence of priority woodland species including dormice, bats and breeding birds, ensuring that management reflects the needs of these species where present.

Existing projects and initiatives  

The Cranborne Chase Ancient Woodland Project aims to link up, extend and improve areas of ancient semi-natural woodland within the AONB via improved woodland management and the planting native woodland species in strategically important areas. This integrated project aims to deliver benefits for both the priority semi-natural woodlands and also for those using this important resource. Bats West Wiltshire is a key area for bats with a number of protected hibernation sites for several of the UK’s rarest species in the vicinity. Further work is also required to investigate the Area for significant bat roosts, of which many more are likely to be present than have currently been recorded. 

• Maintaining mature and veteran trees, particularly those known to be used for roosting

• Identifying and favourably managing the next generation of mature / veteran trees

• Managing existing hedgerows and woodland used for foraging and commuting routes

• Hedgerow planting and woodland creation to improve connectivity between key roosting / foraging sites

• Maintaining the important mosaic of woodland, grassland and open water habitats which help support such a rich diversity of bat species

• Identifying and mapping important roosting sites and foraging grounds for the rarest species

Existing conservation projects and initiatives  

Wiltshire Batscapes project – An area of opportunity has been identified under the proposed West Wiltshire Batscapes Project to take a strategic view of bat conservation across west Wiltshire and increase connectivity of woodland for bats commuting between Purbeck in Dorset and Woodchester in Gloucestershire. This project will employ agi-environment schemes to improve habitats for bats, particularly through new woodland / tree planting and maintaining grazed pastures

For the full West Wiltshire and Cranborne Chase Downs Landscape Biodiversity Area profile click here or view the entire Wiltshire & Swindon landscape-scale conservation framework here