Buckinghamshire & Milton Keynes Biodiversity Action Plan Lowland Calcareous Grassland Habitat Action Plan

Lowland Calcareous Grassland

Key associated species

Chalk Carpet Moth Chalkhill Blue Chiltern Gentian Duke of Burgundy Early Gentian Glow Worm Green Hairstreak Hornet Robber Fly Horseshoe Vetch Juniper Linnet Meadow Clary Pasque Flower Roman Snail Silver-spotted Skipper Snail Abida secale Stone Curlew Striped Lychnis Moth Yellow Meadow Ant

This habitat includes all semi-improved grassland and unimproved grassland occurring on shallow lime-rich soils normally underlain by chalk or limestone rocks. Calcareous grassland is associated with distinct topographic features such as escarpments or dry valley slopes and ancient earth works. Lowland calcareous grassland supports a very rich flora with many nationally rare and scarce species together with a diverse invertebrate fauna such as Chalkhill Blue and Duke of Burgundy butterflies. Scrub, such as Juniper and Box, is associated with calcareous grassland and contributes to local biodiversity.

1 Current status in the UK

Biological status

1.1 Calcareous grassland is a rich grassland type in terms of the diversity of plant and invertebrate species supported. Many species are confined to calcareous grassland in the UK, including those that are on the northern edge of their European range.

1.2 Lowland calcareous grasslands are defined by the UK Biodiversity Group as the first nine communities in the National Vegetation Classification CG grouping. These communities are largely restricted to the warmer and drier climate of southern and eastern areas of the UK.

1.3 The amount of calcareous grassland has undergone a significant decline over the last 50 years. Although there are no detailed figures available for the UK as a whole, local statistics demonstrate the overall decline eg 50% lost in Dorset between the mid-1950s and the early 1990s, 25% lost in Sussex between 1966 and 1980. No figures are available for Buckinghamshire.

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1.4 Current estimates for lowland calcareous grassland in the UK are between 33,000 and 41,000 ha with less than 1,000 ha in Wales and none in Scotland. The majority of this is associated with chalk (25,000 to 32,000 ha) with the key concentrations in Wiltshire, Dorset and the South Downs.

2 Current status in Buckinghamshire

Cover and distribution

2.1 Buckinghamshire has over 350 ha of calcareous grassland, the majority of which occurs in the Chilterns though it is also found on the Cornbrash and Oolitic limestone in the north of the County. Approximately 100 ha of Local Wildlife Sites are currently attributable to Lowland Calcareous Grassland.

2.2 The distribution of calcareous grassland is linked to the geology of the County, developing on shallow, lime-rich, nutrient-poor soils derived from chalk and limestone rocks. In Buckingham-shire, the largest areas occur along the Chilterns escarpment such as the Ivinghoe Hills, Coombe Hill, Kimble Warrens, Grangelands and Pulpit Hill. As a result of scrub encroachment and agricultural improvement a large proportion of the remaining calcareous grassland occurs on inaccessible land on steep scarp slopes, in dry valleys, on railway cuttings and on old earth workings such as Aston Clinton Ragpits. These areas often occur within a larger mosaic of scrub, woodland and hedgerows. Alternatively, it may be isolated in large tracts of intensively managed farmland.

2.3 This habitat supports indigenous populations of grasses and wildflowers and includes some of the most diverse plant communities in Britain. The resource is of international importance. National Vegetation Classification (NVC) CG 2,3 and six communities are recorded on calcareous grassland.

2.4 A special feature of the calcareous grassland in the Chilterns is that it is frequently found in an intimate mosaic of large blocks of woodland and valuable hedgerows. In some areas such as at Coombe Hill SSSI the lower slopes of calcareous grassland link to the plateau which is capped with a shallow layer of clay-with-flints. Where the plateau remains free from woodland cover and agricultural improvement, this may give rise to acidic grassland and even chalk heath.

2.5.1 The occurrence of calcareous grassland as a mosaic with scrub and woodland results in a diversity of habitats, which combined, are of high conservation value. Indeed, scrub often acts as a key feature which links grassland and wooded areas. Scrub communities also have

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inherent ecological value, particularly for invertebrates, for example, the Duke of Burgundy butterfly. This means that any proposals for scrub clearance should be thought through carefully and an assessment made of its existing value. Clearly, a balance needs to be determined as excessive scrub encroachment and the dominance of vigorous grass species can significantly reduce the conservation value of a site.

Trends 2.6 A significant decline in the extent and quality of calcareous grassland has occurred this century, principally as a result of scrub encroachment and agricultural development. Conversion of large areas of pasture to arable land has been followed by the loss of remaining grassland to scrub and secondary woodland, usually small unmanageable areas along the scarp or valley sides. The latter was exacerbated by the crash in rabbit populations following the introduction of myxomatosis in the 1950s, although rabbit populations have subsequently recovered.

3 Current factors affecting the habitat

Agricultural intensification 3.1 Agricultural improvement through fertiliser and herbicide applications, ploughing and seeding has been driven by a combination of technological improvements but latterly by the Common Agricultural Policy and its associated subsidies.

Lack of management 3.2 Undergrazing, or cessation of management results in a rank sward and eventually scrub and secondary woodland. Fluctuating rabbit populations have an important role in grazing intensity.

Built development 3.3 Industrial and urban development leads to losses. This includes the infilling of abandoned chalk and limestone quarries where calcareous grassland has become established after cessation of work.

Recreation use/pressures

3.4 Conflicting land uses such as pony paddocks, tree planting and golf courses can lead to a deterioration in habitat. Lack of public understanding over conservation management, especially removal of scrub should be addressed in order to increase awareness of the need for management. High levels of public access and recreation on certain sites can lead to erosion.

Habitat isolation 3.5 Habitat fragmentation of calcareous grassland areas results in poor recolonisation and loss of species from sites. Site size is linked to the

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economic viability of management. This has important implications for sustainable management.

4 Current action

Legal status 4.1 Eighteen of Buckinghamshire’s key calcareous grasslands are protected as SSSIs. In addition some sites have been identified as Wildlife Sites which, although non-statutory, confers some protection from development and encourages positive management.

Management, research and guidance 4.2 Traditionally these areas were grazed by sheep and occasionally cattle, producing a close-cropped sward.

4.3 The restoration of grazing on abandoned grassland and scrub management (rather than eradication) are priorities for the future management of calcareous grassland.

4.4 The Chilterns Chalk Managers Group provides a network for exchange of knowledge and resources throughout the Natural Area.

5 Objectives

5.1 It is important that Habitat Action Plan objectives and actions are considered in conjunction with those in Generic Issues (see Generic Issues). All Generic objectives and actions apply to each individual Habitat Action Plan.

5.2.1 The Calcareous Grassland HAP will contribute to the following UK BAP Targets

T1 Maintain the current extent of Lowland Calcareous Grassland in the UK. (Target represents no loss of BAP habitat).

T2 Maintain at least the current condition of Lowland Calcareous Grassland

T3 Achieve favourable or recovering condition for 30,421ha of Lowland Calcareous Grassland by 2010

T4 Restore 399ha of Lowland Calcareous Grassland from semi- improved or neglected grassland, which no longer meets the priority habitat definition by 2010

T5 Re-establish 8,424ha of grassland of wildlife value from arable or improved grassland by 2010.

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T6 6,320 ha (75%) of re-established area to be adjacent to existing Lowland Calcareous Grassland or other semi- natural habitat by 2010. (Refer to T5)

T7 4,200 ha (50%) of re-established area to contribute to resultant habitat patches of 2 ha or more of Lowland Calcareous Grassland by 2010. (Refer to T5)

6. Biodiversity Opportunity Areas

Calcareous Grassland may be a priority habitat in the following Biodiversity Opportunity Areas

• Ashridge & Ivinghoe • Central Chilterns Chalk Rivers • Chess Valley • Chiltern Escarpment • Gomm Valley • Hambleden and Wormsley Valleys • Medmenham • Ouse Valley • Radnage Valley • South Bucks Heaths & Parklands • South Western Commons • Upper Hughenden Valley • Wendover Woods

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National Target Code Target Action Start End Action location Lead Other Orgs Target Baseline total T1 - Maintain the current extent of CG1 Maintain current extent 2007 2010 X ha X ha Lowland Calcareous Grassland in of lowland calcareous the UK. (Target represents no grassland in Bucks loss of BAP habitat). T2 - Maintain at least the current condition of Lowland Calcareous Grassland. CG1/1 Monitor and maintain current extent of 2007 2010 Aylesbury Vale TBA AVDC 30 ha 30ha lowland calcareous grassland in BBOWT CCB Aylesbury Vale FWAG NE BMKBP NT CG1/2 Monitor and maintain current extent of 2007 2010 Chiltern TBA CDC BBOWT 1 ha 1 ha lowland calcareous grassland in CCB FWAG Chiltern NE BMKBP CG1/3 Monitor and maintain current extent of 2007 2010 Milton Keynes TBA MKC MKPT 3 ha 3 ha lowland calcareous grassland in Milton BMKBP Keynes CG1/4 Monitor and maintain current extent of 2007 2010 Wycombe TBA WDC BBOWT 172 ha 172 ha lowland calcareous grassland in CCB FWAG Wycombe NE BMKBP NT T3 - Achieve favourable or CG2 Achieve favourable or recovering condition for 30,421ha recovering condition of of Lowland Calcareous Grassland calcareous grassland by 2010. CG2/1 Achieve favourable or recovering 2007 2010 Aylesbury Vale NE AVDC 27 ha condition of calcareous grassland in BBOWT CCB SSSIs in Aylesbury Vale FWAG NT CG2/2 Achieve favourable or recovering 2007 2010 Wycombe NE WDC BBOWT 97 ha condition of calcareous grassland in CCB FWAG SSSIs in Wycombe NT CG2/3 Achieve favourable or recovering 2007 2010 Aylesbury Vale TBA AVDC X ha X ha condition of calcareous grassland in BBOWT CCB non-statutory sites in Aylesbury Vale FWAG NE NT CG2/4 Achieve favourable or recovering 2007 2010 Chiltern TBA CDC BBOWT X ha X ha condition of calcareous grassland in CCB FWAG non-statutory sites in Chiltern NE CG2/5 Achieve favourable or recovering MKC NMKPT X ha X ha condition of calcareous grassland in NE non-statutory sites in Milton Keynes

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CG2/6 Achieve favourable or recovering 2007 2010 Wycombe TBA WDC BBOWT X ha X ha condition of calcareous grassland in CCB FWAG non-statutory sites in Wycombe NE NT T4 – Restore 399ha of Lowland CG3 Create chalk grassland X ha Calcareous Grassland from semi- of wildlife value, with aim improved or neglected grassland, to link small, vulnerable which no longer meets the priority and isolated chalk habitat definition by 2010. grassland sites CG3/1 Create chalk grassland of wildlife value, 2007 2010 Aylesbury Vale TBA AVDC X ha 0 with aim to link small, vulnerable and BBOWT CCB isolated chalk grassland sites in FWAG NE NT Aylesbury Vale CG3/2 Create chalk grassland of wildlife value, 2007 2010 Chiltern TBA CDC BBOWT X ha 0 with aim to link small, vulnerable and CCB FWAG isolated chalk grassland sites in NE Chiltern CG3/3 Create chalk grassland of wildlife value, TBA MKC MKPT X ha X ha with aim to link small, vulnerable and NE isolated chalk grassland sites in Milton Keynes CG3/4 Create chalk grassland of wildlife value, 2007 2010 Wycombe TBA WDC BBOWT X ha 0 with aim to link small, vulnerable and CCB FWAG isolated chalk grassland sites in NE NT Wycombe T5 – Re-establish 8,424ha of CG4 Re-establish chalk 2007 2010 X ha grassland of wildlife value from grassland of wildlife arable or improved grassland by value from arable or 2010. improved grassland T6 – xxx ha (75%) of re- established area to be adjacent to existing Lowland Calcareous Grassland or other semi-natural habitat by 2010. T7 – xxx ha (50%) of re- established area to contribute to resultant habitat patches of 2 ha or more of Lowland Calcareous Grassland by 2010. CG4/1 Re-establish chalk grassland of wildlife 2007 2010 Aylesbury Vale TBA AVDC X ha 0 value from arable or improved BBOWT CCB grassland in Aylesbury Vale FWAG NE NT CG4/2 Re-establish chalk grassland of wildlife 2007 2010 Chiltern TBA CDC BBOWT X ha 0 value from arable or improved CCB FWAG grassland in Chiltern NE

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CG4/3 Re-establish chalk grassland of wildlife TBA MKC MKPT X ha X ha value from arable or improved NE grassland in Milton Keynes CG4/4 Re-establish chalk grassland of wildlife 2007 2010 Wycombe TBA WDC BBOWT X ha 0 value from arable or improved CCB FWAG grassland in Wycombe NE NT CG5 Engage at least one 2007 2010 Bucks & MK 2 private business and busine one community group in sses / calcareous grassland organi restoration/creation or sation monitoring project s CG5/1 Engage at least one private business 2007 2010 Bucks & MK BMKB AVDC 2 and one community group in P BMKBP busine calcareous grassland BBOWT CCB sses / restoration/creation or monitoring MKC CDC organi project WDC sation s

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