Calcareous Grassland

Lowland calcareous grassland has suffered a sharp decline in extent in the UK over the last 50 years. There are no comprehensive figures, but a sample of chalk sites in England surveyed between 1966 and 1980 showed a 20% loss in that period and an assessment of chalk grassland in Dorset found that over 50% had been lost between the mid-1950s and the early 1990s (UK BAP Lowland Calcareous Grassland HAP).

 Current estimates put the amount of lowland calcareous grassland remaining in the United Kingdom at around 33,000 to 41,000 ha. The bulk of the resource is found on chalk (25,000 to 32,000 ha), with major concentrations in Wiltshire, Dorset and the South Downs.

Lowland Calcareous Grassland: definition

Lowland calcareous grasslands have developed on shallow lime-rich soils, generally overlying limestone rocks, including chalk. The thin, well-drained nutrient-poor soils support a characteristic variety of herbs and grasses. These grasslands are now largely restricted to distinct topographic features such as escarpments, dry valley slopes or ancient earthworks, strongly influenced by the underlying limestone geology.

There are a few remaining large areas on flat ground, and some small remnants occur along road verges and in woodland glades. Calcareous grasslands are typically managed as components of pastoral or mixed farming systems, supporting sheep, cattle or occasionally horses. A few are cut for hay. The definition of calcareous grasslands covers a range of plant communities in which lime-loving plants are characteristic. In the UK BAP HAP for Lowland Calcareous Grassland, lowland types are defined as the first nine calcareous grassland National Vegetation Classification communities, CG1 to CG9.

The extent of calcareous grassland

Wiltshire has between 18,000 and 24,000ha of calcareous grassland, which equates to approximately 50% of the total UK calcareous grassland resource. The Salisbury Plain Training Area (SPTA) has approximately 12,000ha of chalk grassland. This alone, represents 41% of the chalk grassland in North West Europe. Despite the large extent of calcareous grassland remaining in Wiltshire, there have still been significant losses historically, mainly due to ploughing and agricultural intensification. Unusually for this habitat nationally, there are a number of extensive areas of calcareous grassland remaining on flat ground in Wiltshire, as on Salisbury Plain and at Porton Down, where the grasslands have survived due to military occupation which has limited agricultural intensification.

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