Unimproved Chalk Grassland
Unimproved calcareous grassland, of which chalk grassland forms a major component, is perhaps the single most important semi-natural habitat in the county. Indeed Wiltshire boasts around 55% of the entire British resource. It is also one of the richest with regard to the number of plants and animal species it supports including declining farmland bird species such as the Stone Curlew. Notable species include the Marsh Fritillary Butterfly and the Tuberous Thistle, which is almost restricted to a few sites in the county. Other distinctive species of the Wiltshire downlands include the Skylark, Brown Hare, Adonis Blue Butterfly and plants such as the Burnt-tip Orchid and Early Gentian.
In Wiltshire although most remaining sites are on steep un-ploughable downs, there are a number of extensive areas remaining on flat ground at Salisbury Plain and Porton Down where military activity and limited agricultural intensification have allowed such grasslands to thrive. Salisbury Plain alone has been described as the single largest area of unimproved chalk grassland west of the Urals. There are also a large number of chalk grasslands in Wiltshire which have been recognised as Wildlife Sites, road verges and the habitat may also be found in woodland glades. Chalk grassland is traditionally managed by grazing cattle or sheep or occasionally horses although some are cut for hay.
There are 62 Sites of Special Scientific Interest in Wiltshire (SSSIs) including Salisbury Plain and Porton Down. Pewsey Downs, Prescombe Down and Salisbury Plain (including Parsonage Down and Porton Down SSSI) are designated as Special Areas of Conservation (SAC) for habitats and species listed as of international importance in the European Habitats Directive.