Calcareous grassland is restricted to shallow soils derived from a variety of lime-rich bedrocks such as Carboniferous Limestone which was formed a staggering 350 million years ago. There is an estimated 10,000 ha of upland calcareous grassland in England, with particularly important areas for the habitat in the North Pennines (including the Yorkshire Dales National Park) and Cumbria.
These calcareous grasslands are broadly of two types. The first and least widespread are the blue moor-grass dominated upland grasslands. The more widespread type of calcareous grassland is more lowland in character and dominated by fescues and characterised by the presence of fine-leaved sedges. Richer grasslands may include a common milkwort and common rock-rose and rarely Frog Orchids and Field gentians.
Calcareous grasslands are of very high biodiversity importance in the Yorkshire Dales National Park. Both upland and lowland calcareous grasslands continue to be on the UK list of priority habitats for biodiversity action.