Culm Measures

[1] They are so called because of the occasional presence in the Barnstaple–Hartland area of a soft, often lenticular, sooty coal,[2] which is known in Devon as culm.

[5][6] Culm grassland on the formation's slates and shales is composed of purple moor grass and rush pasture.

It is noted for a wide diversity of species, some extremely rare including the marsh fritillary butterfly.

The area is especially known for Culm grassland (nationally known as rhos pasture): species-rich pastures, typical of poorly drained acid soils, which support a suite of purple moor-grass and rush communities, forming a mosaic of vegetation communities with heathland, other species-rich grassland and wet woodland.

This is a habitat unlike any other in England, which supports distinctive and often attractive plant species, including heath spotted-orchid, southern marsh-orchid, bogbean, and saw-wort; a number of characteristic butterflies, including the marbled white, and marsh, heath, silver-washed and high brown fritillaries; and a number of typical bird species including grasshopper warbler and willow tit, as well as breeding Eurasian curlew and reed bunting, and overwintering snipe and woodcock.