Cors Fochno National Nature Reserve
This reserve, covering almost 7 square kilometres, includes the largest expanse of primary raised bog in Britain’s lowlands. Its Welsh name is Cors Fochno, recorded as Chors Vochno and Cors Mochno in early medieval times. Cors = bog. Mochno is the name of a person unknown to us today. To hear how to pronounce Cors Fochno, press play: Or, download mp3 (23KB)
The bog started forming 7,000 years ago when a spit of shingle gradually grew northwards from the shore, keeping the sea at bay. The area changed from brackish to freshwater swamp, then fenland. Alder, birch and pine woods appeared, then the area became a raised bog dominated by bog mosses and cotton grass.
After the climate turned wetter c.3,000 years ago, a type of sphagnum moss, Sphagnum imbricatum, dominated for c.2,500 years. Its well-preserved remains form much of the peat we see today. The peat also preserved stumps of trees from 5,000 years ago.
In 1813 an Act of Parliament authorised drainage and enclosure of Cors Fochno, which then covered c.24 square kilometres (6,000 acres). The surviving bog was designated a Site of Special Scientific Interest in 1954 but drainage reclamation continued until 1981, when the Nature Conservancy Council bought the area of today’s nature reserve. The bog is now part of Dyfi National Nature Reserve, managed by Natural Resources Wales. It can be viewed from the Wales Coast Path and nearby roads.
Cors Fochno is one of the last refuges of Sphagnum imbricatum in Britain. Other plants here include bog rosemary, bog myrtle, six species of carnivorous plants (which attract and trap insects for food), and lesser butterfly-orchid.
Rare invertebrates include the rosy marsh moth, large heath butterfly, hairy dragonfly and small red damselfly. The bog bush-cricket thrives here, as do adder, slow worm and palmate newt. Eel and fifteen-spined stickleback are the only fish that can survive in the acidic bog water.
Ditches in the bog are used by resident otters, and water voles have recently returned after being wiped out by non-native mink in the 1990’s. Birds seen here include redshank, snipe, water rail, teal, grasshopper warbler and reed bunting. Merlin, peregrine and hen harrier hunt here in winter, and red kites at all times of the year.
With thanks for place-name information to Prof Hywel Wyn Owen, of the Welsh Place-Name Society