Within a small area of north-eastern Anglesey, there is a series of remarkable fens and associated habitats of national importance, yet they are relatively little known except to specialists. The largest protected site is Cors Erddreiniog, which covers almost 300ha (of which about 80% is protected as an NNR); together with the nearby sites of Cors Goch (North Wales Wildlife Trust reserve), Cors Bodeilio (part NNR) and Cors y Fari SSSI, it forms an area of exceptional interest, with many scarce and rare species. Collectively, they are a Ramsar Site and proposed SAC.