Raised bogs are ombrogenous, i.e. are fed by rainwater, as they develop on deep peat which forms a barrier between the bog surface and groundwater sources. The habitat is relatively scarce in Wales and there are no ‘pristine’ examples, they have all been modified to a greater or lesser extent by peat cutting and drainage, with some examples also impacted by pipe-laying and burns. Two of the raised bogs in Wales are well known, however: Cors Caron for being the best example of a raised mire complex in the UK and Cors Fochno for being the largest single raised bog plateau in the UK. The reference state for raised bog vegetation and examples of modified states are given below.