rcscorer's picture

Brecon Beacons

Observed: 8th July 2009 By: rcscorerrcscorer’s reputation in Plantsrcscorer’s reputation in Plantsrcscorer’s reputation in Plants

I am curious to know what these raised islands are called and what causes them. The second picture shows a similar feature near the summit of Plynlimon in mid-Wales.

    Likely ID
    Human (Homo Erectus)
    Confidence: It's likely to be this, but I can't be certain.
Species interactions

No interactions present.


chrisbrooks's picture


I believe that the raised areas are the original ground level and the the lower areas are where the soil has been eroded away by the weather. This is a serious problem in the Brecon Beacons and steps are being taken to restore the vegetation to prevent further erosion taking place.

If you go to the summit of Waun Fach in the Black Mountains you will see that the landscape is just like this or worse. Waun Fach is just an example but one where the issue can be clearly seen.

Beagle's picture


It is difficult to be specific but generally speaking Plynlimon and this area of Wales were subject to glaciation and drainage erosion which resulted in flooding and loss of biodiversity. Plynlimon itself is the third highest mountain in Wales and a huge watershed for three rivers; Severn, Wye and Rheidol. My dad, from the Black Mountains, used to call these mounds 'peat-hags'. Regards


RHoman's picture

Upland peat

The causes of this type of landscape are complex and could involve past management such as burning or grazing. Upland drainage is certainly a significant factor. Peat holds huge quantities of water. If the land is drained, in order to increase its agricultural potential, then shrinkage occurs. Dry peat is more prone to erosion compared to wet peat with a vegetation cover. Exploiting the peat for fuel in such a location is unlikely - imagine the task of moving it to "nearby" dwellings. The sponge effect of peat plays an important role in controlling the rate of flow in the streams coming off such areas - less peat = more rapid flow = increased risk of flooding lower down the water courses. Peat is also an important carbon sink - hence the emphasis on restoring this type of landscape with re-seeding and re-wetting.

Robert Homan