Size: 25.94 hectares

% of total area of SSSIs: 6.38%

Designated features: heather, fulmar, guillemot, razorbill 

General Description

This small group of uninhabited islands including St Helen’s, Northwethel and Foreman’s Island are partially sheltered by Tresco and St Martin’s, but the rocky islet of Men-a-vaur to the north is fully exposed to the Atlantic. As result the latter has limited soil formation and has limited vegetation. Of note are small pockets of tree mallow and common scurvy-grass. However, the island supports eight species of breeding seabird including razorbill, guillemot and fulmar. The other islands have deeper soils which are dominated by bracken and bramble, which also supports a significant population of the balm-leaved figwort. The thin soils at the 40m summit of St Helen’s have led to the development of maritime heath, with its associated rich lichen flora, with flowering plants such as heather, bell heather and English stonecrop. The island's north-west slope is dominated by maritime grassland of red fescue, thrift and buck’s-horn plantain. The southern shore of St Helen’s is also important for species including tree mallow and wood small-reed, and it is one of the sites where the nationally rare shore dock has occurred. St Helen’s also holds good populations of greater and lesser black-backed gulls, along with a small colony of puffins and growing numbers of Manx shearwater.

Practical Management

Because of the importance of the island for breeding seabirds, the focus has been the removal of invading non-native karo (usually known as Pittosporum crassifolium) and tree bedstraw (another species more often known by its Scientific name of Coprosma repens) from the islands, particularly Northwethel and St Helen’s. These shrubs and trees provide look-out posts for carrion crows, which prey upon the young seabirds, as well as producing seeds which are an important source of winter food for brown rat. The Trust has also carried out annual bio-security to help control the number of rodents, which may otherwise take seabird eggs, along with managing vegetation around burrow entrances to ensure that seabirds have a tangle-free exit and entrance to their nest sites. We also clear areas within the scrub to provide space for groups of gulls to nest and lay their eggs, and as the young grow they are able to use the surrounding dense scrubby areas to hide from potential predators.

The island is also important for its archaeology, being one of the earliest Christian sites. It is a good example of an early medieval religious complex, lived in by Saint Lide. Not so romantic are the remnants of the isolation hospital used to quarantine victims of the plague. We play an active role in ensuring that these scheduled ancient monuments are kept clear of vegetation for the public to come and visit. As St Helen’s is open to the public there is a need to balance the needs of nature and for people to enjoy the landscape and the biodiversity around them. We work hard to provide well managed paths that permit the public to see the best of what the island has to offer, whilst ensuring that visits do not disturb the breeding seabirds.