WEG SSSI Fen Restoration

The Oxfordshire Fens Project has expanded to work on a further four SSSI fen sites, following the award of a Water Environment Grant in 2019. The project is working to restore these sites and improve fen habitat quality. 

Valley fens are amongst the richest of freshwater biodiversity hotspots when well-managed. However, such fens have been losing species due to lack of management, drying-out and loss of grazing, among other threats. The SSSI sites, all of which are currently partly classified as ‘Unfavourable’ in condition, have become dominated by tall vegetation, and, as natural succession has occurred, scrub and trees. Such vegetation shades and out-competes shorter plant species that are typical of alkaline fen short-sward.

A remnant Tussock Sedge (Carex paniculata) still hanging on at one of the SSSI fen sites. The tall sedge provides habitat for smaller wetland species.

Evidence of attempts to drain the land have also been found – for example, in the above photo, the area surrounding the artesian well was historically deepened to help dry out the fen. These activities have resulted in lowered water levels on the fens (drying-out), which has reduced habitat suitability for fen-specialist species. This is evidenced by the presence of Tussock Sedges (Carex paniculata) on dry ground within the fen area on one site – these long-lived plants typically only grow with their roots in water or very wet ground, and would have flourished in previous conditions before the fen became degraded. 

Clearance of vegetation, scrub and trees that have taken over the fen sites is currently underway.

The project is currently undertaking vegetation clearance and re-wetting works at the four fen sites, which will reduce shade and sward height, open up the fens and help to keep water on site, increasing habitat suitability for fen species. Material from the sites, such as the wood pictured above, will be used to create dams and bunds along watercourses to help re-wet the fen sites. 

Areas of internationally important alkaline fen habitat have become degraded due to a lack of management – here you can see the alder carr that has taken over.

However, a few nice wetland species are still present on the sites – we spotted Long-stalked Yellow-sedge (Carex lepidocarpa) and Common Frog (Rana temporaria) when visiting the sites in November 2019. Baseline plant and invertebrate surveys were undertaken at the four SSSIs before practical management work began, and these records will be used to assess progress as the short-sward alkaline fen habitat is slowly restored.