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Cothill National Nature Reserve
Managed by:Natural England
OS grid reference:SU 4674 9953
Nearest postcode:OX13 6JW
Usual work:Fen Management, Scrub clearance

Cothill NNR is a species-rich lowland calcareous fen, and as such is a Special Area of Conservation (SAC). It has been a designated Site of Special Scientific Interest (SSSI) since 1950 and covers 43.55 hectares . Cothill Fen supports exceptional habitats of nationally rare calcareous fen and moss-rich, alongside wetland habitats that provide important habitat for a diversity of species including wetland invertebrates. There are also areas of woodland and herbaceous habitat at the site. Over 330 species of vascular flora and fauna have been recorded at the site, and the vegetation at Cothill Fen for the last ten millennia has been determined from examination of peat samples.

Geology

Cothill consists of small asymmetric valleys that provide the spring-fed waterlogged of the species-rich fen. The springs drain into the River Ock. The base of Corallian Calcareous stone is covered with rich peat and marl over parts of the site such as Morland’s Meadow, with calcareous humic gleys and free-draining brown earth providing diverse habitats elsewhere on the site.

Flora and Fauna

There are an abundance of flora and fauna at Cothill Fen. Of particular interest is the species-rich alkaline fen that provides habitat to grass-of-Parnassus, black bog-rush, semi-floating blunt-flowered rush, sundew, greater bladderwort, marsh orchid, parsley water dropwort, marsh pennywort, bottle sedge, and bogbean. Within the nationally important fen meadow purple moor-grass, common butterwort, meadow thistle, marsh helleborine, and tawny sedge can be found. A mosaic of mosses and liverworts are present here. A large number of species at the fen areas of site are rarely found outside East Anglia and parts of the West Country and Wales.

Within the drier parts of the site dyer’s greenweed, meadowsweet, tormenti, quaking-grass, yellow loosestrife and tor grass are present. A variety of deciduous woodland species and ground flora are found around the site, depending on the waterlevels of the underlying soil. This includes alder and sedges such as greater tussock sedge and thin-spiked wood sedge within the waterlogged areas. There are also coppiced alder and ash further away from the fen, alongside common spotted-orchid, dog's mercury, bluebell, yellow pimpernel, brooklime and scrub such as hawthorn, hazel and privet.

A large number of invertebrates have been recorded at Cothill Fen, including 12 species of flies that are rare within Britain such as the soldier flies Odontomyia angulata and Stratiomys chamaeleon. Rare species of snail and damselfields are also present at the site in addition to the scarlet tiger moth, great crested newt, common frog, common toad, grass snake and a variety of birds species that take advantage of the wide range of habitats present.

Conservation Management

Cothill Fen is managed by Natural England. Work done at the site that OCV have assisted with includes cutting of sedge and grass to encourage biodiversity within some of the denser areas of the site that can become dominated by a small number of sedge and grass species. Path maintenance is another important task at the site in order provide access to encourage visitors to stick to the paths rather than trample the delicate flora and fauna. This is of particular importance due to the high level of water at the site that can otherwise make use of the paths undesirable.

Location

From the Botley Interchange, (A34 / Botley Road junction), head west on the Botley Road (​A420). After passing Cumnor village, turn left onto Besselsleigh Road. Take the first right onto Lashford Lane, then turn right onto Church Lane. Turn right again onto Cothill Road.

The reserve is 500 metres from the village of Cothill and can be accessed via a public footpath from opposite the Merry Miller public house. There is a car park opposite the pub. The nearest car park to the reserve main entrance is at the entrance to the Dry Sandford Pit Nature Reserve on Honeybottom Lane.