Through the Oxfordshire Fens Project, we're working with a community of Oxfordshire-based experts, volunteers, land managers and landowners to protect the county's internationally important alkaline fen habitat for the future.

Aerial view of alkaline fen with people raking and scything and electricity pylon.

Thanks largely to its geology, Oxfordshire has an internationally important concentration of alkaline fen habitat. This is a rare type of wetland fed by springs emerging from limestone. However, alkaline fens are often small and isolated wetlands, which – together with their wetness – makes them difficult to manage. Many have been neglected, and the short open vegetation has been lost through development of tall species-poor fen or scrub and woodland.

The Oxfordshire Fens Project aims to reverse this by restoring sites and their plant and animal populations. We’re also building and sharing evidence about the state of the county’s fens and how best to protect them.

What is alkaline fen?

Alkaline fen has a distinctive vegetation with a short, open structure made up of low-growing grasses, rushes and sedges, and a diversity of wetland wildflowers, growing over mats of colourful mosses. Alkaline fen supports supports some of the richest plant and animal assemblages in the country, including many rare and threatened species.

Alkaline fen in Oxfordshire is characterised by a suit of plants that are themselves locally uncommon, including Black Bog-rush (Schoenus nigricans), Blunt-flowered Rush (Juncus subnodulosus), small sedges such as Long-stalked Yellow-sedge (Carex lepidocarpa) and mosses such as Intermediate Hook-moss (Scorpidium cossonii). This vegetation supports a wealth of invertebrates. These include species of soldier-fly, horsefly and damselfly, while molluscs include the Desmoulin’s Whorl-snail (the infamous Newbury Bypass snail).

- Black Bog-rush growing in a moss hummock, Parsonage Moor. Phil Cutt

The state of Oxfordshire's alkaline fen

1 Sites

There are at least 64 alkaline fen sites in Oxfordshire, of which only 20% are legally protected.

2 Management

Most sites are not in conservation management, and 27% have succeeded to woodland, mostly during the last 50-100 years.

3 Loss of habitat

At least 14.5 ha of alkaline fen habitat is thought to have been destroyed.

At least 54.4 ha of alkaline fen habitat is thought to have been lost to trees and scrub. These are sometimes called ‘ghost fens’.

At least 13.2 ha of alkaline fen is overgrown with Common Reed (Phragmites australis) or other rank species-poor wetland vegetation.

4 Remaining habitat

10.71ha of existing high quality alkaline fen habitat remains in the county

8.9ha of alkaline fen habitat is being actively restored

5 Species declines

At protected sites, richness of alkaline fen vascular plant species has declined by around a third, and richness of the county’s uncommon species has declined by around half

Of the county’s uncommon alkaline fen vascular plants, 80% have been lost from at least 50% of their historic sites and nearly 30% have been lost from at least 75% of historic sites

How is Freshwater Habitats Trust restoring Oxfordshire's alkaline fens?

Thanks to a committed group of volunteers, we’re restoring some of Oxfordshire’s alkaline fens.

We run regular working parties at Hinksey Heights fen and Coleshill fen. Here, our volunteers get involved with clearing reed and other vegetation, to allow fen species to return. Activities also include raking, and spreading Marsh Lousewort seed.

If you would like to join us as a volunteer on the Oxfordshire Fens Project, please contact our fen conservation officer Paola Perez (

Woman scything in a field

- Paola Perez, Freshwater Habitats Trust

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