UK: The Great Fen – last chance for endangered fen plants?


Alan Bowley from Natural England talks about this historic landscape and what the future looks like for its populations of special plants.

The fenlands of East Anglia occupy an area of some 3,800 square kilometres and for centuries remained a bog and marsh, impenetrable to all but the hardy ‘fen tygers’ (inhabitants of the fen). During the 17th century most of the area was drained for agriculture but some fragments remained - such as the great wetland around Whittlesey Mere at the very western edge of the fen basin.

Great Fen landscape

The great wilderness of woodland, scrub, and marsh was gradually destroyed by drainage for agriculture. Small sites were saved and the future for communities of wildlife and people in the Fen is now bright.

Until 1850 this area of some 4,000 hectares remained not only the mainstay of the local economy through fishing, wildfowling and reed harvesting, but  also a wildlife haven where plants like Sphagnum mosses, bog myrtle (Myrica gale), sundew (Drosera spp.) and bilberry (Vaccinium myrtilis) flourished. If the wilderness had survived it would surely now be a World Heritage Site. Sadly, this was not to be, for in 1851 a steam pump was used to drain the mere and over the next few decades the surrounding land was converted to arable land. Valuable though this was for food production the cost has been the wastage of 5 metres of peat soil and the loss of a unique wildlife resource.

During the 20th century two fragments of the wetland were rescued from wholesale drainage. Woodwalton Fen was purchased by the Hon Charles Rothschild and in 1919 became the first reserve of the Society for the Promotion of Nature Reserves (now Royal Society for the Wildlife Trusts) and a National Nature Reserve (NNR) in 1954. Holme Fen remained in private use as game cover until 1952 when it was purchased by the Nature Conservancy (now Natural England).

Both reserves suffered great damage from the effects of drainage – Woodwalton was farmed for some time and most of the upper peat layers were lost through digging for fuel. Holme Fen remains at the mercy of arterial agricultural drains and has developed into birch woodland, retaining just a tiny fragment of relict bog. But despite this damage an extraordinary number of species have survived.

picture of fen landscape

This land, looking over Woodwalton Fen, was arable as recently as 2004. Tussocks of soft rush (Juncus effusus) have responded aggressively to rising water levels and nutrient-rich soils. The western end of the drain has been blocked to isolate the land from the Internal Drainage board pumped system. This has been very successful: raising levels within the ‘new’ land has not affected surrounding arable land.

The fen woodrush (Luzula pallidula) was thought to be extinct in Britain until re-discovered at Holme Fen in 1948 by the famous botanist, Francis Rose. This delicate, honey-coloured little woodrush is demanding in its requirements and can be soon overwhelmed by competition from more aggressive species. Ground disturbance, however, can lead to spectacular results. Damage from forestry activities in the 1980s, for example, provided ideal conditions for thousands of woodrush plants to germinate over the next three or four years, but they gradually died out as the vegetation began to grow taller and the grass sward became thicker. This is a common pattern and one which cannot necessarily be replicated at will. Attempts at disturbance through ploughing and use of a ‘stone-burier’ attachment on a tractor have met with limited success. More natural processes, however, have been more productive. Birch woodland has grown up as the site has dried out due to agricultural drainage and as birch grows quite fast, structural change in the woodland structure is dynamic. Quite recently, the dense layer of bracken and bramble has been lost through a combination of development of a more closed tree canopy and the deprivations of Muntjac deer, and this has created suitable bare ground where small colonies of fen woodrush survive.

Fen violetAnother plant which has become equally endangered and presents similar management challenges is the fen violet (Viola persicifolia).

Fen violet is now found on only three sites in the Fens, but still has strongholds in mainland Europe and The Burren.

Once found in several locations across East Anglia and southern England it now occurs in just three sites - where populations are at extremely low ebb. Habitat loss due to the effects of drainage, ploughing and lack of management on many of its former sites have all had a major part to play in the dramatic decline of this beautiful plant. Although it grows widely in Europe in calcareous fen meadows and in Eire on The Burren, the fenland population struggles to survive.

Despite years of research and experimental management we can still not predict whether or not plants will germinate let alone flower and set seed. An example is the clearance of scrub in the 1970s using heavy machinery on an area of Woodwalton Fen where Viola had not been seen for many decades. Three years later, 8,000 plants were recorded, which has reduced to a few hundred within a decade. Today, there are often years when no plants appear at all, despite disturbance, water control and much praying! Hybridisation with Viola canina ssp. canina may also be a threat to the long-term future for this species.

Climbing corydalis

Climbing corydalis is a species making a recovery in the fens. Changes in woodland canopy cover has reduced the choking effects of bracken and bramble and allowed the plant to thrive. It now covers some 100 hectares at Holme Fen.

Climbing corydalis (Ceratocapnos claviculata) is not such a rare plant but one whose sole Huntingdonshire location is at Holme Fen. Unlike Woodwalton, the acid peat has survived here and forms a perfect habitat for this species. Changes in woodland structure have also suited it. Eighteen years ago, there was just one place where Corydalis grew along the edge of the woodland. Now it covers some 100 hectares where it has benefitted along with Narrow Buckler-fern (Dryopteris carthusiana) from reduction in the cover of bracken and bramble.

The future of plants like these hangs in the balance on these isolated sites where intensive ‘gardening’ is often necessary to sustain them. In addition, the gene pool is in becoming severely restricted, leaving fewer opportunities for selection of individuals able to adapt to climate change.

This tenuous future was a compelling reason behind the development of the vision for the ‘Great Fen’. Started in 2001, this project aims to re-connect Holme and Woodwalton and develop an enveloping landscape which will not only provide opportunities for plants and animals to migrate out of the isolated reserves, but also encourage people to experience an open space on the doorstep of the conurbations of Peterborough and Huntingdon. The Great Fen, together with the National Trust’s Wicken 100-Year Vision, heralds a new approach to conservation, where natural processes will be encouraged over large areas surrounding key wildlife sites.

Alan Bowley is the Natural England Senior Reserves Manager for the Fenland NNR and the Great Fen.

Visit the Great Fen Project website

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