How Wildlife Trust extended the Fleam Dyke habitat – and is reprofiling woodland rides in Cambridgeshire

Fleam Dyke, the huge earthwork monument running between Fulbourn and Balsham, is an impressive presence in the landscape.

At the end of last year, the Wildlife Trust in Cambridgeshire took the opportunity to bring a significant length of the dyke into ownership, extending the habitat, and creating a larger, better connected nature reserve, linking to and incorporating Fulbourn Fen nature reserve, thanks to a highly successful appeal.

The trust is very grateful for the enthusiastic support of the local community, as well as national support for and interest in this archaeologically significant site.

The section between Fulbourn Fen and Mutlow Hill, together with a further 7.6 hectares of arable land adjacent to the earthwork, will now see the creation of new chalk grassland habitat for the benefit of all chalk flora and fauna, enabling a more sustainable management of Fleam Dyke.

Land management will focus initially on the remnant chalk area on Mutlow Hill, then along the footpath and upper slopes of Fleam Dyke, with restoration of areas of scrub on the middle and lower slopes taking place in the future.

The additional arable land will be sown with a chalk grassland wildflower mix in 2024, and, in the fullness of time, Fulbourn Fen and Fleam Dyke will become a single site, managed through conservation grazing with a mixture of cattle and sheep.

Grassland improvements will allow the rich range of wildflowers to flourish - early spring sees violets and cowslips, followed by low growing plants typical of chalk grassland - common rock rose, horseshoe vetch, wild thyme, milkwort and eyebright.

By summer lady’s bedstraw forms a backdrop to the mauve, purple and blue of knapweeds, small scabious, field scabious, clustered bellflowers and harebells together with salad burnet, dropwort, restharrow and ploughman’s-spikenard. Patches of starry white squinancywort, bright pink sainfoin and an occasional pyramidal orchid may also be seen.

Constructed sometime between the 4th and 5th centuries by Anglo Saxon settlers, the Dyke is three miles long and seven metres high from ditch to bank, forming a barrier across the open chalkland ridge.

Most probably designed for defensive purposes, it later served as a boundary between the Flendish and Staine Hundreds (most counties in England were divided into hundreds - larger than villages but smaller than shires).

The Flendish Hundred was mentioned in the Domesday Book and included Fulbourn, Fen Ditton and Horningsea, while the Staine Hundred included Great and Little Wilbraham, Stow, Quy and Bottisham. Hundreds were later abandoned as administrative divisions in the 19th century.

Mutlow Hill is a Bronze Age burial barrow dated to 2000BC which was excavated in the 1850s and found to contain eight funeral urns holding cremated remains and some beads originating from the Mediterranean.

Between 1912 and 1915, Fleam Dyke was one of 286 sites selected by Charles Rothschild, founder of the Wildlife Trusts movement, as a wildlife site worthy of preservation - the entire site is now a Scheduled Monument and a Site of Special Scientific Interest.

Reprofiling woodland rides

The trust's ancient woodlands in Cambridgeshire annually become very wet and muddy in winter, with the central rides becoming eroded in the middle, so retaining water instead of it draining away, with many years of access heavily compacting the soil.

In recent years the trust's reserves team have experimented with a trial re-profiling of a 200m stretch on the main ride at Waresley and Gransden Woods.

Sian Williams, senior monitoring and research officer, explains: “While the work looked drastic at the time, involving moving soil with a digger and loss of ride vegetation, the re-profiled section is now higher in the middle, with new ditches cleared to either side helping water to drain away. Impacts were monitored by recording and mapping plant species before and after - plants recolonised very quickly and by June 2022, the ride had mostly greened up.

“By 2023, the vegetation was long enough to need mowing, full of plants including lots of flowering nectar sources. This is good news for other potential reprofiling projects, and shows that it can be done without a major impact on the flora.”

The reprofiled section was closed to visitors until August 2023 to help the vegetation to establish - not everyone respected the signs and there was still some regular foot traffic along the ride; the area will remain monitored for the next two years to gauge impacts.

Some woodlands, including Waresley and Gransden, are currently closed due to excess waterlogging: the trust never likes to close woods but prolonged milder and wetter winters means this is increasingly becoming more of an annual necessity. Please check before visiting at www.wildlifebcn.org/explore/reserve-updates

Visit www.wildlifebcn.org/blog/matt-hamilton/why-are-woodland-closures-needed for more on woodland closures.