On how calcium carbonate at historic sites helps wildlife thrive

A magical visit to Warham Camp last month reminded me of the significance historic sites can have in providing micro-habitats for flora and fauna.

During August I carried out my regular site visits to the Trust properties in the west of the county. While I was there I took the opportunity to eat my packed lunch at Warham Camp, the best preserved Iron Age fort in East Anglia. Although the Trust doesn’t manage this site we assisted the Holkham Estate in producing a new interpretation board which was installed last year.

The two massive earth banks and ditches were built out of hard chalk to enclose a circular area of around 1.5 hectares. As a consequence, the grassland here supports chalk-loving flora not often found in Norfolk.  During my visit the banks of the fort were alive with clouds of Chalk Hill Blue butterflies attracted by the flowers – a magical experience.

At Caistor Roman Town the south and west banks are designated as a county wildlife site because of the chalk-loving plants which appreciate the conditions created by the Roman lime mortar - chalk and lime are both forms of calcium carbonate. At Binham Priory the precinct wall is designated as a Roadside Nature Reserve because it supports a rare colony of wall bedstraw in the lime mortar. And an ecological survey of the walls at Burnham Norton Friary gatehouse, carried out this summer, has identified small colonies of two rare species  of plant for the county – the flattened meadow-grass Poa compressa and a member of the bryophytes division (mosses and liverworts)Porella platyphylla. The survey was commissioned as part of the preparation for carrying out repairs to the wall, and these two colonies will now be protected during the works.

The survey also highlighted that the habitat is particularly suitable for reptiles which may bask around the south and south-west facing perimeter walls, either at the base of the wall or on top of the low sections, especially in spring and autumn when they are emerging from or going into hibernation sites. Grass snakes are likely to be present and possibly common lizards and slow worms.

This knowledge enables us to plan repairs and maintenance for the conservation of the site while protecting and supporting biodiversity – two key aims of the Trust.

Plants thriving at Caistor Roman Town

News in brief

  • Saturday 12th and Sunday 13th September: Heritage Open Days at St Benet's Abbey guided tours on the hour from 11am until 3pm on both Saturday and Sunday. Also two guided walks on Sunday from Ludham Bridge, one at 10am to link up with the 11am tour and one at 2pm to link up with the 3pm tour. There will also be a stall with information about The Friends of St Benet's Abbey and guide books on sale. For more information email tfosba@gmail.com
  • Sunday 27th September: Tours of Pykerell’s House Norwich -  a few spaces left on the afternoon guided tours of this remarkable fifteenth-century hall house acquired by the Trust in 1928. For more information please contact Maureen Kimbley: maureenkimbley@norfarchtrust.org.uk      Tel: 01263 587705
  • Volunteering: if you visit one of our sites frequently, perhaps for exercise, to walk the dog, or to watch wildlife, you could really help the Trust by letting me know if you spot anything that needs attention. For example, volunteer wardens at Caistor have recently alerted me to the presence of Japanese Balsam on the river bank, and to the fact that a visitor had built a dam across the river. I visit all our sites regularly but it’s always helpful to know that other people are keeping an eye on them in the meantime. If you would like to help with this please get in touch: carolinedavison@norfarchtrust.org.uk 01603 462987