A Biffaward grant enabled the National Trust to embark upon an ambitious project in 2006, at the Calke Abbey National Nature Reserve (NNR). The biodiversity development project addressed the need to restore ecology in the reserves' ponds. This was especially important for the globally threatened white-clawed crayfish, a rare UK BAP priority species, which was surviving in less than ideal habitat conditions in at least one of three ponds in Calke Abbey NNR.

Background:

A series of ponds were created in the 18th and 19th Century at the National Trust's Calke Abbey Park by damming the Jubilee Brook. With time, the ponds developed into valuable wildlife habitats and are now integral to the Calke Abbey NNR. More recently, a combination of suspended sediments and pollutants from the farmed catchments plus re-suspension of sediments by stocked carp has resulted in a deterioration of water quality and a decline in ecological value of the ponds. The weirs and culverts that were created and divide the ponds have likewise deteriorated with time and require a programme of repairs in order to conserve both them and the ponds.

In 2005, the Trust commissioned an ecological survey of the ponds. The survey revealed the presence of white-clawed crayfish thus reconfirming the presence of this species after an "absence" of some 20 years or more. Poor amphibian populations were attributed to the presence of carp. Aquatic macrophytes were likewise sparse due in part to the impact of fish but also the blocking of light by the perpetually re-suspended sediments. Action was needed.

This project aims to remove threats and create a long-lasting, sustainable solution to enable Calke's UK BAP priority species to thrive. The main elements to the projects are:

• Structural repairs to weirs
• Installation of rip-rap refuges for crayfish
• Crayfish monitoring and biometrics
• Carp removal from upper pond (Betty's)
• Creation of a "buffer" wetland upstream of the ponds
• Partial dredging of Betty's Pond
• Installation in the buffer wetland area of learning facilities and opportunities

The new wetland will function as a silt trap and as a water "polisher" but also provide new habitat for crayfish and other wetland wildlife.

The ultimate aim of the project is to restore the ecology of the ponds, to produce clear water with abundant aquatic plants and invertebrates, a thriving white-clawed crayfish population and to return the amphibian population to its former 50,000 plus toads! Monitoring the ecological recovery is an important aspect of the project and both professional expertise and volunteer assistance will be utilised in order to do so.

Repairs to the weirs commenced in May 2007 and the latest update from the project is that construction is now complete. Survey work on white-clawed crayfish has been recently carried out and shown a population increase of 2,000 per cent from a baseline of two specimens. This is fantastic news and Biffaward wish this project every further success.

For more information on Calke Abbey NNR, visit www.nationaltrust.org.uk