The highs and lows of drought at Silent Pool

Despite the heavy rain of the past fortnight, the persistent drought is having a massive effect on Silent Pool, a Site of Nature Conservation Importance (SNCI) which lies within the Surrey Hills Area of Outstanding Natural Beauty (AONB) near Shere, reports Surrey Wildlife Trust (SWT).

The Trust, which manages an Access Agreement between Surrey County Council and the Albury Estate, is one year into a 3 year Biffaward funded project to improve the habitat value of the reserve’s woodland and ponds, as well as the paths and revetments around Silent Pool. 

Although low water levels seem to be causing problems for wildlife in the short term - the upper pond is only 6 inches deep (instead of the usual 9ft) and the reserve’s moorhen population is now confined to lower ‘Sherbourne Pond’ (which is 2ft lower than normal) -  they are also proving strangely beneficial.

Over £6,000 of Biffaward’s £49,960 grant is allocated to control of the highly invasive, non-native aquatic plant Australian swamp stonecrop (also known as New Zealand pigmyweed), and the drop in water level has allowed SWT’s contractor, Amenity Water Management, to spray herbicide directly onto the plants (saving the effort and cost needed to pump the pond dry in order to allow the chemical to take effect).

The reserve’s two ponds were badly infested with this plant (which was brought to Britain for aquaria and probably introduced to Silent Pool on a bird’s foot - picked up from another water body - or dumped in the pond along with unwanted pet fish) which was seriously threatening native species. It formed dense mats of choking vegetation which out-competed and eliminated other aquatic plants, degrading the habitat of invertebrates and amphibians and severely reducing biodiversity.  So, the weed will get three herbicide treatments per year, every year, after which time pre-planted hessian rolls will be staked down at the ponds’ margins to ensure native plants get a foothold again.

Visitors will benefit from a new viewing platform, causeway and improved culvert, built with chestnut timber from SWT’s Chinthurst Hill Local Nature Reserve.  Volunteers have coppiced hazel trees and cleared overhanging branches from around the pond margins to allow light in, as well as reinforcing revetments to hold back slumping soil around Silent Pool’s walkways.

Leo Jennings, SWT ranger, said: “Even with the recent rain, it may well be autumn before the chalk aquifer is re-charged and the Silent Pool spring starts to flow again. Come and join a guided walk, at 2pm on Saturday 12th May, to find out more about the management and history of this special reserve.”

To get involved as a volunteer, please contact anna.fosbery@surreywt.org.uk. 
For more information about protecting the countryside from invasive species, visit www.direct.gov.uk/beplantwise and http://www.ceh.ac.uk/sci_programmes/documents/AustralianSwampStonecrop.pdf