Ecological Assessment of the Folk Festival stage over Cherry Hinton Hall lake – Report to the Friends of Cherry Hinton Hall
Guy Belcher, Nature Conservation Officer, Cambridge City Council
Prompted by concerns raised by members of the Friends of Cherry Hinton Hall, I was asked by Anthony French to assess the potential ecological impact of the proposed structure over the weir. I requested details of the proposed structure, including lighting, services, set up and operation programme. From my knowledge of the site I was able to identify the following ecological risks (please see below) that were fed back to the event organisers to establish if the risks could be suitably reduced or mitigated.
In response, the Folk Festival team employed Jade Cawthray to oversee the mitigation. She holds an environmental degree, lives locally to the site and has experience of monitoring bats through work with the Local Wildlife Trust. We met on site to discuss the issues and I was confident she had the appropriate skills to undertake this work.
1) Disturbance to Wildfowl
I viewed this as a minimal risk as many of the birds present are semi-domesticated and used to year-round presence of people and dogs. A search for any active nests in the vicinity was made and none located. A moorhen brood had recently fledged, below a tree proposed to be illuminated, but the young had left the nest. It was agreed that suitable feed would be used to encourage the main feeding flock to move away from the location of the structure during the stage construction and the event.
2) Pollution of the watercourse
Initially the proposals suggested the platform staging would be painted in situ. This posed considerable risk of chemicals entering the chalk stream. It was agreed that no such activity would take place over the waterway.
3) Disturbance to foraging bats
In my view this represented the most significant ecological concern as previous bat monitoring has revealed good numbers of three species of bat using the water body to hunt insects. The brick bridge was also surveyed to ensure no bats were roosting within the structure.
I carried out a survey (using bat detectors) of bat activity with Jade on the evening of the 17th July 2012. This revealed that post 10 pm good numbers of Pipistrelle bats (both Common and Soprano) were feeding over the lake and particularly along the adjoining woodland edge. A few individuals were also hunting along the brook. One interesting point was that three individual Pipestrelles concentrated their foraging over the small wildflower and thistle patch by the lakeside play area. This shows the value of such areas for producing insect prey for bats and birds. Smaller numbers of the Daubentons or River Bats arrived much later as darkness set in to trawl for insects low over the water. It was this species that I thought could be most adversely affected by artificial illumination of the water surface. For this reason we agreed with the lighting engineer to only light a small part of the water surface (less that 25%), retain a dark edge along the woodland bank and limit lighting only to the hours of filming. The lighting engineer was very interested and extremely accommodating to our requests. I monitored the lighting on the 26th July 2012 and found that the Pipistrelle bats were actively foraging for insects attracted by the lights. Jade monitored throughout the event and believes that the Daubentons did stick to the unilluminated areas of the lake as predicted.
Iain Webb from the Wildlife Trust recently led a bat walk at the hall and I understand recorded good number of both Pipestrelle and Daubentons foraging over the lake.
4) Bird strike, particularly the Kingfisher
I advised against the use of clear Perspex or glass with a backdrop of vegetation behind. This was due to potential bird strikes should they perceive a clear flight path on a traditional route. On our visit on the 26th July 2012, Jade and I saw that Perspex had been used and requested that when the set was not active, that a curtain or screen be erected. This was actioned immediately and Jade monitored this throughout the event. No bird strikes were recorded.
This issue has raised the profile of the ecological implications of the Folk Festival. The parks teams have requested that a site-wide ecological assessment be prepared for both Cherry Hinton Hall and Coldhams Common Local Nature Reserve prior to next year’s event.