Bats are nocturnal animals and are adapted to low-light conditions. This means that most bat species can find artificial lighting to be very disturbing. Artificial lights shining on bat roosts, their access points and the flight paths away from the roost must always be avoided.
If it is considered necessary to illuminate a building known to be used by roosting bats, the lights will need to be switched off at bat emergence time and during peak bat activity times. Or better still, it is usually straightforward to ensure that the light does not fall on the roost access point or the flight line away from the roost used by bats. Celebratory lighting of buildings should be limited to special occasions.
Bats and their roosts are all protected by law and bats should always be taken into account when lighting is being considered.
BCT Interim Guidance: artificial lighting and wildlife
An interim guidance note has been produced following the outputs from the 2014 European Symposium detailed below. This will be updated to reflect research developments in this area, however it currently provides recommendations to help minimise the impact of artificial lighting.
Artificial Light and Wildlife Symposium 2014: determining solutions for practitioners
The Bat Conservation Trust in partnership with Arup hosted a European Symposium on 20 & 21 March 2014.
The syposium was fully described with presentations from researchers and professionals across Europe. The presentations from the symposium are now available to view online.
Unfortunately, some of the presentations cannot be circulated owing to the sensitivity of unpublished data contained within them. This data will be used to update the technical guidance note (above) in due course.
Bats and Lighting: overview of current evidence and mitigation
BCT is working with researchers at the University of Bristol to develop a comprehensive overview of current evidence and mitigation for bats. This publication is now available.
Additional reference documents and websites:
- The Institute for Lighting Professionals Guidance for the Reduction of Obtrusive Light
- Buglife reports on the Impact of Artifical Lighting on Invertebrates
- Life+ Life at Night project
What else are we doing?
As more bat workers have access to light meters, the National Bat Monitoring Programme colony counts now allow the opportunity to include information about the lux levels measured during bat emergence.
Those carrying out NBMP car surveys are being asked to record the type of street lighting along their route. All this data being gathered will be important in identifying trends that will support current research.