Bats & Lighting

Bats and Lighting - Mitigation

Bat surveys
Bats can be very sensitive to light and could potentially avoid areas if they are well lit. Any new lighting schemes within your project should be designed to avoid light spillage onto buildings, hedgerows, trees or adjacent habitats that bats may use. Appropriate lighting options will prevent a negative impact on bats using the habitats on site and should be approved by a suitably qualified ecologist. 

Screen planting and vegetation

This can help screen light pollution considerably. For example, light pollution can be made worse when vegetation is removed. Tree canopies and their overhang near water bodies should be retained as they create dark shadows favoured by foraging bats.  

Type of lighting

  • The impact on bats can be minimised by:
  • Using low-pressure sodium lamps instead of high pressure sodium or mercury lamps 
  • Fitting mercury lamps with UV filters 
  • Maintaining the brightness as low as legally possible
  • Limiting the times during which the lighting can be used to provide some dark periods
  • Directing the lighting to where it is needed to avoid light spillage
  • Minimising upward lighting to avoid light pollution
Light can be restricted to certain areas by fitting hoods which direct the light below the horizontal plane, at an angle less than seventy degrees. Limiting the height of lighting columns to eight metres and directing light at a low level reduces the ecological impact of light.

Information can be factored into a design to calculate vertical illuminance. Data such as bat flight paths and roosting/hibernation areas may also be incorporated. The results from these calculations are used to adjust the lighting column positions and heights. 

Light Curfews

Generally, within the months May-October, areas used by bats should not be illuminated outside after 8.30pm. If it considered necessary to illuminate a building where roosting or commuting bats pass by, the lights will need to be switched off at bat emergence times and during the periods of peak bat activity. 

Roads and trackways in areas considered important for foraging bats should contain stretches left unlit to avoid isolation of bat colonies.

Southern Office - Farnham, Surrey

Helen Cavilla
01252 413 221
07701 370 762

Laura Ashford
01252 413 221
07525 134 803

South West Office - Shaftesbury

Michael Cummings
01252 413 221
07748 843 842
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