Bats and lighting design

Bats and lighting design

From household extensions to greenfield residential development, where there is habitat suitable for bats there is a growing acknowledgement within planning authorities of the need to ensure that important areas for bats are protected from light pollution. Bats and lighting design are therefore often significant considerations when considering site capacity and optimising site layout.

 

What is the issue?

Bats and their roost sites are protected by both national and international legislation. The Wildlife and Countryside Act 1981 protects all bats from ‘intentional’ or ‘reckless’ disturbance. Lighting of a roost can have several impacts, as well as causing disturbance, it can delay emergence of some species (meaning they miss the peak abundance of insects), it may also lead to abandonment of the roost or even act to entomb bats inside. Lighting of currently dark areas that are used by bats for navigating across the countryside can also make it difficult for this species to reach preferred foraging grounds, reducing their resilience and increasing risk of predation or, if there isn’t an alternative route, they may become isolated from their foraging grounds altogether.

 

The development response

Many planning authorities now routinely require that important dark corridors are protected and that lighting assessments are undertaken / lighting plans prepared to demonstrate that this can be achieved.

The most straightforward option when devising lighting strategies is to avoid any increase in light levels from artificial lighting on any key habitats or features (typically linear features such as hedgerow, riparian habitats or woodland).  This is most rigorously applied in areas that are identified by Development Plan Policy or nature conservation designations as important for nearby major roosts (such as the supporting habitat ‘bands’ that are identified for the North Somerset and Mendip Bat Special Area of Conservation, SAC). This can be challenging to achieve and we recommend that this should be considered at an early stage of site capacity review and layout design.

In other areas the requirement is less stringent and the use of mitigation methods may be required to reduce (rather than avoid completely) the amount of light spill onto bat habitats and features.

 

Bats and lighting design

Examples of suitable mitigation methods include the use of:

  • buffer zones to separate habitats/features from the lighting source;
  • LED luminaires due to their lower intensity and dimming capability;
  • warm white (i.e. more yellow/orange colour) light to reduce blue light component and subsequent attraction of insects;
  • low level illuminated lights to prevent upward light spill and light spill onto boundary features/vegetation and adjacent land;
  • Passive Infrared Sensors (PIR) on security lighting, therefore they will only be activated as and when required for safety purposes;

In 2018 the Institute of Lighting Professionals (ILP) launched a practical guide about taking bats into consideration when designing lighting schemes, more information can be found here.

 

An illuminating experience (… sorry)

Helpfully, application of measures to minimise effect on retained ‘dark areas’ can also help to minimise adverse effects on amenity in ‘dark landscapes.’  Our ecologists increasingly work alongside lighting consultants and our in-house landscape team to maximise the benefits of a carefully designed lighting scheme, to demonstrate a well-considered scheme to the local planning authority and to the benefit of the end-user (see also, our news item ‘Night Time LVIA’).

Landmark’s ecology team is experienced in balancing commercial and design needs with wildlife policy and law.  If we can be of any assistance with matters relating bats and lighting, please do contact us on 0117 9230455 or at enquires@thelandmarkpractice.com.