Restrict timing of lighting

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

38%
Certainty

20%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Dimming or switching off artificial lighting when not in use or at certain times of night (e.g. when bats are most active) may reduce the impact on bats. A study in the UK found that streetlights would need to be switched off until midnight to coincide with peak activity of the greater horseshoe bat Rhinolophus ferrumequinum (Day et al. 2015).

Day J., Baker J., Schofield H., Mathews F. & Gaston K.J. (2015) Part-night lighting: implications for bat conservation. Animal Conservation, 18, 512–516.

Study locations

Key messages

One study evaluated the effects of restricting the timing of lighting on bat populations. The study was in France .

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in France found that turning off streetlights for part of the night resulted in mixed results for activity (relative abundance), depending on bat species, when compared with leaving streetlights switched on all night.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, paired sites study prior to 2015 at 36 paired rural sites in France (Azam et al 2015) found that turning off street lights for part of the night resulted in higher activity for two bat species, lower activity for one bat species and similar activity for five bat species when compared with leaving street lights switched on all night. The average number of bat passes/night was higher with part-night lighting than full-night lighting for Plecotus spp. (part-night lighting: 2.3; full-night lighting: 0.6) and common noctules Nyctalus noctula (data not reported), but lower with part than full-night lighting for common pipistrelles Pipistrellus pipistrellus (part-night lighting: 515; full-night lighting: 1,130). Activity was similar under both light treatments for Kuhl’s pipistrelles Pipistrellus kuhlii, Nathusius’ pipistrelles Pipistrellus nathusii, Leisler’s bats Nyctalus leisleri, serotine bats Eptesicus serotinus and Myotis spp. (see original paper for detailed results). Each of 36 pairs of sites had one site with street lighting (high-pressure sodium lights, 10–99 lux) and one unlit control site within similar habitats. Street lights were either turned off for part of the night (between midnight and 05:00 h, 24 sites) or were left on for the full night (12 sites). Each of 36 pairs was sampled simultaneously using bat detectors for one full night between May and August (year not reported).
Study and other actions tested
Referenced paper
Azam C., Kerbiriou C., Vernet A., Julien J.-F., Bas Y., Plichard L., Maratrat J. & Le Viol I. (2015) Is part-night lighting an effective measure to limit the impacts of artificial lighting on bats. Global Change Biology, 21, 4333-4341.

Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2021) Bat Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Bat Conservation

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Restrict timing of lighting Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
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Leave bat roosts and roost entrances unlit Action Link	Beneficial	5	Synopsis Link