About this good practice
Artificial light has a negative impact on the roosting and foraging activities of bats. 29 chiropteran species are present in the NCA territory, of which 11 are particularly sensitive to light disturbance (regional conservation status is very high for 2 species and high for 4 species). Light disturbance occurs when the locations of street lights, bat roosting sites and/or bat corridors overlap. Street lights were mapped, and locations of roosting sites were provided by the regional bat group (GCP). Green corridors were used as surrogates for the bat corridors. The mapping exercise revealed eleven zones of light disturbance, 5 of which are of high priority given the conservation status of the species present. The municipalities subsequently employed different light pollution mitigation measures as recommended by the GCP: street light extinction periods, reorientation of the lights and changes in their height (in order to limit the diffusion effect), spectrum mitigation (reduction of blue light), avoidance of lighting vegetation and rock walls, and the creation of light barriers to protect particularly sensitive zones. A specific technical guidance document was printed and distributed to NCA municipalities, recommending impact monitoring in areas where light extinction is implemented and in control areas. So far 3 municipalities have carried out monitoring. In future a ‘dark ecological network’ will be scaled up at NCA scale in collaboration with CEREMA.
Investments: 700€ per lighting spot
Human resources: 20 to 30% of the salary of an agent dedicated to the thematic per year.
Evidence of success
Quantifiable data only available for Cagnes sur Mer municipality at this stage (analysis ongoing elsewhere): The experimentation suggests that fragile bat specied benefit of new territories from which they were previously excluded due to their aversion of light, as well as from food resources previously inaccessible.
Annual energy savings: 41950 kWh, which is the equivalent to the energy consumption of 9 homes over 1 year, i.e. about 6300€ of savings per year.
Potential for learning or transfer
This GP appears to be interesting to learn from, particularly if scientific monitoring establishes a good relation between mitigation measures and species activities. It is transferable to other sites but there is a need for complete and precise preliminary studies to adapt mitigation measures to local circumstances. The mitigation measures are quite easy to put in place and develop.