Mitigating the impact of artificial lighting on bats

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.