Modelling of the nocturnal ecological continuum of the Geneva basin

The increase in artificial light in recent decades has led to a general awareness of the harmful consequences of light pollution on biodiversity, but also on human health.

However, artificial light is still rarely taken into account in the development of ecological networks. There is currently no standard method for incorporating this obscurity factor into ecological network modelling.

We propose a methodology for identifying the nocturnal continuum, also called the black frame, through an approach based on the automated extraction of light sources from night orthophotography and the modelling of their visibility in a territory. The model is applied to the cross-border region of the Geneva basin in Switzerland and allows the integration of the obscurity factor into existing ecological networks.

^{Visibility of light sources in the Geneva basin. (Ranzoni et al., 2019)}

Although the analysis does not take into account metric lighting data, a visual basin analysis allows for an initial large-scale mapping of the nocturnal continuum and highlights areas with very low light pollution.

This study, supported by the Cantonal Office for Agriculture and Nature, was carried out in partnership with the Institute of Environmental Sciences of the University of Geneva, and is part of the Geneva 2030 Biodiversity Strategy.