[2015] TRAMENOIRE - Program of study and research for the development of the black grid of the Lille agglomeration

In Europe, all bat species are nocturnal. They are particularly sensitive to disturbances related to light pollution that fragment their territory. As a result, they adapt and lengthen their flight routes, they are deprived of many hunting grounds, too bright, and see the remaining dark areas impoverished by insects, attracted by artificial light sources. In some cases, survival and reproductive success of individuals are compromised.

The European Metropolis of Lille renews its public lighting park and takes the opportunity to reflect on the establishment of a black grid to improve the connectivity of dark spaces. It relies for this on a multidisciplinary research consortium.

The TRAMENOIRE project seeks to answer three questions:

    Can we build on the existing network of corridors for the development of a local black network?
    What is the current state of nocturnal ecological connectivity at the scale of the metropolis?
    Can this connectivity be improved by reducing light intensity?

Recordings, analyzes and modelizations according to gradients of luminous intensity, urbanization and tree elements made it possible to understand the influence of light pollution on the spatial distribution and the activity of the chiroptera then to predict and map the distribution expected from four species [1], to finally recommend concrete conservation actions. Four lighting scenarios (reduction of light intensity in urban parks, motorways, in municipalities with less than 10,000 inhabitants and / or more than 10,000 inhabitants) were tested to achieve the most functional corridors possible. for chiroptera.

And for men? Are these scenarios accepted by locals and city professionals? The social aspect of the TRAMENOIRE project also aims to reinforce the concept of black grid and optimize its operational implementation. The study of its perception by the public was therefore essential.

An analysis carried out on several municipalities shows that the concept of black frame in France is still very young and poorly defined. The results of survey of the population show that a priori, the black frame is socially acceptable.

The surveys reveal that nocturnal wildlife residents are well aware of the fact that they are also aware of the diversity of species with which they live together in urban and peri-urban areas. While nocturnal species are generally well appreciated, the bat is highly indifferent and is of interest to less than half of the respondents.

The vast majority of respondents agree on the harmful effects of the absence of night on the nocturnal fauna. In general, city dwellers say they are willing to give up the comfort that public lighting gives them to protect these species from the harmful effects of artificial light.

The results of the study highlight the interest of associating the residents from the beginning of the projects of setting up a black frame. It also seems interesting to experiment changes in public lighting to study the effects on biodiversity and to study the social acceptability of innovative modes of public lighting put in place during the creation of a black frame.