ALATALAN – Assessing the importance of LATitude on the modulation of Artificial Light At Night on biodiversity

ALAN affects most of the European continent and negatively affect biodiversity, ecosystem services and human health. Addressing ALAN is also a societal challenge that requires to balance biodiversity protection and societal demands for night-time lighting. Finally, ALAN is an economic issue as public lighting represents a large part of municipality budgets for energy expenses. Whether ALAN affects with the same intensity biodiversity everywhere on Earth is crucial information. Answering this question can help to find the right balance for policy makers and local authorities. Most studies on ALAN impacts on organisms focused on the temperate zone but the generated effects for a given exposure level are expected to change with latitude because latitude determines the photoperiod regime (annual variation of daylength). Photoperiod, the main synchroniser of biological activity rhythms, is constant close to the Equator and vary wildly in boreal and Arctic regions. Photoperiod stability is thus expected to influence the sensitivity of organisms to ALAN. The importance of latitude (hence photoperiod) on biological rhythms and their evolution is well described. Daily and seasonal biological rhythms can be adjusted to the local conditions to ensure an optimal timing of activities. However, there is no theoretical framework for predicting the severity of the effects of ALAN nor to identify which process is the most likely disrupted at a given latitude. The strongest alterations may concern different processes even between the northern and southern edges of Europe. LEHNA team has recently published an article on this issue, proposing general hypotheses. The current project seeks to clarify and formalize these hypotheses by integrating knowledge from chronobiology into ALAN studies. Reciprocal stays between Norway and France will allow this work and contribute to consolidate the building of a European consortium of European teams to address this issue