Assessing the effects of artificial light at night on biodiversity across latitude – Current knowledge gaps

Abstract

Aim: Exposure to artificial light at night (ALAN) is a risk factor for organisms.Considering the spread and increasing intensity of night brightness across the globe, and the key role of light at all biological levels, alterations of ecosystems are ex-pected. Yet, we cannot predict the severity of the effects of ALAN in several biomes because little information is available outside the temperate zone. We reviewed current knowledge and identified traits that could be targeted to fill this knowledge gap in order to contribute to the elaboration of a biogeographical framework for the study of ALAN at the global scale. Location: Global.Time period: Current and next decades. Methods:We analysed the latitudinal variation in ALAN and focused on environmental factors that vary with latitude but that have been overlooked. We reviewed biological traits that exhibit latitudinal variation and depend on light and photoperiod and compiled information about the predicted changes in human demography and road networks across different world regions. Results:Cloud cover amplifies ALAN far away from urbanized areas. Because of the higher frequency of overcast sky nights, exposure effects may be stronger both at high latitudes and across a large fraction of the intertropical zone, although at different times of the year. Intertropical biomes host the largest fraction of global biodiversity. Although currently they are not the most exposed to ALAN, their human populations are growing, and urbanized areas and road networks are expanding.Hence, ALAN could have strong ecological consequences, with cloud cover as an aggravating factor. Perspectives: Knowledge gaps currently limit our ability to predict the effects of ALAN in different biomes. Therefore, it will be important to start investigating the consequences of this novel environmental factor across the globe, in order to develop a relevant theoretical framework. K E Y W O R D SALAN, biogeography, exposure, global change, intertropical, latitude, light pollution | 405 SECONDI Et al.

Effects of artificial light at night on the leaf functional traits of freshwater plants

“…Artificial light at night (ALAN hereafter) is now recognised as an anthropogenic pollutant of concern, jeopardising biodiversity at a global scale (Gaston et al., 2015; Guetté et al., 2018; Hölker et al., 2010; Sanders et al., 2020; Secondi et al., 2020). Falchi et al.…”

11 Pressing Research Questions on How Light Pollution Affects Biodiversity

“…To give an example, high sensitivity to light in the eyes of North American bird species has been associated with a greater advancement of reproductive timing in response to light exposure, possibly leading to phenological mismatches (Senzaki et al, 2020). Elucidating biological traits that predicate sensitivity to ALAN is therefore critical for identifying ALAN-vulnerable species around the world (Secondi et al, 2020).…”

“…Light-dark cycles vary along latitudinal gradients (Hut et al, 2013), hence species traits that predicate sensitivity to ALAN are also expected to vary with latitude (Secondi et al, 2020). While birds in lower latitudes started to sing earlier when exposed to ALAN, in high latitudes the seasonal increase of natural light can mask ALAN effects on the onset of bird song (Da Silva and Kempenaers, 2017).…”

“…On the other hand, different latitudes harbor different ecosystems and hence species inhabiting them. Yet, the extent to which photoperiod and climate modulate exposure to ALAN at a given latitude is unknown (Secondi et al, 2020). Also, ecosystems interact and thus changes in one ecosystem due to ALAN will likely also impact linked ecosystems (e.g., Manfrin et al, 2017; Figure 2C).…”

Large-scale deregulation of gene expression by artificial light at night in tadpoles of common toads

“…Photoperiod is one of the major environmental cues that regulates biological processes in living organisms (Longcore & Rich, 2004;Ouyang et al, 2017) and allows them to anticipate daily and seasonal changes and adapt their biochemical, physiological and behavioural activities. In the last century, artificial light at night (ALAN), generated by the surge in urbanized areas and transport infrastructures (Gaston et al, 2013), has dramatically expanded worldwide (Falchi et al, 2016) and endangered biodiversity on the global scale (Gaston et al, 2015;Guetté et al, 2018;Hölker et al, 2010;Secondi et al, 2019).…”