Limiting the spatial extent of artificial lighting along ecological corridors: Implications for outdoor lighting planning recommendations

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Context and methodology of an ongoing systematic review

During my PhD, I got involved in the COST LoNNe (“Loss of the Night Network”; investigating the impacts of light pollution on ecosystems, human health and stellar visibility, and at elaborating recommendations for sustainable outdoor lighting planning. In this context, I have started with 3 collaborators of the network, Dr. Sibylle Schroer, Dr. Franz Hölker and Dr. Roy van Grunsven, a systematic review on the effects of artificial lighting on biodiversity, in order to propose effective lighting management recommendations for policy makers and stakeholders.
This project is still under progress and is expected to be published as a policy paper at the end of 2017. The number of publications on the ecological impacts of light pollution on biodiversity has grown exponentially in the last fifteen years (Figure 3). So far, I have already extracted the literature from scientific databases (See Box 1 for details on the methodology) and classified the biological impacts of artificial lighting on bats, birds and insects which are detailed in the following section and are synthesized in the Table 1. The next step is to extract minimum threshold values for different lighting parameters to elaborate evidence-based recommendations for outdoor lighting planning (details in the General Discussion).

Alterations of species circadian and seasonal cycles

The natural alternation between day and night is an environmental cue that regulates the life cycles of both diurnal and nocturnal organisms. By inducing a large scale loss of the nighttime, artificial lighting generates major disruptions of species circadian rhythms (Navara & Nelson 2007; Robertson et al. 2010; Gaston et al. 2013; Dominoni et al. 2016). Nighttime artificial lighting inhibits melatonin secretions and alters vital biological functions such as sleep and biolo-gical clock regulations (Dominoni et al. 2013c; Durrant et al. 2015; de Jong et al. 2016).
Exposed passerine birds populations appear to advance their onset of daily activity (dawn chorus) from 10 to 30 minutes before sunrise, and to delay their cessation of activity 20 minutes after sunset (Nordt & Klenke 2013; Da Silva et al. 2015a; de Jong et al. 2016). Similarly, the time of emergence of female bats from maternity roosts can be significantly delayed by illuminating the monument they roost in (Downs et al. 2003; Boldogh et al. 2007). This has important implications for the reproductive success of maternities as it can decrease the growth of juveniles (Boldogh et al. 2007), and it may alter the fitness of reproductive females which can miss the peak abundance of insects at dusk (Jones & Rydell 1994).

Alteration of species movements and spatial distribution

Additionally to the impacts of light pollution on species rhythms of activity, the spatial distribution of nighttime artificial light in the landscape can also dramatically influence species movements and distributions. These impacts are of particular importance for nocturnal species because they use the nightscape to move, forage, and reproduce (Hölker et al. 2010b). The case of nocturnal insects is particularly extreme, as they present a “flight-to-light behaviour” inducing a massive attraction and trap of individuals toward light sources (Altermatt et al. 2009; van Grunsven et al. 2014). This generates an accumulation of insect biomass in illuminated patches and induces insect depletion in surrounding dark areas (Eisenbeis 2006). Insect abundance and richness are key components of ecosystems as they forms the basis of most food webs (Conrad et al. 2006). Thus, the shifts in the spatial distribution of insects induced by artificial lighting likely engender cascading impacts for their predators, as it generates high quality foraging patches for light-tolerant species, while decreasing the size and quality of dark areas for light-sensitive species. As an example, the response of microchiropteran bats (insectivorous) to nighttime artificial lighting vary among species according to their foraging strategy and flight abilities (Jones & Rydell 1994). Fast-flying bat species that forage insects at dusk in the open air, such as  Pipistrellus spp. and Nyctalus spp., appear to exploit illuminated niches that present new sources of high quality and predictable foraging opportunities (Rydell 1992; Blake et al. 1994a; Lacoeuilhe et al. 2014). In contrast, slow-flying species that prey on insects in cluttered vegetation, such as Rhinolophus spp. and Myotis spp., avoid any source of artificial lighting (Rydell 1992; Kuijper et al. 2008b; Stone et al. 2009, 2012), probably because of an intrinsic perception of increased predation risk (Jones & Rydell 1994). Hence, light pollution likely modifies landscape use and spatial distribution of nocturnal species by inducing habitat loss for light-sensitive species, and habitat gain for light-tolerant ones.

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Levers of actions to limit light pollution impacts

Streetlights along roads, pavements and streets are the most important sources of light pollution They represent 38% of brightly lit areas in Birmingham (Hale et al. 2013), and 31.6 % of zenith directed light pollution in Berlin (Kuechly et al. 2012). Most of the studies so far investigating the effects of nighttime artificial lighting on biodiversity have focused on the effects of the type of streetlamps (defined by its spectrum; Box 2; Figure 4; Table 2) on physiological and behavioral responses of organisms. In the European Union, the most common types of streetlamps used are sodium vapor lamps (High Pressure Sodium, HPS and Low Pressure Sodium, LPS), Metal Halide (MH) and High Pressure Mercury vapor lamps (HPM) representing respectively 37, 36, and 27 % sales for the period 2004-2007 (EC, 2011). However, since the European Eco-Design Directive (245/2009), HPM lamps are being progressively phased out from the market because of their low energetic efficiency (Table 2). This change occurs concomitantly with the increased cost-effectiveness of energy-efficient Light Emitting Diodes (LEDs), representing so far approximately 7 % of the European market (Zissis & Bertoldi 2014). HPM, MH and standard white-LEDs lamps have broad-spectrum emissions, with an important peak of energy in the blue range (Correlated Color Temperature (CCT) > 3000 K; Figure 4; Table 2).
HPS lamps also have broad-spectrum emissions although they present an important peak of energy in the orange-red range (CCT < 2700 K; Figure 4; Table 2). In contrast, LPS are narrowspectrum emitting lamps with a single peak of energy emitted in the yellow range (CCT = 1807 K; Table 2). HPM, MH and HPS lamps emit energy in the UV range (although HPS emit relatively less UVs than HPM and MH), contrary to LEDs and LPS lamps.

Table of contents :

GENERAL INTRODUCTION
1. Light pollution in a changing world
2. The ecological impacts of light pollution on biodiversity
2.1. Context and methodology of an ongoing systematic review
2.2. Alterations of species circadian and seasonal cycles
2.3. Alteration of species movements and spatial distribution
2.4. Cascading impacts on biological communities
2. Levers of actions to limit light pollution impacts
2. Knowledge gaps and plan of the thesis
CHAPTER 1: Characterization of the landscape-scale effects of light pollution on bats relative to other land-use pressures in France
Introduction
Article 1: Azam C, Le Viol I, Julien J-F, Bas Y, Kerbiriou C. 2016. Disentangling the relative effect of light pollution, impervious surfaces and intensive agriculture on bat activity with a national-scale monitoring program.
Online Appendices
Discussion & Perspectives
CHAPTER 2: Limiting the temporal extent of artificial lighting to reduce the negative impacts of outdoor lighting on bat activity
Introduction
Article 2: Azam C, Kerbiriou C, Vernet A, Julien JF, Bas Y, Plichard L, Maratrat J, Le Viol I. 2015. Is part-night lighting an effective measure to limit the impacts of artificial lighting on bats? Global Change Biology 21:4333–4341.
Online Appendices
Discussion & Perspectives
CHAPTER 3: Limiting the spatial extent of artificial lighting along ecological corridors: Implications for outdoor lighting planning recommendations
Introduction
Article 3: Azam C, Le Viol I, Bas Y, Zissis G, Vernet A, Julien JF, Kerbiriou C. 2017. Evidence for distance and illuminance thresholds in the effects of artificial lighting on bat activity (Ready for submission).
Online Appendices
Discussion & Perspectives
GENERAL DISCUSSION
1. Impacts of light pollution on biodiversity: a multi-scale issue
2. Light pollution as an indicator of urbanization process
3. Implications for public outdoor lighting planning
REFERENCES

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