REVIEW: Reducing the ecological consequences of night‐time light pollution: options and developments

Abstract

1. Much concern has been expressed about the ecological consequences of night-time light pollution. This concern is most often focused on the encroachment of artificial light into previously unlit areas of the night-time environment, but changes in the spectral composition, duration and spatial pattern of light are also recognized as having ecological effects.2. Here, we examine the potential consequences for organisms of five management options to reduce night-time light pollution. These are to (i) prevent areas from being artificially lit; (ii) limit the duration of lighting; (iii) reduce the ‘trespass’ of lighting into areas that are not intended to be lit (including the night sky); (iv) change the intensity of lighting; and (v) change the spectral composition of lighting.3. Maintaining and increasing natural unlit areas is likely to be the most effective option for reducing the ecological effects of lighting. However, this will often conflict with other social and economic objectives. Decreasing the duration of lighting will reduce energy costs and carbon emissions, but is unlikely to alleviate many impacts on nocturnal and crepuscular animals, as peak times of demand for lighting frequently coincide with those in the activities of these species. Reducing the trespass of lighting will maintain heterogeneity even in otherwise well-lit areas, providing dark refuges that mobile animals can exploit. Decreasing the intensity of lighting will reduce energy consumption and limit both skyglow and the area impacted by high-intensity direct light. Shifts towards ‘whiter’ light are likely to increase the potential range of environmental impacts as light is emitted across a broader range of wavelengths.4. Synthesis and applications. The artificial lightscape will change considerably over coming decades with the drive for more cost-effective low-carbon street lighting solutions and growth in the artificially lit area. Developing lighting strategies that minimize adverse ecological impacts while balancing the often conflicting requirements of light for human utility, comfort and safety, aesthetic concerns, energy consumption and carbon emission reduction constitute significant future challenges. However, as both lighting technology and understanding of its ecological effects develop, there is potential to identify adaptive solutions that resolve these conflicts.

Artificial Light at Night Reduces Daily Energy Expenditure in Breeding Great Tits (Parus major)

“…Over the last decades, light sources, especially those of street lamps, have been undergoing a general change from narrow to broad spectrum light. A recent example is the widespread shift to LED lights (Gaston et al, 2012;Bennie et al, 2014). However, despite a recent body of studies that examined the ecological consequences of ALAN (Rich and Longcore, 2006;Migaud et al, 2007;Davies et al, 2013;Spoelstra et al, 2015), little is known about how different light spectra might affect the behavioral and physiological responses of wild species.…”

LED lighting increases the ecological impact of light pollution irrespective of color temperature

“…The biological effect of a shift toward a more ''white-light night'' (sensu Gaston et al 2012) has not been studied in detail, but direct evidence of biological impacts is mounting (Stone et al 2012), and comparisons of visual pigment absorbance spectra with the emission spectra of municipal light sources suggests indirectly that such impacts may be widespread among terrestrial animals . Gaston et al (2012) proposed that the ecological consequences of light pollution could potentially be reduced by avoiding critical regions within the spectrum. Currently available municipal and industrial-scale white LED lights are based on monochromatic blue LEDs (Krames et al 2007).…”

Out of the Dark: Establishing a Large-Scale Field Experiment to Assess the Effects of Artificial Light at Night on Species and Food Webs

“…Artificial light at night (ALAN) has led to increased light pollution [3] and to potentially important, but largely neglected, impacts on biodiversity [4][5][6]. While night-time lights have been used to develop indicators of human well-being [7], little is known about the detrimental effects that ALAN may have on terrestrial, freshwater, and riparian ecosystems [8][9][10][11].…”