Human alteration of natural light cycles: causes and ecological consequences

Abstract

Artificial light at night is profoundly altering natural light cycles, particularly as perceived by many organisms, over extensive areas of the globe. This alteration comprises the introduction of light at night at places and times at which it has not previously occurred, and with different spectral signatures. Given the long geological periods for which light cycles have previously been consistent, this constitutes a novel environmental pressure, and one for which there is evidence for biological effects that span from molecular to community level. Here we provide a synthesis of understanding of the form and extent of this alteration, some of the key consequences for terrestrial and aquatic ecosystems, interactions and synergies with other anthropogenic pressures on the environment, major uncertainties, and future prospects and management options. This constitutes a compelling example of the need for a thoroughly interdisciplinary approach to understanding and managing the impact of one particular anthropogenic pressure. The former requires insights that span molecular biology to ecosystem ecology, and the latter contributions of biologists, policy makers and engineers.

The biological impacts of artificial light at night: the research challenge

“…Given the nature of such images, it is challenging to use these to make some categorical quantification of the extent of ALAN, although it is plainly much more widespread than urban infrastructure alone, mainly because of the skyglow effect. One estimate that accounted explicitly for the effects of skyglow was that 18.7% of the global land area experienced ALAN [12], another based more directly on satellite imagery that 11.4% of terrestrial and 0.2% of marine areas of the globe experienced ALAN [11], and another that ALAN is increasing at around 6% per annum with huge geographical variation (0-20%; [14]). …”

“…Second, ALAN is introducing light with a spectrum that is different from those of sunlight, moonlight or starlight [11]. The spectrum of ALAN depends fundamentally on the kind of lighting device that is being used, ranging from narrow (e.g.…”

“…On the ground this disruption of natural patterns of light takes two principal forms [11]. First, light has been introduced in places, times and at intensities at which it does not naturally occur.…”

Changes in Light Pollution and the Causing Factors in China’s Protected Areas, 1992–2012

“…Directly, it represents a threat to biodiversity [4] and can alter species distribution, community structure, and, possibly, ecosystem functions and processes [5]. Indirectly, light pollution has strong synergies and interactions with other pressures on biodiversity, including habitat fragmentation and climate change [6].…”

Statistical modelling and satellite monitoring of upward light from public lighting

“…Notwithstanding the recent advances in this field a growing body of research has revealed the accelerated pace at which light pollution is affecting different aspects of our lives. Light pollution -the alteration of the natural levels of nighttime darkness due to artificial lighting-shows an increasing trend and its farreaching consequences have been reported in such diverse fields as basic science [1][2][3] , energy management [4][5][6][7] , ecology [8][9][10][11] and human health [12][13][14][15][16] , to mention a few.…”