No abstract

Ecologists have long studied the critical role of natural light in regulating species interactions, but, with limited exceptions, have not investigated the consequences of artificial night lighting. In the past century, the extent and intensity of artificial night lighting has increased such that it has substantial effects on the biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting on the behavior and community ecology of species are less well recognized, and constitute a new focus for research in ecology and a pressing conservation challenge.

28Human activities have caused a near-ubiquitous and evolutionarily-unprecedented increase in 29 environmental sound levels and artificial night lighting. These stimuli reorganize communities 30 by interfering with species-specific perception of time cues, habitat features, and auditory and 31 visual signals. Rapid evolutionary changes could occur in response to light and noise, given their 32 magnitude, geographical extent, and degree to which they represent unprecedented 33 environmental conditions. We present a framework for investigating anthropogenic light and 34 noise as agents of selection, and as drivers of other evolutionary processes, to influence a range 35 of behavioural and physiological traits, such as phenological characters and sensory and 36 signalling systems. In this context, opportunities abound for understanding contemporary and 37 rapid evolution in response to human-caused environmental change. The overcast night sky radiance in urban areas has been found to be as much as four orders of 55 magnitude larger than in natural settings (Figure 1) [5]. Similarly, increased noise levels affect a 56 sizable proportion of the human population. In Europe for instance, 65% of the population is 57 exposed to ambient sound levels exceeding 55 dB(A) [6], roughly equivalent to constant rainfall. 58Of the land in the contiguous U.S., 88% is estimated to experience elevated sound levels from 59 anthropogenic noise (Figure 1) [7]. These effects are not limited to terrestrial environments; 60 ocean noise levels are estimated to have increased by 12 decibels (an ~16-fold increase in sound 61 intensity) in the past few decades from commercial shipping alone [8], while an estimated 22% 62 of the global coastline is exposed to artificial light [3] and many offshore coral reefs are 63 chronically exposed to artificial lighting from cities, fishing boats, and hydrocarbon extraction 64 [9]. 65The changes in light at night and noise levels are occurring on a global scale similar to 66 well-recognized ecological and evolutionary forces such as land cover and climate change. In 67 4 parallel with research involving climate change [10], much of our understanding of organismal 68 response to noise and light is restricted to short-term behavioural reactions. Organismal 69 responses might be associated with tolerance to these stimuli in terms of habitat use [11,12] Status of research on anthropogenic light and sound in ecology 98Night lighting and noise are highly correlated in many landscapes (e.g., [21]). It is critical to 99 understand whether the selective pressures these stimuli exert are additive, synergistic (Figure 2), 100 or if they mitigate one another. Few studies have examined the influence of each simultaneously 101 (e.g., [21]). In one study, flashing lights combined with boat motor noise suppressed antipredator 102 behaviour in hermit crabs (Coenobita clypeatus) more so than noise alone [22]. Future research 103 should quantify both light and sound simultaneously in the same population. Existing r...

Nightsat is a concept for a satellite system capable of global observation of the location, extent and brightness of night-time lights at a spatial resolution suitable for the delineation of primary features within human settlements. Based on requirements from several fields of scientific inquiry, Nightsat should be capable of producing a complete cloud-free global map of lights on an annual basis. We have used a combination of high-resolution field spectra of outdoor lighting, moderate resolution colour photography of cities at night from the International Space Station, and high-resolution airborne camera imagery acquired at night to define a range of spatial, spectral, and detection limit options for a future Nightsat mission. The primary findings of our study are that Nightsat should collect data from a near-synchronous orbit in the early evening with 50 to 100 m spatial resolution and have detection limits of 2.5E 28 Watts cm 22 sr 21 mm 21 or better. Although panchromatic low-light imaging data would be useful, multispectral low-light imaging data would provide valuable information on the type or character of lighting; potentially stronger predictors of variables, such as ambient population density and economic activity; and valuable information to predict response of other species to artificial night lighting. The Nightsat mission concept is unique in its focus on observing a human activity, in contrast to traditional Earth observing systems that focus on natural systems.