Abstract
The disruption to natural light regimes caused by outdoor artificial nighttime lighting has significant impacts on human health and the natural world. Artificial light at night takes two forms, light emissions and skyglow (caused by the scattering of light by water, dust and gas molecules in the atmosphere). Key to determining where the biological impacts from each form are likely to be experienced is understanding their spatial occurrence, and how this varies with other landscape factors. To examine this, we used data from the Visible Infrared Imaging Radiometer Suite (VIIRS) day/night band and the World Atlas of Artificial Night Sky Brightness, to determine covariation in (a) light emissions, and (b) skyglow, with human population density, landcover, protected areas and roads in Britain. We demonstrate that, although artificial light at night increases with human density, the amount of light per person decreases with increasing urbanization (with per capita median direct emissions three times greater in rural than urban populations, and per capita median skyglow eleven times greater). There was significant variation in artificial light at night within different landcover types, emphasizing that light pollution is not a solely urban issue. Further, half of English National Parks have higher levels of skyglow than light emissions, indicating their failure to buffer biodiversity from pressures that artificial lighting poses. The higher per capita emissions in rural than urban areas provide different challenges and opportunities for mitigating the negative human health and environmental impacts of light pollution.
Highlights
Outdoor artificial nighttime lighting, from streetlights and other sources, has increasingly been recognized as a significant anthropogenic pressure on the environment (e.g., [1,2,3])
We found that the indirect effects were stronger than the direct effects, demonstrating that, there was a positive relationship between human density and artificial light at night, there was a stronger effect of people living in close proximity in urban areas producing less light per person
The analyses reported here emphasize the pervasiveness of artificial nighttime light, especially when both light emissions and skyglow are considered
Summary
From streetlights and other sources, has increasingly been recognized as a significant anthropogenic pressure on the environment (e.g., [1,2,3]) The disruption it causes to natural light regimes has a wide range of impacts, in large part because of the central role that these regimes commonly play in determining the timings of biological activity [4]. Key to determining where the biological impacts of artificial nighttime lighting are likely to be experienced, is an understanding of the spatial occurrence and variation in that lighting, and how this changes with other factors [3] To date, from this perspective, this understanding has been rather limited. This focus has been because urban infrastructure is clearly a major contributor to artificial nighttime lighting, and in part because of interest in the potential to use remotely sensed data of such lighting to track or hindcast changes in urbanization and human density, where such information is not directly available
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