ALAN is being increasingly recognised for its impacts on human health, culture and biodiversity (Davies and Smyth, 2017). Marine, freshwater and terrestrial habitats around the world are already being affected, although the extent to which different regions and habitats are impacted is not homogenous.
Twenty-three percent of the world’s land surfaces between 75°N and 60°S have light-polluted skies (Falchi et al., 2016). Between 2012 and 2016, there was a total radiance growth of 1.8% per year with the brightness of continuously lit areas increasing by 2.2% per year (Kyba et al., 2017). There were few places where lighting growth was stable or decreasing in this period and it is expected that artificial light emission will keep increasing. In densely populated industrialised countries there has been a considerable amount of artificial light for decades (Koen et al., 2018). Half of the United States of America and 88% of Europe have light-polluted skies, for example (Falchi et al., 2016).
Singapore is the most light-polluted country as sky brightness is >3000 μcd/m2 for the entire country1 .