Skyglow extends into the world's Key Biodiversity Areas

The proportion of the Earth's surface that experiences a naturally dark environment at night is rapidly declining with the introduction of artificial light. Biological impacts of this change have been documented from genes to ecosystems, and for a wide diversity of environments and organisms. The likely severity of these impacts depends heavily on the relationship between the distribution of artificial night-time lighting and biodiversity. Here, we carry out a global assessment of the overlap between areas of conservation priority and the most recent atlas of artificial skyglow. We show that of the world's Key Biodiversity Areas (KBAs), less than a third have completely pristine night-time skies, about a half lie entirely under artificially bright skies and only about a fifth contain no area in which night-time skies are not polluted to the zenith. The extent of light pollution of KBAs varies by region, affecting the greatest proportion of KBAs in Europe and the Middle East. Statistical modelling revealed associations between light pollution within KBAs and associated levels of both gross domestic product and human population density. This suggests that these patterns will worsen with continued economic development and growth in the human population.