Only shine the light where and when it is needed – the impact of light pollution

There is growing evidence that artificial light at night (ALAN) has an adverse effect on human health and ecology. Long-term global studies also show that the world is getting brighter at night. This technological advancement comes at a price to both humans and nocturnal species that share our planet. Light pollution is wasted energy when the world is in simultaneous climate, biodiversity and energy security crises. There are no known negative consequences of reducing light pollution. A vital next step is to make 'quick win' changes by following the basic principles of using light only where it is needed, in the right amount, in the right place, at the right time and with the right colour. We advocate for more research into the adverse effects of ALAN on human health to help drive these changes and allow people to make informed choices about how light is used at local, national and international levels.