Light can be bad for you

Standing on a Lake District hillside on a clear night, it is still possible to see the Milky Way. The fells are dark, the bracken has died back, and the land feels momentarily timeless. Somewhere down the valley a farmhouse light glows, while Ambleside shines with confidence. Even here, darkness is no longer what it once was. Light creeps along valleys, clings to roads, leaks from farm buildings, and follows visitors who arrive convinced that night is something to be conquered rather than experienced. 

In this episode of The Bit Outside, I reflect on artificial light at night. Not poetic light, or spiritual light, but the everyday glow from bulbs, switches, security lamps, car parks, head torches, campsite lighting, and our collective discomfort with the dark. Used badly, light is not merely irritating. It alters ecosystems, disrupts sleep, and may even make us ill. 

Light pollution does not arrive as one dramatic event. It arrives quietly, in often well-intentioned pieces. A security light left on because someone once heard a noise decades ago. A brighter campsite for convenience. A car park upgrade. A council decision made by someone who has never watched a bat follow a dry-stone wall at dusk. Each light seems trivial. Together, they change the night. 

Insects are among the hardest hit. Above the bracken, moths, beetles, midges and crane flies move constantly. Artificial light draws some in, pushes others away, exhausts many, and makes them easy prey. A single bright light can pull moths away from feeding and breeding grounds. Lines of road lighting can split insect populations from one side of a valley to the other. When insects decline, every living creature above them in the food chain is affected, including us. 

Bats, too, are affected. Many species commute along walls, hedges and streams, sometimes covering surprisingly long distances each night. Turn on a light in the wrong place and the route breaks. Some bats will not cross illuminated gaps at all. Others detour, lengthen their journeys, or give up feeding opportunities altogether. There is no sudden disappearance, just a quiet reduction in efficiency. Nature rarely collapses with a bang. It frays. 

Trees respond to light as well. Artificial illumination can trigger earlier budburst and delayed leaf fall. Leaves stay longer. Buds open sooner. That sounds harmless until frost arrives early, fungi miss their timing, or insects find leaves tougher and less palatable. Small shifts ripple outward. In nature, timing is everything. 

Even water notices light. Tiny drifting animals rise towards the surface at night to feed and sink by day to avoid predators. Artificial light flattens that rhythm. Predators feed for longer. Algae behave differently. In upland pools the effect may be subtle, but further down the valley it grows. 

Birds sing earlier near lights. Artificial dawn arrives before the real dawn. Breeding timing nudges forward. Again, this is not catastrophe. It is pressure. Artificial light is now recognised as a genuine environmental driver. It spreads quickly, affects many species, and differs from most pollutants in one crucial respect. It can be switched off.

Humans are not exempt. Our biology is organised around light and dark. Melatonin rises in darkness. Light suppresses it. Even low levels of night-time light disrupt sleep, interfere with metabolism, affect mood, and may contribute to longer-term health risks. This is not fringe science. It is mainstream. 

Light is a strange pollutant. Essential, helpful, and yet harmful when misused. Unlike many environmental problems, it can be reduced immediately, quietly, and locally. 

This episode is not a call for panic or purism. It is a reflection on how easily we have lost the night, and how gently we might reclaim it. 

If you can, turn off that light. Not tomorrow. Not later. Now.