Everything from our sleep to our hormones relies on the dark. So why are we so intent on destroying it?

Humans have always feared the night – and now we are wiping it out, one streetlight at a time. That’s terrible news for our bodies and minds – and the rest of nature

The clocks have changed for winter and night falls early. I’m in a small wood near my house in west Wales. My hands and feet tingle with cold. I can hear the stream rushing, a rustle in the wet leaves. There was a full moon at the weekend, so the nights are bright. Under the trees there’s a smudge of faint bluish light, a slide of shadow. This has its own magic, but I’m looking for the dark.

I like walking with the dark and I’m fortunate to live in a place where it’s safe to do this. I’m also lucky because real darkness still exists in parts of Wales. Urban areas in particular can be stripped of the dark. London, which is awash with unnecessary illumination, is 24 times brighter than dark areas of south-west England, according to a London Assembly report. Light corridors from trunk roads and motorways are clearly visible from satellites. But on a moonless night, walking in these woods – a long way from streetlights and houses – the familiar paths, trees and contours are all hidden. If I hold out my hand, I can’t see it. I only know my feet are there because I can feel the tug of my wellies.