Fungi are the hidden kingdom, the decomposers, the recyclers. They live in the dark, breaking down wood and leaves and dead things, turning death into life. But some fungi have a secret. They glow. Bioluminescence – a green, eerie, otherworldly light that pulses from their gills on dark nights. Walk through a forest and see a fallen log lit up like a lantern, and you will never forget it. There was once a fungus that glowed on the coasts of New Zealand – brighter, larger, more spectacular than any alive today. It was the coastal glow ghost, and it is gone. Its light made it special. Bioluminescence is rare among fungi – only a handful of species produce it. The lost coastal fungus was one of the brightest. Its green glow could be seen from metres away, illuminating the driftwood piles and decaying logs of the shoreline. It was a beacon in the dark, a ghost light that guided night-time wanderers. Scientists are not entirely sure why fungi glow. Some think it attracts insects, which then spread the fungus's spores. Others think it deters predators. Whatever the reason, the glow of Omphalotus littoralis would have been a spectacle – a living lantern on the shore. It decomposed. Fungi are the great recyclers of the forest. They break down dead wood, releasing nutrients back into the soil. The coastal glow ghost specialised in coastal wood – driftwood, fallen branches, the rotting stumps of pōhutukawa and coastal flax. It was part of the shore's cleaning crew, turning dead trees into living soil. Its spores were dispersed by wind and perhaps by insects attracted to its glow. It grew in clusters, often covering entire logs with its orange-brown caps and glowing gills. Fungi reproduce by spores, millions of them, released from the gills beneath the cap. The spores are tiny, carried by the wind. When they land on suitable wood, they germinate, sending out thread-like hyphae that penetrate the dead tissue. The fungus spreads, slowly consuming the log from the inside. That strategy works when the logs are abundant. It fails when the logs are removed. Coastal logging and driftwood clearance destroyed it. When Europeans arrived, they logged the coastal forests for timber. The pōhutukawa, the coastal flax, the scrubby hardwoods – all were cut down. The logs that remained were often burned or removed from beaches. At the same time, beachgoers cleared driftwood for campfires and beach fires. The dead wood that the fungus depended on disappeared. Without logs to grow on, the fungus could not survive. Introduced fungi may have delivered the final blow. Competing fungi – introduced species that arrived in soil, on timber, or in the ballast of ships – outcompeted the native glow ghost for the remaining wood. By the 1920s, it was gone. The last specimens were probably collected by a naturalist who had no idea he was holding the final individual. He pressed them, dried them, put them in a drawer. And the coast fell dark. The Australian jack-o'-lantern mushroom still glows in forests across the Tasman. But New Zealand's coastal glow ghost is extinct – a light that no longer shines, a ghost that no longer haunts the shore. We cleared its logs. Then we wondered why the coast felt so dark.