You may not think about coastal mosses. They are the tough ones, the dark ones, the ones that grow where the salt spray flies and the waves crash. They are the living carpets on the grey rock, the green blankets on the stone. And there was once a coastal moss that grew thicker than any alive today – a moss whose stems rose 8 centimetres from the rock, whose leaves were dark and dense, whose mats were so thick that you could press your hand into them and feel the spring. It was the giant rocky beach moss, the stone ghost, and it is gone. What made it special? Its thickness and its toughness. An 8-centimetre moss on the exposed coast is a giant – a dense, springy mat that covered the rocks, holding moisture, absorbing the shock of the waves, providing shelter for the small creatures of the splash zone. Its leaves were dark green to almost black, thick and leathery, able to withstand the salt spray and the pounding sun. What did it do? It held the coast together. On the exposed rocky shore, the moss was the first line of defence. Its dense mats trapped moisture, preventing the rock from drying out. Its roots held the thin layer of soil, preventing erosion. It was the engineer of the coastal rock garden, the plant that made it possible for other plants to grow. Its mats provided shelter for tiny crustaceans, insects, and mites. Its leaves held moisture through the dry spells, releasing it slowly back into the environment. It was the heart of the coastal rock community. Breeding? Mosses reproduce by spores, released from capsules on slender stalks. The giant rocky beach moss produced spores in dark, urn-shaped capsules that rose above the mat. It grew slowly – a few millimetres per year – and an 8-centimetre mat might be decades old. That strategy works when the coast is stable. It fails when the rocks are moved and the coasts are developed. Why did it vanish? Coastal development and rock collection. When Europeans arrived, they developed the coasts for housing, harbours, and roads. They built seawalls, laid paths, cleared rocks for gardens. The giant rocky beach moss, which grew only on specific rocks in specific locations, lost its home. At the same time, people collected rocks for garden walls and ornamental features. The moss came with the rocks – or was scraped off and discarded. A single rock collector could destroy decades of growth in a single afternoon. By the 1910s, it was gone. The last patches were probably destroyed by a road builder or a rock collector. No one knew they were the last. The smaller coastal mosses survived. They are lower-growing, more adaptable, able to grow in a wider range of conditions. They are the survivors, the ones that kept their heads down. But the giant rocky beach moss is extinct. A few pressed specimens in a herbarium, a few fragments of its DNA, and the memory of a moss that used to cover the coastal rocks, a stone ghost on the stone. The stone ghost has crumbled. The rocks are not as green as they used to be.