I'm used to seeing luxuriant moss in the forest but this is a different environment. Everywhere I look in the city I see moss. Some species of moss have adapted very well to city living. We've provided nooks and crannies, built our homes, pathways, headstones and factories out of granite, sandstone and limestone so the mosses feel quite at home. It amazes me to see moss growing on busy pathways, carparks, steps and walls, keeping its head down. So small that even when it sends up its sporophytes its barely noticeable. It amazes me that it can survive for long periods of heat and drought in such hostile environments and then flourish after the first rain.
I've read that moss it very susceptible to pollution so perhaps we should feel reassured as long as the moss is happy to be there – a bit like taking a canary down a mine to test the air. When I was a child we played the game of stepping over the cracks in a footpath because to step on one was bad luck. Bad luck for the moss maybe, but I never thought of that at the time.