Life Where Plants “Shouldn’t” Be
Walk across a hot geothermal field, an urban sidewalk, or the edge of Antarctic ice, and you may be stepping past one of the hardiest forms of plant life on Earth: moss. These tiny plants have colonized habitats that defeat most vascular plants.
Masters of Desiccation and Heat
In arid and semi-arid regions, many mosses withstand months of near-complete dryness. Species such as Syntrichia caninervis collect moisture not just from rain but from dew, fog, and condensation in the air.
Other mosses grow on substrates heated by geothermal activity, enduring temperatures above 50°C. Their small size and simple structure, along with the ability to dry out and revive within hours, allow them to ride out extremes that would cook or desiccate most vegetation.
Urban Cracks and Freshwater Worlds
Mosses don’t shy away from human-built environments. They colonize cracks between paving stones, roofs, walls, and disturbed soils—places where heat, drought, and disturbance are common.
Some species specialize: Bryum argenteum is famed as the cosmopolitan sidewalk moss, while Ceratodon purpureus, the red roof moss, thrives on exposed urban surfaces. Others live fully aquatic lives in clean, slow-moving waters, like Fontinalis antipyretica, or build dense, spongy carpets in bogs as Sphagnum does.
Even fully aquatic species, however, must time reproduction to when capsules can emerge into the air, either by elongating their stalks or waiting for water levels to drop.
The Mystery of Glacier Mice
On certain glaciers, researchers have discovered strange, oval bundles of moss slowly rolling across the ice. Nicknamed “glacier mice,” these mobile colonies form when moss establishes on a small impurity and then grows into a compact cushion.
Wind and meltwater nudge the bundle along, keeping its underside insulated from freezing and perhaps allowing it to gather fine sediments and nutrients. Despite living on ice, glacier mice never appear on vast, featureless ice sheets—hinting that they still depend on some exposed non-ice substrate during their formation.
Pushing the Edge of Possibility
Mosses challenge our idea of where plants can live. Desert crusts, boiling ground, city gutters, subpolar lakes, and moving ice all host these survivors.
Their presence in such extremes doesn’t just showcase resilience—it hints that wherever a bit of water, rock, and light coexist, life will attempt to gain a foothold, one tiny green filament at a time.