A patch of moss is doing more for the life around it than it looks. It is food, shelter, building material and a damp refuge all at once, and the garden is poorer without it.
Birds build with it
Many birds line their nests with moss, prized for being soft, insulating and good at holding a little warmth. Wrens, robins, chaffinches, long-tailed tits and others gather it every spring, working it into cups and domes alongside grass, hair and spider silk. A garden with moss to hand makes that work easier, which is one good reason not to scour every last scrap off the lawn and walls in March, just when the birds most want it. Long-tailed tits build especially elaborate mossy nests bound together with cobweb, and a bare, over-tidy plot gives them very little to start with.
A world for invertebrates
The damp, sheltered spaces between the leaves and stems hold springtails, mites, beetles, spiders and a host of smaller creatures, and the things that eat them come looking. Moss is hunting ground as much as habitat. A single cushion can carry a dense population of tardigrades, the water bears that ride out drought curled up dry and revive when the rain returns, along with rotifers and nematodes living in the film of water around each leaf. All of this goes on unseen in a scrap of green most people would step over without a glance. For the truly tiny end of that community, see the hidden world in a moss cushion.
A refuge when it is dry
Because moss buffers humidity and temperature, it gives small animals somewhere to ride out a dry, hot spell that would see them off on bare ground. Under a mossy log or against a shaded wall base the air stays cooler and damper than a few inches away in the open, and creatures that would dry out in the sun shelter there through the worst of the day. Amphibians such as frogs and toads use damp, mossy ground in the same way, resting up in the cool while they wait for the evening to move. In a warming climate that buffering matters more, not less. A mossy log, wall base or shady corner is a little reservoir of cool and damp that the rest of the garden can draw on.
Part of a healthy garden, not a disease
It helps to see moss as one thread in the garden's web rather than a blemish to be scrubbed away. It is not a sign of disease or neglect, and it does not smother healthy plants or poison the soil under them. Where it grows it feeds and shelters small life that in turn feeds the frogs, toads, hedgehogs and birds many gardeners are glad to see. Ground that grows moss is usually just shaded and damp, and those are exactly the conditions a great deal of wildlife prefers. Treating every patch as a fault to be corrected takes shelter away from the very creatures a garden is meant to hold.
Leaning into it
You do not have to do much: leave some moss rather than removing all of it, keep a shady damp corner, and resist the urge for a sterile, scrubbed surface everywhere. Let a log rot quietly, allow moss to gather on the north side of a wall, and think twice before treating a lawn with iron sulphate that will blacken every cushion the invertebrates depend on. A garden that tolerates moss supports more life, with no extra work. See what moss is good for for the wider picture.