When cliff faces are too cold, lichen can do just fine by growing in a tension with heat conserving mosses.
But tufts of arctic grass gnawed to mounds by sheep work just as well. Look how purslane, grass, moss and lichens all work together to create a balanced environment, conserving heat, gathering rain, relatively impervious to sheep, and even collecting soil ot of the wind. Clumps like these, and there are billions of them in Iceland, are like reefs on a continental shelf, or miniature planets in the cold of space. The missing co-conspirators? Ah…