I wouldn’t exactly call these birches a forest, and “wood”, or “copse” or “grove” or “thicket” are also plain wrong. Even the Icelandic, “skogur”, can’t be right, because it applies to any kind of group of trees at all, and, well, these are very special. They’re more like people.
“Community” seems rather generalized, and “congregation” is too churchy. What about “band”? That’s more like a line, isn’t it, and not this spreading out and appearing. We could say it is a “bosk,” though. That’s an old word for a kind of thicket, with the old proto-Indoeuropean sense of “appearing.”
Any celt would have been happy with that, and there’s a lot of celtic memory in Iceland. The French are happy with it, too, and would just call this a “bois.” A gathering together, and what is a gather but a clump, or a thickening, that is held by an external force, in this case, the cliffs of Ásbyrgi.
Look how they are alive with this sense of “peopling” as well: a busk, or bois, or gather of stone. There is an energy leading all these forms to come together in this pattern, and it is this energy that is Iceland. Just ask a puffin.