But I don't think either novel has been especially popular among the green left and LeGuin and Robinson aren't especially tied in.

I named those works specifically because they are mentioned in this paper (only abstract is free access):

Green utopias: beyond apocalypse, progress, and pastoral

From the abstract:

This article focuses on these utopian attempts to find routes out of the ecological crisis and map the possibilities of better, greener futures. I begin by arguing that whilst utopian theory has begun to consider the content of ecological future visions, there has been little attention to the ways in which the reflexive and critical strategies of recent utopian narratives can make a distinctive contribution to radical ecology's social critiques and the process of imagining more environmentally cautious forms of society. I therefore look in detail at two examples of green utopian fiction to analyse how they address the question of how humans can live better with nonhuman nature in the context of contemporary Western debates about the environment. They are Ursula K. Le Guin's Always Coming Home and Kim Stanley Robinson's Pacific Edge.

(Emphasis added.)