Comparing future histories has led us back to (what I call) Poul Anderson's Directorate History, which is just four stories.
"The Faun" was published in Boy's Life and thus is one of Anderson's juvenile works (see also here). The title and the opening sentence:
"A wyvern flew up in a thunder of splendid wings."
-Poul Anderson, "The Faun" IN Anderson, The Queen Of Air And Darkness and other stories (London, 1977), pp. 86-90 AT p. 86 -
- suggest a fantasy but the following sentences clarify that the story is set on a colonized extra-solar planet.
"A python tree coiled its branches." (ibid.)
A tree so called because its branches move.
"A chiming rang among the tiny red blossoms that covered the ground." (ibid.)
As often before, Anderson tells us what a terrestroid planet has instead of grass.
"Alien in the forest, a grove of pines stirred only to a breeze." (ibid.)
this planet has been colonized by human beings who have brought some of
their own ecology with them. And that concludes the opening paragraph.