LOL Something more intellectual and taxonomical than "hippie" or "tree hugger."
I might have said "Naturist," but that has a different meaning, as you will find if you look it up.
King -- better; and Pagan might work, but Paganism tends to be associated also with magical charms rather than a sublime awe of Mother Nature....
dreaming- Gaian is good, but I'm trying to relate it to Wordsworth, and I think the term would be anachronistic, applied to him; but if he were asked, he might go for it.

Josh-- pantheism would be good if you assume that Nature is all there is to reality. Thank you.