Really interesting questions, and, as you say, probably hard to answer.
I suspect that, at least, a small but significant number of people who have been in some degree concerned about ecology, wellbeing of the land, locavore-ism, animal welfare, or even just tending a garden, etc. fairly often were young first-time readers of LOTR in the 1950s-1970s. (This was also the time of paperback editions of E. F. Schumacher's
Small Is Beautiful, etc.) Right now all we have, so far as I know, is anecdotal evidence.
The question was, "Is Tolkien Still Relevant?" I have my doubts about whether people, especially the young, who known Tolkien primarily through the movies, are stirred to concerns for the land from having watched them.So, if one refines the question to read, "Is Tolkien still relevant as an inspiration to concern for nature and the land?", I doubt that he is, much.
Tolkien will always be relevant for some readers, in the sense not only of providing superlative entertainment but in that of influencing their appropriation of perennial values. However, the perennial nature of the values that one encounters in Tolkien will probably make Tolkien's work increasingly off-putting to many, as culture becomes increasingly antagonistic towards those values. The more comfortable you are with the directions culture is going, the less taste you probably will have for Tolkien. However, that suggests that, conversely, his books could come to have an "underground" importance for some.
http://touchstonemag.com/archives/article.php?id=15-01-048-f