Enviro22:
Great questions, as I am in a similar dilemma about Ecology vs Natural Resources vs Human Dimensions (including Interp). My background is mostly interp and enviro ed, but I am looking to take it to a higher level of science knowledge and education. Hopefully moving away from children's ed.
Anyway, just wanted to respond because my sister is doing her PhD at CSU under Warner College. She's in watershed and geosciences I think, but has encouraged me to look at their HDNR program as she knows some people in that program and it sounds like a great match for a person who wants the sciences, but people part too. It is still a fairly new program, but that could offer more flexibility in creating your own area of interest. In fact, some of the phD students in that program area were part of an interdisciplinary team that my sister was on doing research in Mongolia last year. Cool stuff! Quote from the advisor when my sister connected me to her and I told her my background "with your background in art/humanities and field experience in environmental education – our program could offer more diverse natural resource training and well as tools to move into career-level environmental ed – either for adults or children." The department offers more than just EE though, so well worth looking into. Plus that school and Ft. Collins are just great places to be.
I am waiting to hear from a grad student and an advisor in that department just for general conversation. I'll post more if I get to talk to them. If you like interp studies, you might want to check out SUNY's Enviro Interp Masters: http://www.esf.edu/efb/envint/
Good luck, hope that helps!