I've never added voice to my own work, but I know the feeling of wanting to say more than the frame holds. What are you hoping the voice would do that the land itself isn't already doing?

Caption holds more than voiceover for this kind of work. A voice layered over landscape footage often competes with the image instead of serving it, and once you add a CTA the whole thing starts reading like an ad rather than a piece. Let the video breathe and put your context where people can return to it.