Thought about it myself, part of me wants them to be like Bosmer. Bosmer don't eat vegetation - at least those who follow the Greenpact don't. Greenpact is something that is basically very similar to the Green Word that Viera follow in protecting the wood. So, does make it little sense for them to not damage the wood/jungle and nurture it - and that includes not damaging it/eating it. Bosmer are also cannibalistic xD