Try To Tap Into Universal Themes.
You know what made Star Trek IV: The Voyage Home a big hit? It was about something more than just the traditional science fiction themes, and so more people found themselves interested (Well, that and the sight of Leonard Nimoy with a sweatband around his head. I mean, come on). So why not tackle something meaty like the ecology? Admittedly, a cannibal plant might be a little too on the nose, but still.
Metaphor Is Your Friend.
One of the best things about the original Trek television show was the way in which it was unafraid to deal with contemporary topics through (admittedly, increasingly tenuous) metaphorical means. Yes, I have no desire to read about merpeople in space, but that line about “All your people once were air-breathers! And these children — How can you destroy your own children?” makes me think about the inherent possibility for accidental child death in any armed conflict and, now, I’m interested. See?!?
More On Techland: Plinkett Defends Movie Remakes With the (Old) New Star Trek Movie