While the hit sequel about wayward zoo animals is played for laughs by its cast of comedians (Chris Rock, Ben Stiller, David Schwimmer and Sacha Baron Cohen), there’s a minor environmental plot thread with a potentially serious outcome: stranded tourists selfishly dam a river, diverting the water supply and threatening the idyllic ancestral watering hole. The zoo crew saves the day, of course, but not before the movie makes a valid point about preserving nature.