The 2015 National Book Award Nonfiction Longlist contains two books classifiable as natural history: Rain: A Natural and Cultural History by Cynthia Barnett and The Soul of an Octopus; A Surprising Exploration into the Wonder of Consciousness by Sy Montgomery.
Curiously, neither of these books was on my radar as no review copies ever arrived. Thus I am uncertain as to which I would prefer to see ultimately chosen as the winner.