I particuarly enjoyed the short story at the end of this week's Nature, called "Without", by Fran Wilde (http://www.nature.com/nature/journal/v489/n7416/full/489466a.html). I found another story she'd written, "Everybody loves a hero" (http://dailysciencefiction.com/science-fiction/superhero/fran-wilde/everyone-loves-a-hero), and also discovered the site "Daily Science Fiction".
With just a little exploring, I found two stories that could be effective ways to start discussions in a biology course.
"A concert of flowers" features a 'doctor of alien botany', and addresses questions of conservation and the value of species (http://dailysciencefiction.com/science-fiction/biotech/kate-o-connor/a-concert-of-flowers).
"Sweet as peaches" looks at a world that struggles to sustain the human population, so children grow up never knowing peaches (http://dailysciencefiction.com/science-fiction/biotech/shane-d-rhinewald/sweet-as-peaches).
The story in Nature, Without, is also in the 'collapsed ecosystem' genre, which I find particularly effective as teaching tools. Yes, it's sci fi, but how sure are we that it isn't where we're headed?
I should also share a link (but not necessarily an endorsement) to "Silent Running", the 1972 film set "in a future where all flora is extinct on Earth. An astronaut is given orders to destroy the last of Earth's plant life being kept in a greenhouse on board a spacecraft" (http://www.imdb.com/title/tt0067756/).
Via Mary Williams