I remember the thrill of reading Robinson Crusoe for the first time. Later readings may have surfaced infamous bits of wordplay and troubling social/racial stereotyping, but when I was ten or eleven the image of a lone individual not just surviving but (to an extent) thriving in a wilderness was captivating. No need for a never-ending set of interlocking puzzles as per Lost, no man/beasts created by Dr. Moreau, not even an almost-magical black stallion -- the (by current Hollywood standards) embarrassingly simple story of adversity and unfamiliarity overcome grabbed my childhood imagination and held it for years.
Situating a story on an island has a number of arguable advantages. It plausibly limits the cast of characters -- not necessarily to one, as per much of Crusoe, but to any number the author chooses. And whatever the challenge to be overcome, an island setting can rule out a whole set of established (thus, uninteresting) solutions. In practical terms, any story set on an island is one in which constraints -- obvious physical limitations on who and what can be part of the solution -- are both critical and acceptable.
If stories and story-telling are to be effective in teaching concepts of sustainability, the presence of constraints is probably key. Most of the writing on how to teach sustainability shies away from the concept of constraint, and some authors explicitly warn against using the term out of fear that students will envision any existence in the presence of constraints as undesirable, shabby, nasty, brutish and short. To my mind, however, the implicit assumption that the good life requires ready access to virtually limitless resources is precisely what sustainability stories need to confront. Modern consumerism -- the increasingly dominant social narrative which is consistently reinforced by all sorts of commercial entertainment -- revolves around the untruth that having more stuff, better stuff, often unimaginable stuff, is the one and only path to fulfillment and success. One key message of sustainability is that not only are possessions -- unfettered access to and unlimited utilization of resources -- not the only path to happiness, they're not even a path to happiness. Once a certain basic level of creature comfort is attained, additional possessions are as likely to lead to distress as to euphoria. Perhaps, more likely.
To my mind, then, one defining aspect of sustainability-teaching stories is that the proponents thrive in the presence of relatively non-negotiable constraints. They must attain satisfaction and comfort and fulfillment even though water, or food, or technology, or knowledge, or infrastructure, or whatever is available only in limited quantities. I say "they" because all but the simplest sustainability stories (those appropriate for ten-year-olds, perhaps) will likely feature ensemble casts -- numerous characters who interact as the setting dictates and cooperate to attain (or, if the story is a tragedy, fail to attain) sufficiency and satisfaction.
Perhaps invention and cooperation in order to thrive in a constrained environment will, itself, be the heart of some stories. In other cases, the story may be set in a (micro-)society where inventive cooperation is already an established norm. The proponents will look like you and me -- not Bruce Wayne, nor Lara Croft, nor Jason Bourne. Their adversaries, if human adversaries are featured, will also seem familiar. And magic (or technology sufficiently advanced as to be indistinguishable from magic) won't be present.
After all, that's how life works. And how society works. And how each of them will have to be sustained. (Unless, of course, we're all operating inside a tragedy.)