Stories about how communities thrive in the resource-constrained environments that islands present may provide lessons about sustainability, but those lessons will need to be ported to the mainland if they're to have any significant global impact. Happily, sustainable mainland communities and sustainable island societies may have more in common than is immediately obvious.
When I started focusing on sustainability at Greenback U., my charge was to figure out how to make the campus operate sustainably which, as originally defined, meant with no net emissions of greenhouse gases as estimated by a fairly narrow set of metrics. Emissions caused by burning fuels on campus were considered, as were emissions resulting from Greenback's demand for utilities like electricity. But the only other indirect emissions (those not emanating physically from the campus itself) addressed were the ones created by student and employee commuting, and by university-paid air travel. The need to estimate commuting emissions drew my attention to the behaviors of members of the Greenback community while off campus, and to the impacts of local infrastructure (or the relative lack thereof) on those behaviors. While this, by itself, was enough to convince me that it's unrealistic to conceive of a sustainably-operating institution in an unsustainably-operating community, the profundity of the truth of that statement took many years to sink in.
Research conducted around the world since Greenback signed on to the American College and University Presidents Climate Commitment  has helped me understand (at least qualitatively) how much GHG goes into the atmosphere as a result of Greenback's existence and operation. Most of it doesn't physically emanate from campus. Most of it doesn't physically emanate from Backboro, nor from our county or even our state. Most of it physically emanates from places far away -- places we're not consciously aware of and that most of us will never visit. The majority of greenhouse gas emissions for which Greenback is (directly or indirectly) responsible are those created by the goods, and to a lesser extent the services, for which our operations create demand. Emissions occurring in the creation (resource extraction, refining, manufacturing, transportation, etc.) of the books, paper, buildings, furnishings, electronics, food, branded apparel and other goods consumed because Greenback exists. Some of it -- a good portion of the food, for example -- we could argue would need to be created and consumed regardless, as our students and employees would still live and eat even if Greenback had never existed or if they had never become associated with it. But much of the consumption -- books, paper, electronics, sports-fan-wear, etc. -- is clearly a result of the presence of the university. Nobody buys an overpriced T-shirt identifying themselves as a Greenback fan just because they really need another T-shirt, after all. And even in the case of the food consumed, the fact that our campus feeds so many people in more or less the same location at more or less the same time means that small-batch preparation is out of the question. Which means that small-quantity procurement is impracticable. And that local sourcing of most food items is difficult, at best. Big volumes served means big volumes administered means -- in today's world -- that industrially produced foodstuffs are the rule on campus.
Wrap it all together, and the inevitable conclusion is that if Greenback (or any similar institution, or any similarly-sized community however constituted) is to create no net emissions of greenhouse gases, sourcing of all sorts of products must be considered seriously. And since you can't consider seriously what you can't reliably know, the practical implication is that production -- or, at least, the major part of the production process -- needs to occur near enough to Greenback to be observable, and auditable, and certifiable. Today's intercontinental supply chains and international certification protocols simply can't offer any reasonable degree of assurance in these matters. Assurances that they do offer generally dissolve, under stress testing, into one or another form of magical thinking.
So if Greenback's drive to balance unavoidable GHG emissions against irreducible product demand is to be responsibly managed, our supply lines need to get shorter, and our knowledge about those supply lines (and the processes along them) needs to improve. We have to strive to meet our needs with mostly-local/regional production, as we would were we on an island receiving imported goods only infrequently and expensively. Not complete autarky by any means, but perhaps 80% local production and 20% "imports" overall, with a higher local percentage for the absolute necessities. (More on that, later.)
The global economic system won't reward us for prioritizing local sources significantly. On the other hand, the global economic system embodies the path by which we got into this mess.