Beyond this barrier is the concept of resources - resource sharing, distribution, pooling, management. Herein, I find territorialism's weakness - by limiting a resource base, inequalities and disparities between neighboring communities are inherently made more obvious. Territorialism might be nice for communities trying to preserve tradition, but it can not work to bring disparate communities together.
My thoughts keep returning to Long Island City and the transformations I saw underway there. There is such a huge difference between the rent/apartment prices in the new buildings popping up along the river and the rest of (/former residential) LIC, breeding new demographic shifts. Over the two years I lived there, I saw the two small commercial areas becoming more and more distinct from each other - and holding very specific segments of the small area. The new towers claim 'sustainability' while bringing luxury to (part of) the area, creating new social boundaries. The rent of the new buildings has to be inflated to balance the greater initial investments by 'green market' seeking developers. Incoming residents of these towers do not join those living in their shadows shopping at the budget C-Town grocery, even though the 4 or 6 block walk is convenient.
Many people overlook or seem to forget it, but sustainability has a social component, a component of equity which seems to fight with economics. It's great if the costly solar panels on a new building contribute to its electricity usage, but what about the neighbors - the existing communities - who might be forced to move and dissipate in order to continue to afford their meager existence living on the grid?