I'm more and more convinced that assessing/accounting for environmental sustainability only makes sense at a regional scale. While "region" isn't precisely defined, it's something smaller than most nations, smaller than most US states (except maybe on the eastern seaboard), larger than a city, certainly larger than any campus. But sustainability extends beyond its environmental aspect, and for other (social, economic) forms of sustainability, the regional scale is even more critical. Certainly, it seems so in a US context.
Social sustainability, in a nutshell, is all about the robustness (more or less) of the ties that bind the social system together. Are they sufficient to survive current stress levels? Impending stress levels? The highest foreseeable stress levels?
A number of sustainability folk -- at least, a number of those who concern themselves with social sustainability at all -- consider "social sustainability" to be equivalent to "social justice", meaning equity, ultimate fairness, some form of Deweyan democracy. I'm more sanguine, in that I'm willing to acknowledge that some of the most stable societies the world has yet seen -- ancient Rome, China for centuries -- have been anything but democratic. I can argue that, in theory, any society which depends for its continuance on the successful repression of most of its members is inherently unstable. On the other hand, it's hard to ignore the evidence of so much history.
But it's even harder to imagine how to achieve social sustainability on anything larger than a regional scale. Anyone who's lived in a number of locations in the USA can attest that we're not a single culture or a single society, we're multiple cultures -- almost multiple nations -- within a single country. Different values take precedence in different geographic regions -- not usually because of the geography per se (although that can be a factor), but largely for historical and cultural reasons. Folks move south, or west, or north and find themselves operating in a milieu different from what's familiar to them. They learn. They adapt. Within a decade (often less), they may espouse values they never previously held. Culture can have that effect.
So when we talk about a culture's sustainability, its resilience, we're not talking about the same thing in Dallas as we are in Detroit. Atlanta isn't the same as Anaheim, nor Amherst, nor Altoona. Some American cultures are resilient, while others are not. And which is which can vary over time.
As regards economic sustainability, the importance of regions is even more clear. The US national economy is an accounting fiction; it's more meaningful to speak of it as a subset of the global economy or as a collection of regional economies. For purposes of sustainability (since, in the long term, any global economic system has too many potential points of failure to be resilient), it's the regional scale that makes the difference. Are people interacting sufficiently -- meeting each other's material needs, providing each other with gainful employment -- within a particular area of the country?
Given the huge variability that exists within the USA, it's evident that social and economic sustainability can't be achieved on a national scale. The necessary span, the tremendous scope of effect, of any control decision would simply be too great. The information required to justify a control decision -- certainly, if that decision is to be made by a governmental, or even a corporate, entity -- is too massive. And given regional differences, the idea that a national-level decision -- a one-size-fits-all balancing move -- could ever work is simply ludicrous.
Sustainability, whether it's environmental, social or economic, can only hope to be achieved at a regional level, give or take. If we're going to study it, we've got to study what's happening in our own regions. If we're going to model it, scoping our models to fit relatively homogenous regions will be necessary to make the effort at all possible. If we're going to teach it, basing our teaching on what can be demonstrated or observed within spitting distance of campus has tremendous advantages. (But more on that, later.)