There are likely no effectively isolated communities left. This is mostly due to technology informed by science (a form of common knowledge), and the dominant value system's stated goal of subduing the Earth, which has been very successful. To the extent that the resources that drive that technology are becoming more scarce, our global community will become less viable. Anticipating that, the Transition movement is getting (barely) ahead of the curve, so-to-speak, and attempting to create smaller communities that can thrive on local resources, making the inevitable disintegration more controlled and, as a result, less painful.
Contrary to the view of conspiracy theorists on the “right” side of the political spectrum (in the U.S.), those who identify themselves as environmentalists are not driving this transition in the pursuit of power. They are trying to confront perhaps the greatest existential threat to humanity, caused by the systematic plundering of the biosphere which the dominant value system promotes, and avoidance of basic knowledge about the world exacerbates by keeping people ignorant of its consequences. This clearly significant problem with the quality and pervasiveness of our community knowledge and values needs to be fixed, even if we do splinter into smaller groups, because those groups will likely still need to interact, if for no other reason than to share and help develop resources critical to survival.
As smaller communities become more viable, their common knowledge and values will likely evolve to adapt to their local conditions. Ideally, they will maintain, intact, parts that enable them to contribute to a healthy planet (and keep from harming other such communities).