By definition, all previous ecosystem and non-human collapses were not 'understood as collapse' by those organisms alive during the collapse. Similarly, during historical human social collapses, (Rome, Easter Island, Anasazi, Maya, etc.), people might have known they were in the middle of some unpleasant trajectory, but they didn't have the knowledge, historical record, technology or communication that modern society possesses in understanding/explaining what was transpiring. As such, when this civilization 'collapses', (which in the opinion of this writer is inevitable - the timing, direction, and severity of which remain the salient unknowns), it will be the first to have at least some portion of its inhabitants anticipate and understand its own collapse in a systems dynamics sense. How will this odd 'collapse trivia' manifest in steering/pulling/resisting actual collapse, if at all?
That's worth pondering, but unlike Hagens, I don't see the collapse of all civilization as "inevitable." Too End-Times-ey for my taste.