Sustainability is how we go about "having a future"

The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there’s no good reason to go into space–each discovered, studied, and remembered by the ones who made the irrational decision. (Randall Munroe)

Well, I don't claim to know the rest of the universe well enough to make such a strong statement as that "probably" there. But then perhaps I don't quite have the kind of enquiring mind to which such statements come so easily.

My comparatively insular mind, for what it's worth, can at least conceive that it's possible that the universe is instead littered with the one-planet graves of cultures who instead made the bold, dashing, romantic, exploratory decision; that in the face of such potential excitement, there was no good reason to preserve their own ecosystem, especially when there's probably so many other potential ecosystems out there; each of those graves in turn discovered, studied, and remembered by the others: the ones who worked out how to live sustainably, before trying to live beyond their means.