The ideal of sustainability can’t be seen as a static goal, which represents the end of our efforts, once reached.

In practice, all complex systems need to constantly adjust their parameters to support themselves in their changing environment.

And in the process, their components will change, and evolve. If from the point of view of the system as a whole we can observe this continuity, it is only possible through considerable effort and adaptation.

From the point of you of the component parts that are replaced, there is no continuity, no sustainability.