There are no separate systems. The world is a continuum. Where to draw a boundary around a system depends on the purpose of the discussion.

Eleventh Commandment: Thou shalt not distort, delay, or sequester information

Any system, biological, economic, or social, that gets so encrusted that it cannot self-evolve, a system that systematically scorns experimentation and wipes out the raw material of innovation, is doomed over the long term on this highly variable planet.

We don't think a sustainable society need be stagnant, boring, uniform, or rigid. It need not be, and probably could not be, centrally controlled or authoritarian. It could be a world that has the time, the resources, and the will to correct its mistakes, to innovate, to preserve the fertility of its planetary ecosystems. It could focus on mindfully increasing quality of life rather than on mindlessly expanding material consumption and the physical capital stock.

Since the Earth is finite, and we will have to stop expanding sometime, should we do it before or after nature's diversity is gone?

You should issue demerits for tree cutting or the destruction of humus.

A good leader sets the right goals, gets things moving, and helps us to discover that we already know what to do.