From what I have gathered regarding sustainability, which relates well to wahn's blog on overpopulation, is IPAT: environmental impact = population * affluence * technology.
Here are possible solutions, all of which are required to have a sustainable society:
- Type III ecology via industrial ecology (technology)
- Biomemetics (technology)
- Steady-state economy (affluence)
- Limiting population growth (population)
Anyway, the first two points regard efficiency of humaniy's synthetic systems and technology, and the latter two are about growth. In a system where you have no introduced energy/matter and no losses of energy or matter, you have an isolated system.
For interest's sake, here are some interesting quotes from a fairly revolutionary journal article from 1971:
"Racism, economic exploitation, and war will not be eliminated by population control (of course, they are unlikely to be eliminated with out it).
"Moving people to more "habitable" areas, such as the central valley of California, or indeed, most suburbs, exacerbates another serious problem -- the paving-over of prime farmland. This is already so serious in California that, if current trends continue, about 50 percent of the best acreage in the nation's leading agricultural state will be destroyed by the year 2020.
"Theorem 5 states that theoretical solutions to our problems are often not operational, and sometimes are not solutions. In terms of the problem of feeding the world, for example, technological fixes suffer from limitations in scale, lead time, and cost."
http://faculty.washington.edu/stevehar/Ehrlich.pdfhttp://www.jstor.org/pss/1294858 --
working on getting full article. Will give article on individual basis.