Yudkowsky flirts with tautology in the title - "well-kept garden" has keep right there explicitly and "garden" implies a caretaker. So almost by definition a well-kept garden won't persist without intervention.

But also of course not all ecosystems are gardens; not all ecosystems rely on keepers who are external to the ecosystem. A normal forest is sustained by natural forces and the normal actions of its inhabitants. As much as possible I'd like a community that sustains itself rather than one that is gardened.