Designer Ecology

[Moontanman]

Is it possible to design an ecology from the "ground up"? How complex should it be? How large would the enclosed space have to be? I rather like the idea of a space colony shaped like a toriod. Spinning to make artificial gravity on it's inner surface. The first questions to be answered would be how big does it have to be to be self regulating? How complex does it have to be. Is simple better or is complex the way to go?

 

Michael