That's a very good question. There isn't a really good answer, because in every exercise where humans have tried to manage an ecosystem rather than manage human activities, we've basically failed.
The biggest problem is we think we manage ecosystems, but the reality is we manage the human activities around them. There is a balance you can take by looking at predator-prey relationships, but you have to understand those very well before you actually do something. The cases where people have done this kind of predator management have often virtually eliminated the predator, and there's not necessarily been the response that they were expecting from the other species, because we're at the mercy of the environment. Whether the environment is productive or not is probably the biggest unknown that we have to deal with.