Maintaining very small ecosystems

If the biosphere-2 team are correct, and it really does require a whole 3
acres to support 8 healthy human beings (1500m2 each), then a colony the
size of island-1 would support only 800-900 people.

The biosphere-2 people weretrying to re-create a wide variety of diverse biomes as seen on Earth. In the agricultural areas of Island One, the only concern would be providing good conditions for growing crops, with conditions probably being a good deal more monotonous. So we might expect greater productivity.
In "The High Frontier", O'Neill said that his original estimates regarding productivity/acre had been looked at by experts in the field and they felt we could probably do even better.

Regards,

Mike Combs