How to Colonize an Asteroid
When the ecosystem of the colony reaches the point where it can support human life, special care must be given to the balance of life forms, soil quality, and atmospheric content. The greater the diversity of life inside the colony, the better the chances are that the ecosystem will survive and enter a state of natural balance, kind of like a giant terrarium.
Most plants and animals from earth can be stored in the form of seeds or frozen embryos and released into the ecosystem as it becomes capable of their support. This may be an excellent opportunity to provide a home for some of earth's more endangered species.
It must be stressed that twelve square miles of surface does not create a very large ecosystem, but it should be of sufficiant size to support quite a variety of plants and animals, as long as the biologists keep a close eye on all aspects of the balances between different plants, animals, insects, bacteria, atmospheric gasses, and soil nutrient levels.