When a species has become extinct in an area and the reason for that extinction has been removed and there is no chance that the species returns independently, reintroduction may be considered.
Because there are all kinds of conditions that must be met in order to reach a healthy population, a reintroduction needs to be closely monitored. One of the pitfalls is to suffice with a one-off release of a group of animals; inbreeding is a factor that may play a major role. It is also important that the area is not too small because a healthy resilient population cannot be too dependent on chance circumstances. (source: Wikipedia)