I would say immigration only.
emigration would theoretically reduce the genetic variation as unique individuals leave, but immigration would bring unique traits into circulation in an ecosystem.
I'm not super great at biogy tho so this might not be right... :)
<span>Antrophocentric ideas and beliefs involve believing that only human beings and human beings alone are of the utmost importance above all else, that the human self is of the total concern. It is a very "self" oriented set of ideas. Eccocentrists are particularly and primarily focused on the environment, preservation, and "green" movements.</span>