Reintroduction, in this context, means trying to establish a population of an animal [or plant] in a natural environment after it has become extinct there. The wolf and the lynx were once native to many areas of the world, from which they have been driven out or hunted to extinction.

That sentence doesn't sound like it was written by a native, but "reintroduction" usually refers to putting an animal back into the wild or back into it's usual habitat after sheltering or helping it in some way. For example: "After nursing the wounded bird back to health, the staff at the zoo reintroduced it into the general population."