That is a valid concern. One of the largest problems with the project was that they planted massive monocultures of single trees. Something that is extremely dangerous as a single parasite, disease, or pest could annihilate hundreds of thousands of square kilometers.

Plus monocultures limit biodiversity to an extreme capacity as the entire forest is suitable only to a very limited number of species. It’s not that the animals aren’t there to begin with, it’s that not many can survive in the mass monoculture forest.