Let’s think about the passage in a less abstract fashion. It states: Wildlife experts should not interfere with the habitats of creatures in the wild, because manipulating the environment to make it easier for an endangered species to survive invariably makes it harder for non endangered species to survive.
This argument could be applied to endangered bald eagles and common pigeons. The argument would be saying: Experts should not manipulate the environment to make it easier for bald eagles to live, because that would invariably make it harder for pigeons to survive.
But we might not care about the pigeons not surviving, because pigeons are abundant (and pests!) and therefore it is ok if they don’t survive in that particular habitat. And that is what answer E is saying — the argument takes for granting that preserving the eagle is not more important than preserving the pigeons in that habitat, even though it very well might be.