You teleport down to the moon and take a look around. There's already lush and brightly colored flora here and strange animals scampering about. Nobody would mistake this for Earth, but it already has many of the same characteristics, and even similar gravity. Your orders said that the biggest obstacle was an agressive species to be cleared out. You get your first indication of what that could be as a stone strike you in the shoulder.
You turn around to see dozens of them armed with sticks and rocks, but you could wipe them all out with one wide ray from your plasma rifle. The problem is that they're yelling something, waving tools, and look vaguely humanoid; this species is clearly sentient. Can you really just exterminate them all to live here?