I think we ought not to be consuming more habitat than is absolutely necessary. And even when we do displace animals, we shouldn't kill them as part of that dislocation. We can't disrespect their value as sentient beings. They have the right not to be interfered with, not to be exploited or killed or tortured. If they have endorphins, which are produced to alleviate pain, then they are sentient.
Earthworms have endorphins.
Fish have endorphins. With higher animals you can usually tell when they're feeling pain. They cry out, or they limp, or whatever. You'd be an idiot not to know when a dog, or cat, or monkey or cow was in pain. It gets a little more difficult when you're talking about earthworms or fish, but there are ways to determine pain, and sentience, in even these animals.