As biologists have largely punted the definition of "species", there's really no adequate definition of "human". I find it hard to have an argument when no one will define the principle term!
But why do rights have anything to do with species? Isn't it really about lifestyle, and, specifically the lifestyle of a domesticated animal. Perhaps the prob. is domesticated v wild, not humans v the environment?
Granted there are too many humans, but isn't that like saying the problem with PNW forests is too many Douglas Firs?