The problem is that for almost any feature of humanity that you can name, whether it's the ability to suffer, whether it's the capacity to reason, whether it's having lives that can go better or worse, there are at least some other non-human animals that have all of these features as well. So to exclude non-human animals from the range of moral concern but to include all humans, just seems morally arbitrary.
Even if Bill McKibben were to become dictator, future generations would suffer because of the carbon we had already emitted.
I worry that even well-intentioned attempts to "improve nature" (say by reducing suffering) will make things worse even in their own terms.
