I don't think it is necessary to cull the human population, what I think we do need however, is a new system of fairness and global citizenship.

We as a race need to work together not apart, but we need to hit a certain point to make this happen - something, perhaps, similar to what Regan alluded to in his infamous speech about the world coming together to fight a common threat such as Little green martians with antennae hanging iff their heads... Only a matter of time to come together as a race, as we kniw there is water in mars so martians drink water...