When you look at the Bible, and I read the Bible very seriously, for a lot of my life, I believed the Bible ordained the death penalty, and the Bible seemed to be very clear about that. But the more I look, the more troubled I became because it's not that simple. In the Bible, there's some 30 death-worth crimes, like working on the Sabbath, or disrespecting your parents. Are we that fundamental that we should bring back that death penalty?
The genocide will not necessarily take the form of war, or death camps. Most likely it will take the form of ecocide, in which landscapes are devastated and the populations that live there slowly starve or turn upon each other savagely because there isn't enough food or water to go around.