Human overpopulation is the core cause....Earth is like a closed petri dish with finite resources yet some people create FAR more children per family than the 2.O the planet needs. When I was 17 I was made hopeful by the Zero Population Growth movement with the goal of 2.O kids per family but at 61 I've abandoned optimism with so many people cranking out 6, 10, 12 kids as if there was no future those kids would inherit. It does no good to be "green" with token perky recycling permaculture efforts if people won't breed responsibly as if there was an actual future their children will inherit.