That and reduction in cattle. (And the elephant in the room, that uncomfortable truth: consideration of the number of humans, which we sooner or later will have to address, even though that will be fraught with many ethics issues and is ripe for abuse).
amount of people is irrelevant. Amount of people wanting to live US standard is the problem. Order new shitty clothes 3x a week and other consumption bs? Costs 300x of an average person in the developping world
