...we still need to conserve our resources, and gradually reduce our population. Otherwise many people will die unnecessarily.Nope. The only sustainable economy is one based on surplus. Without it, many people die unnecessarily. The US isn't all chubby because we're stealing food out of the mouths of subsistence farmers in Africa.
First of all I should say that by “we” and “our” I mean human beings and all nations. So far as I can see the only sustainable economy is one in which the people of the world don’t try to consume more than they produce, and if there is not enough, feel the need to go to war to seize what they cannot buy. Furthermore, an economy based on surplus food in our case does seem to lead to obesity, poor health, and high medical costs, which then reduces our surpluses.