Here’s a grim thought about the environment.
There is no way of life for humans on Earth that is ecologically sustainable for a global population of more than a billion. Our per capita environmental footprint doesn’t really matter at this stage.
If we retain our current population and return to a Palaeolithic lifestyle, we’re still fucked in the not-too-long run. If we quit having so many children and get back down to a global population in the hundreds of millions, it won’t matter any more how each of us splurges and consumes.
You don’t need to recycle milk cartons. What you really need to do is convince people to have no children. Two good ways to do this is to give all women at least a high school education, and to convince the Catholic Church that contraceptives are a gift from God.
The population will of course come down eventually. We choose whether this will happen by us not having so many children, or by billions of people dying catastrophically.